Iceland is the product of coupled interaction between the Mid-Atlantic Ridge (MAR) and the Iceland mantle plume-a unique combination of magmatism and tectonics on modern Earth, but perhaps not in Earth's past. Of particular interest is the petrogenesis of silicic (SiO2 ≥ 65 wt%) magmas in Iceland, their formation amid a manuscript submitted to Journal of Geophysical Research-Solid Earth dynamic oceanic tectonic environment, and possible implications for early continental crust formation (e.g., Willbold et al., 2009;Reimink et al., 2014;cf. Martin et al., 2008;Carley et al., 2014). Icelandic bedrock comprises ~10-15% silicic rocks (e.g. Walker, 1966;Thorarinsson, 1967;Jónasson, 2007), which is unusual when compared to the overwhelmingly basaltic composition of oceanic islands globally. Indeed, the mechanism(s) by which silicic magmas are produced in Iceland are the subject of ongoing debate (e.g., Carmichael, 1964;Óskarsson et al., 1982;Macdonald et al., 1987;Marsh et al., 1991;Sigmarsson et al., 1991;Nicholson et al., 1991;Furman et al., 1992;Jónasson, 1994;Gunnarsson et al., 1998;Prestvik et al., 2001;Bindeman et al., 2012;Banik et al., 2018Banik et al., , 2021;;Carley et al., 2020;and many others).
To provide new insight in this fundamental question of silicic petrogenesis, we utilize in situ U-Pb zircon ages bolstered with zircon trace element and O and Hf isotopic compositions, together with whole rock Nd, Hf, and Pb isotope compositions, from two central volcanoes at Hrafnsfjörður and Árnes and an isolated silicic unit at Kaldalón, to
(1) investigate the petrogenesis of silicic magmas early in Iceland's history, (2) illustrate shortcomings in the current paradigm for spatial-temporal geodynamic evolution of northwestern Iceland, and (3) support a model whereby a pulsing mantle plume exerts strong control on the isotopic composition of Iceland's earliest preserved silicic history.
The Iceland plume has existed since at least ~60 Ma and is implicated in the opening of the North Atlantic (e.g., Bjarnason, 2008;Lawver & Müller, 1994). The MAR separating the North American and Eurasian plates and the Iceland plume were initially independent of one another, but because the MAR axis moves northwest at ~1-3 cm/yr manuscript submitted to Journal of Geophysical Research-Solid Earth while the Iceland plume remains functionally stationary (e.g,. Müller et al., 1998;Torsvik et al., 2001), the resulting surface expression of the Iceland plume moved (in the MAR reference frame) southeast under the MAR axis and then progressively east of it (Lawver & Müller, 1994). The MAR and plume became coupled ~25 Ma, which led to abnormally high rates of magma production and the construction of Iceland and its oceanic plateau (e.g., Bjarnason, 2008;Brandsdóttir & Menke, 2008).
The MAR around Iceland is exposed on land as a series of rift zones because it has repeatedly relocated east of the main rift axis to remain coupled with the plume (Fig. 1). The plume periodically recaptures the rift through a rift relocation, or rift jump, which moves the rift eastward (Harðarson et al., 2008). The oldest rocks in the northern Westfjords are proposed to have originated from the oldest rift associated with Iceland, the Northwest Rift Zone (NWRZ; Fig. 1), during the latter stages of the rift's active lifetime (~24-15 Ma) (Hardarson & Fitton, 1997;Hardarson et al., 1997). Sometime before 15 Ma, another rift, the future Snaefellsnes-Skagi Rift Zone (SSRZ; Jordan et al., 2019 also list several alternate names), began to propagate ~100 km to the southeast to remain coupled with the plume center (e.g., Hardarson et al., 1997;Martin et al., 2011). Martin & Sigmarsson (2011) hypothesized that the NWRZ-to-SSRZ transition trapped a portion of older oceanic crust between the two rift axes, which implies the position of the trapped crust-if it exists-is directly under the Westfjords. (rifts, 1-4) or dashed (fracture, 5) lines. Neovolcanic zones (VZ) demarcated by stippled areas (a=Reykjanes Peninsula [RP]; b=WVZ; c=EVZ; d=NVZ; e=SIVZ; f=Snaefellsnes volcanic belt (SVB); g=Öraefi volcanic belt (ÖVB)). Approximate mantle plume surface expression (Wolfe et al., 1997) outlined with dashed circle.
Magmatism appears to have shifted from the extinct NWRZ to the SSRZ around 14.9 Ma (Harðarson et al., 2008;Hardarson et al., 1997;Martin et al., 2011). Both
Hrafnsfjörður and Árnes magmas likely erupted from the SSRZ based on regional dip direction and paleomagnetic ages of coeval rocks (Jordan et al., 2013 and references therein; this study). The proximity of both volcanoes to the projected NWRZ rift axis (e.g., Harðarson et al., 2008) suggests that Hrafnsfjörður and Árnes may unconformably manuscript submitted to Journal of Geophysical Research-Solid Earth overlie basalts erupted from the NWRZ toward the middle-to-end of that rift's life.
Extensive stratigraphic mapping, accompanied by paleomagnetic and K-Ar geochronologic analysis, of lava sequences in Westfjords by McDougall et al. (1984) demonstrated the uniform growth rates of the Tertiary basalts that the majority of the Westfjords comprise. A lava succession in the western region of the Westfjords ranged from 14.0 to 11.9 Ma, with an average eruption interval of 5 kyr, while a stratigraphic sequence of lavas along northeastern coast of the Westfjords, trending south from Árnes, erupted from 12.7 to 8.0 Ma with an average eruption interval of ~12 kyr (McDougall et al., 1984). Both of these profiles demonstrate a decrease in age in the regional dip direction toward the proposed paleo-rift axis. Magmatic activity associated with the SSRZ continued until ~6.7-5.5 Ma (Harðarson et al., 2008;Martin et al., 2011). Martin et al. (2011) propose that the currently active Northern Rift Zone (NRZ) began propagating ~200 km east of the SSRZ around 13 Ma, and the SSRZ and NRZ simultaneously operated until the SSRZ's demise (cf. Harðarson et al., 2008).
Hrafnsfjörður (alternatively spelled 'Hrafnfjörður') and Árnes central volcanoes are located in the northern and eastern Westfjords of Iceland, respectively (Fig. 1; Supplemental Figure S1). Both volcanoes are composed dominantly of basalt lavas with volumetrically significant intermediate and silicic rocks. Hrafnsfjörður has ~25% dacite and ~15% andesite exposure, with the remainder basalt; Árnes has ~5% andesite, 1% dacite, and >20% rhyolite exposure in addition to interlayered, coeval basalt (Jordan et al., 2013;Jordan & Olin, 2008;Supplemental Figure S1). We also identified silicic rocks manuscript submitted to Journal of Geophysical Research-Solid Earth from Kaldalón-an area that potentially represents a central volcano but is largely hidden beneath the glacier Drangajökull and thus lacks detailed examination. Silicic rocks from Hrafnsfjörður and Árnes are medium-to dark grey lavas, aphanitic with sparse phenocrysts of plagioclase and pyroxene, and show varying degrees of visible alteration from none to moderate with mild secondary mineralization. The rocks from Kaldalón are more porphyritic and altered to a reddish color but have largely the same mineralogy (Table 1). Due to the limited exposure, stratigraphic emplacement of Kaldalón materials is difficult to discern beyond the immediate ~20 m around the sampling area. These volcanic centers were chosen for study based on: (1) their geographic location in one of the oldest parts of Iceland; (2) their comparatively large volumes of intermediate and silicic magmas that maximize likelihood of obtaining zircon for geochronology studies;
(3) the rare opportunity to investigate petrogenesis at Kaldalón, which is largely obscured by the icecap Drangajökull; and (4) the sizes of Árnes and Hrafnsfjörður as the two largest central volcanoes in the northern Westfjords. We focus on analyses of zircon because it provides a reliable age of magmatic crystallization. Furthermore, hydrothermal alteration is ubiquitous in the Icelandic crust, but zircon strongly resists chemical weathering and diffusive exchange (e.g., Hoskin and Schaltegger, 2003;Valley, 2003) and is therefore more likely to retain evidence for the geochemical characteristics of parent melt compositions compared to whole rock or other mineral phases.
Geologic maps of Árnes and Hrafnsfjörður (Jordan et al., 2013) informed the sampling strategy (Supplemental Fig. S1). We collected at least one sample from each major rhyolite unit mapped at Árnes, as well as one andesite unit that did not yield zircon (Tables 1, S6). At Hrafnsfjörður, samples were obtained from a dacite dome and a previously unsampled and unmapped silicic unit of unknown origin (Table 1). The ages from sample KK-24 were initially documented by Jordan et al. (2013). Two silicic units were sampled at Kaldalón. Three to five kg of each sample was returned to Vanderbilt University for processing.
Fresh rock slices, with weathered or visibly altered materials removed, were cut into billets and powdered in stainless steel in preparation for whole rock petrographic and geochemical analysis, respectively. Whole rock major and trace element methods and results are listed in Supplemental Table S6. Zircon was separated from two Hrafnsfjörður, six Árnes, and two Kaldalón rock samples using standard crushing, sieving, magnetic, and density separation techniques, followed by hand picking under a binocular microscope. After casting in epoxy, zircon grains were polished to expose grain manuscript submitted to Journal of Geophysical Research-Solid Earth interiors and imaged using the Vanderbilt University EES Tescan Vega 3 LM variable pressure scanning electron microscope (SEM) using cathodoluminescence (CL) prior to obtaining in situ zircon analyses.
Zircon analyses were conducted in the following order: O isotopes, trace elements, U-Pb geochronology, and finally Hf isotopes. Values >2 standard deviations from the mean or interpreted as the result of faulty analysis were not used in calculation of weighted mean crystallization ages, δ 18 O, or εHf values
We obtained zircon δ 18 O isotope compositions at the University of California-Los Angeles using a CAMECA ims-1270 secondary ion mass spectrometer (SIMS) and following the methods of Trail et al. (2007). Operating conditions were the same as those given in Banik et al. (2018). R33 (δ 18 O = 5.55 ± 0.08‰, 2SD; Black et al., 2004) was the primary zircon isotopic standard. External 2σ reproducibility for R33 analyses ranged from 0.37 to 0.79‰ for all data obtained from Hrafnsfjörður ("HfE"), Árnes, and Kaldalón samples. Previously published data for Hrafnsfjörður sample KK-24 had external R33 2σ reproducibility of 0.67‰ (Carley et al., 2020). Five zircon oxygen isotope analyses from sample ÁrE1 were obtained at the University of Wisconsin-Madison WiscSIMS facility via a CAMECA ims-1280 secondary ion mass spectrometer following the method of Kita et al. (2009). Operating conditions were the same as those described by Banik et al. (2021). Measured ratios were corrected for mass discrimination using primary zircon standard KIM-5 (δ 18 O = 5.09 ± 0.12‰, 2SD; Valley et al., 1998), which had 2-sigma reproducibility ranging from 0.15 to 0.24‰. All data are reported as δ 18 O calculated relative to VSMOW (Baertschi, 1976). Overall uncertainties ( Carley et al. (2020). Age from Jordan et al. (2013) and Carley et al. (2020).. **Uncertainty is 2SD since only one grain was analyzed typesetting))
Table 2. Summary of weighted sample means (U-Pb geochronology and Hf isotopes), medians (O isotopes), and other statistics from in situ analyses of Árnes, Hrafnsfjörður, and Kaldalón zircon. Age and oxygen isotope data for samples DH-08 and DH-15 are pooled.
In situ zircon trace element compositions and ages were obtained using the U.S.
Geological Survey-Stanford University sensitive high-resolution ion microprobe with reverse geometry (SHRIMP-RG). Zircon mounts were re-imaged via CL and lightly polished to remove topography and Cs + implantation from the δ 18 O analytical procedure prior to additional analysis. Operating conditions for all samples except HfE2 and HfE3 manuscript submitted to Journal of Geophysical Research-Solid Earth included an O2 -primary ion beam focused to a ~25x17 µm diameter analytical spot for U-Pb isotope determination and a ~12x12 µm diameter analytical spot for trace element analyses. Hrafnsfjörður samples HfE2 and HfE3 were analyzed using a routine that combined U-Pb age and a limited number of trace elements in a single analysis using a ~25x25 µm diameter analytical spot. U-Pb ages were calibrated using zircon standard R33 (age=419 Ma; Black et al., 2004) and zircon trace element concentrations were standardized relative to MAD-559 (Coble et al., 2018). Squid 2.51 (Ludwig, 2009) and Isoplot 3.76 software (Ludwig, 2012) were used to reduce data. Corrections for 230 Th disequilibrium were undertaken using whole rock Th/U values for each sample to assume an initial ( 230 Th/ 238 U)melt value, which typically resulted in a correction of 80-100 kyr.
Measured 206 Pb/ 238 U data were corrected for common Pb using measured 207 Pbc based on a model Pb composition from Stacey and Kramers (1975). Not all grains were analyzed for both U-Pb ages and trace elements.
After trace element and U-Pb analysis, zircon mounts were re-imaged via CL.
Lutetium-Hf isotope compositions were then measured on a subset of the same grains using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICPMS) at the Radiogenic Isotope and Geochronology Laboratory (RIGL) at
Washington State University. Analyses were performed using a ThermoFinnigan Neptune MC-ICPMS coupled to a New Wave 213 nm Nd-YAG laser with an analytical spot diameter of ~40 μm. Lutetium-Hf isotope compositions were analyzed on 34 grains from four Árnes samples (ÁrE1, ÁrE3, ÁrE4, and DH-04). Additionally, 19 grains from two Hrafnsfjörður (HfE2 and HfE3) and two Kaldalón (KlE1 and KlE2) samples were manuscript submitted to Journal of Geophysical Research-Solid Earth analyzed using a Thermo Scientific Neptune Plus MC-ICPMS coupled to a Teledyne Analyte Excite 193 nm excimer laser with an analytical spot diameter of ~40 μm. We follow the instrument configuration, operating parameters, and data reduction methods outlined by Fisher et al. (2014), with the exception that U-Pb ages were not simultaneously determined. Details on the analytical procedure and standard analyses are in Supplemental Table S8. Calculation of present day εHf values utilized CHUR parameters ( 176 Hf/ 177 Hf=0.282785) reported by Bouvier et al. (2008). It is common to report present day εHf values when dealing with Icelandic materials due to their geologically young (<15 Ma) ages (e.g., Kitagawa et al., 2008) and corresponding small evolution away from CHUR (i.e., ~0.3 εHf units or less). 2.5 Whole rock Nd, Hf, and Pb isotope analysis Whole rock Nd, Hf, and Pb isotope compositions were measured at the RIGL at Washington State University on a Thermo-Finnigan Neptune MC-ICP-MS using the procedure outlined by Gaschnig et al. (2011). Powders intended for Pb analysis underwent leaching in 6N HCl prior to dissolution. Whole rock Hf isotope analyses were corrected for mass fractionation using 179 Hf/ 177 Hf = 0.7325 and normalized using Hf standard JMC475 ( 176 Hf/ 177 Hf = 0.282160; Vervoort & Blichert-Toft, 1999). JMC-475 had measured 176 Hf/ 177 Hf = 0.282132 ± 0.000007 (2σ standard deviation (SD)) which resulted in a correction factor of 1.000093. Mass fractionation during Nd isotope analyses was corrected using 146 Nd/ 144 Nd = 0.7219 and normalized using a correction factor of 1.000052 based on our measured value of 143 Nd/ 144 Nd = 0.511831 ± 0.000014 (2σ SD) of the La Jolla Nd standard ( 143 Nd/ 144 Nd = 0.51185; Lugmair et al., 1983). All epsilon values were calculated using present-day ratios and CHUR values of 176 Hf/ 177 Hf = manuscript submitted to Journal of Geophysical Research-Solid Earth 0.282785 and 143 Nd/ 144 Nd = 0.512630, as reported by Bouvier et al. (2008). Mass bias in the whole rock Pb isotope analyses was corrected for using 205 Tl/ 203 Tl = 2.388 and we normalized the mass bias corrected values for standard NBS 981 using 206 Pb/ 204 Pb = 16.9405, 207 Pb/ 204 Pb = 15.4963, 208 Pb/ 204 Pb=36.7219 (Galer & Abouchami, 1998). Our measured NBS 981 values, with 2σ SD, were: 206 Pb/ 204 Pb=16.9361±0.0010, 207 Pb/ 204 Pb=15.4924±0.0008, and 208 Pb/ 204 Pb=36.7016±0.0018.
For context, petrographic observations and whole rock major and trace element compositions are reported in Supplemental Tables S5 and S6, respectively. All samples are metaluminous and range from basaltic-andesite to rhyolite, follow the tholeiitic series
trend, and have quartz-normative CIPW norm compositions. Samples are generally sparsely porphyritic with variable amounts of <1-2 mm plagioclase and clinopyroxene (plag>cpx) phenocrysts and subordinate FeTi-oxides. Orthopyroxene is present in 2 of 3 Hrafnsfjörður "HfE" samples but absent in Árnes samples. Plagioclase grains commonly display intricate zoning, sieve textures, resorption, and other evidence of disequilibrium conditions. 3.2 Zircon geochronology U-Pb geochronology results are shown in Fig. 2a, summarized in Table 2, and presented with full analytical details and results in Supplemental Table S1. Weighted mean crystallization ages are reported with 2SE uncertainty. manuscript submitted to Journal of Geophysical Research-Solid Earth The weighted mean crystallization ages for Hrafnsfjörður samples include Hrafnsfjörður 13.7±0.2 Ma (MSWD=1.1; n=10) for HfE2; 13.9±0.2 Ma (MSWD=2.7; n=23), for sample HfE3; 14.3±0.1 Ma (MSWD=0.7; n=0.14) for KK-24. Analysis of a single HfE3 grain with a potentially inherited core (based on textures revealed by CL imaging; Supplemental Fig. S2) yielded a date of ~16.3 Ma. Although Kaldalón samples KlE1 (14.1±0.4 Ma; n=12) and KlE2 (13.6±0.5 Ma; n=10) have weighted mean crystallization ages within the same range as the Hrafnsfjörður samples, they have slightly higher MSWDs (3.1 and 2.5, respectively). 304 manuscript submitted to Journal of Geophysical Research-Solid Earth MSWD values higher than what would be expected for a homogeneous population (e.g., Mahon, 1996; ~2 for the given sample sizes) are interpreted to represent several stages of zircon crystallization.
Trace element compositions in zircon are summarized in Fig. 3, with full analytical results in Supplemental Table S2. Zircon compositions from all three volcanic centers span similar ranges (Fig. 3). Hrafnsfjörður and Árnes zircon grains are particularly similar: both have Ti ranging from ~4 to 20 ppm; Hf also ranges similarly, from ~7,000 to 12,000 ppm for Árnes and 7,000 to 14,000 ppm for Hrafnsfjörður.
Titanium analyses from grains with >10 ppm Fe or anomalously high Ti (>30 ppm) were manuscript submitted to Journal of Geophysical Research-Solid Earth excluded from further interpretation due to likely contamination by inclusions of nonzircon phases. Uranium concentrations range from ~50 to 900 ppm at Hrafnsfjörður and 9 to~700 ppm U at Árnes, with Th/U from ~0.3 to 1.1 at both locations. Zircon grains from Kaldalón have a more restricted range of compositions: ~4 to 13 ppm Ti, with all but one analysis <9 ppm; ~8,000 to 12,000 ppm Hf; ~50 to 250 ppm U, with one outlier containing 494 ppm U; and Th/U from ~0.3 to ~1.0. Two Kaldalón outliers have elevated Th/U (~1.5) as well as U/Yb (~0.4). Árnes samples display a lower and more restricted range of Yb/Gd (4.7-13.8; median=8.6) than zircon from older Hrafnsfjörður (6.5-26.8; median=12.7) or Kaldalón (4.8-16.6; median=13.2)(Fig. 3a). Additional zircon trace element data are available in Supplemental Table S2. Element ratios are highlighted to illustrate potential differences in the zircon parental melt compositions or petrogenesis.
For example, U/Yb in zircon mirrors parental melt compositions (Grimes et al. 2015); order-of-magnitude differences between the highest and lowest values at Hrafnsfjörður suggest zircons from at least two different parent melts are represented. Degree of fractionation of the parent melt may also be assessed with other trace elements, such as Hf (Claiborne et al., 2006;Grimes et al. 2015). Variations between heavy, middle, and
Oxygen isotope compositions (δ 18 OVSMOW) in zircon (n=37 from Hrafnsfjörður; n=74 from Árnes; n=24 from Kaldalón) are summarized in Fig. 2b and
Table 2, with full analytical results in Supplemental Table S3. Hrafnsfjörður zircon ranges from δ 18 O~2.7 manuscript submitted to Journal of Geophysical Research-Solid Earth to 4.3‰; Árnes zircon from ~2.1 to 4.2‰; and Kaldalón from δ 18 O~1.2 to 3.6‰. With the exception of Hrafnsfjörður sample KK-24, grains from each individual sample
display a high degree of oxygen isotopic variability (Fig. 2b). Weighted sample means range from 3.1±0.2 to 3.5±0.1‰ (2SE) at Árnes, from 3.5±0.2 to 4.0±0.4‰ at Hrafnsfjörður, and from 2.1±0.2‰ to 2.9±0.4‰ at Kaldalón (Fig. 2b). All zircon samples are isotopically light compared to mantle-equilibrated zircon (δ 18 O=5.3±0.6‰; Valley, 2003). Iceland zircon δ 18 O commonly ranges between +2 and +4‰ (Carley et al., 2014(Carley et al., , 2020)), as do the majority of grains from this study. Median and average δ 18 O from a compilation of >700 neovolcanic and Tertiary zircon analyses across Iceland (Banik et al., 2021;Carley et al., 2020) are 3.1‰ and 2.8‰, respectively.
Hafnium isotope compositions from Hrafnsfjörður, Kaldalón, and Árnes zircon grains are listed in Fig. 2c and Table 2, with full analytical results in Supplemental Tables S4 and S8. Hrafnsfjörður samples KK-24 and HfE3 have among the most radiogenic zircon compositions reported in Iceland (εHf ~10 to 17; Carley et al., 2020). Icelandic zircon has median εHf=+13.5, with 75% of grains having εHf<+14.5 and 95% of grains having εHf<+14.5 (n=457; Carley et al. 2020;Banik et al. 2021). Zircon εHf in HfE3 ranges from +14.6±1.6 to +17.3±1.1 with a weighted sample mean of εHf=+16.0±0.5 (2SE, as are all reported εHf uncertainties in this section; Fig. 2c) (n=7; MSWD=0.5), while zircon εHf in KK-24 ranges from +14.4±1.1 to +17.0±2.1 with a weighted sample mean εHf=15.6±0.4 (n=14; MSWD=1.2) (Fig. 2c) (Carley et al. 2020). Epsilon Hf values in zircon from Hrafnsfjörður sample HfE2 range from +14.4±1.2 to +16.3±1.3, with a weighted mean of +15.3±0.7 (n=3; MSWD=0.6). Kaldalón zircon grains are similar with manuscript submitted to Journal of Geophysical Research-Solid Earth respect to Hf isotope compositions, with εHf ranging from +14.3±1.1 to +16.2±1.4 and weighted means of +15.5±0.5 (KlE1; n=5; MSWD=0.3) and +14.8±0.6 (KlE2; n=4; MSWD=0.3). Árnes zircon (n=34) from four samples range from εHf=+11.3±1.1 to +14.7±1.6. Árnes samples ÁrE3 and ÁrE4 have weighted sample means of εHf=+12.7±0.4 (n=15; MSWD=1.5) and +13.0±0.5 (n=15; MSWD=1.6), respectively, with sample DH-04 having slightly lower weighted mean εHf (+11.8±0.9; n=3; MSWD=0.5). Only one zircon from sample Áre1 (εHf=+12.4±1.7) was analyzed due to crystal size limitations. 3.6 Whole rock Hf, Nd, and Pb isotope compositions Neodymium, hafnium, and lead isotopic ratios for four Árnes and three Hrafnsfjörður whole rock samples are within established ranges for Icelandic rocks (Fig. 4; Supplemental Table S6) (e.g., Harðardóttir et al., 2022 and references therein . Árnes and Hrafnsfjörður rocks have 143 Nd/ 144 Nd ratios ranging from 0.513011 to 0.513055 (eNd +7.3 to +8.1), while 176 Hf/ 177 Hf ratios range from 0.283135 to 0.283211 (eHf +12.8 to +15.1). Árnes and Hrafnsfjörður samples plot approximately on or above the Hf-Nd terrestrial array of Vervoort et al. (2011) (Fig. 4a) and occupy two sub-fields: one more radiogenic, with eHf >+14.5 (all Hrafnsfjörður samples, plus Árnes sample ÁrE1), and one less radiogenic, with eHf <+13.4 (remainder of Árnes samples). The more radiogenic sub-group correlates with compositions of modern Northern volcanic zone (NVZ) rocks (Fig. 1), while the less radiogenic sub-group has compositions most similar to rocks from the modern Eastern volcanic zone (EVZ) and South Iceland volcanic zone (SIVZ), (e.g., Peate et al., 2010;Harðardóttir et al., 2022).
Icelandic volcanic rock compositions extend to both sides of the Northern Hemisphere Reference Line (NHRL; Hart, 1984) on a 208 Pb/ 204 Pb vs. 206 Pb/ 204 Pb diagram (Fig. 4b). Hrafnsfjörður and Árnes samples each occupy a relatively restricted area in Pb-Pb compositions-the two Hrafnsfjörður samples HfE2 and HfE3 yield 206 Pb/ 204 Pb=18.34 and 18.35, 207 Pb/ 204 Pb=15.47 for both, and 208 Pb/ 204 Pb=37.95 and 37.96. The four Árnes samples ÁrE1, ÁrE2, ÁrE3, and ÁrE4 have 206 Pb/ 204 Pb=18.64-18.78, 207 Pb/ 204 Pb=15.48-15.49, and 208 Pb/ 204 Pb=38.34-38.48 (Fig. 4b-d). Similar to trends observed in Hf and Nd isotopic compositions, Pb-isotope ratios of Hrafnsfjörður rocks generally follow those of the modern NVZ; Árnes samples have Pb-isotope compositions common to rocks from a number of volcanic locations, most notably the NVZ, SIVZ, and EVZ. indicates area of main Fig. 4c; Northern Hemisphere Reference Line (NHRL) of Hart (1984) is shown. (d) εNd vs. 206 Pb/ 204 Pb.
Three major points of discussion arise from the data described above: the first involves the ages of Hrafnsfjörður and Árnes zircons and implications for a seemingly paradoxical spatial-temporal evolution of the Westfjords; the second centers upon the petrogenetic mechanisms by which these Westfjords silicic magmas formed; and the third relates to the isotopic compositions observed in these rocks and their potential role in deciphering the afore-mentioned spatial-temporal paradox of Westfjords evolution and Icelandic crustal evolution overall.
Hrafnsfjörður is the oldest known silicic central volcano in Iceland, with zircon ages suggesting silicic magma activity from ~14.3 to 13.7 Ma. A regional plateauforming basalt from ~300 m under the silicic succession yielded an Ar/Ar age of 14.20±0.33 Ma (Jordan et al., 2013). Kaldalón silicic magmatism is of similar age and duration (~14.1 to 13.6 Ma). Árnes is younger, though with similar duration, with zircon crystallization sample ages from ~13.1 to 12.8 Ma. However, at least four grains from samples ÁrE3 and ÁrE1 seem to correlate well in age with grains from Hrafnsfjörður sample KK-24. Multiple episodes of zircon crystallization are evident at all three locations based on MSWDs >~2 and supported by intragrain CL textures. The only other
Icelandic systems with silicic units reported to approach these ages are in the Eastfjords, with ages in the range of ~13.4 to 12.9 Ma (Carley et al., 2017;Martin et al., 2011).
manuscript submitted to Journal of Geophysical Research-Solid Earth
Basalt lavas in the Strandir region of the Westfjords that encompasses Árnes have ages as old as 12.7 Ma (McDougall et al. 1984).
Silicic magmatism at all three sampled centers appears to have lasted 500 kyr or more, with basaltic magmatism likely extending each system's lifetime. Due to limited sampling, it should be emphasized that these are minimum estimates of system longevity.
Central volcanoes in Iceland generally have lifespans from ~300 kyr to ~1.5 Myr based on whole rock data (e.g., Saemundsson, 1979;Hardarson et al. 2008), but the longest reported lifespans when taking zircon ages into account are >2 Myr (Banik et al., 2018;Carley et al., 2017). Each individual whole rock sample also shows an apparent range of at least a few hundred kyr in zircon crystallization ages-a common phenomenon observed globally in zircon-bearing systems (e.g., Reid et al., 1997;Lowenstern et al., 2000;Miller and Wooden, 2004;Bacon and Lowenstern, 2005;Simon & Reid, 2005;Charlier et al., 2005;Walker et al., 2007;Claiborne et al., 2010; and many others).
Previous zircon-based studies in Iceland suggest that silicic magmas reside in nearsolidus to sub-solidus conditions prior to being rejuvenated or erupted (Carley et al., 2011(Carley et al., , 2014(Carley et al., , 2017(Carley et al., , 2020;;Padilla et al., 2016;Banik et al., 2018Banik et al., , 2021;;cf. Martin et al., 2011), which is congruent with prevailing perspectives about silicic magma generation in Iceland based on whole rock data (e.g., Jónasson 2007, and references therein).
In order to develop a working model for the geodynamic and petrologic evolution of the Westfjords, we must first confront a number of knowns and unknowns about this manuscript submitted to Journal of Geophysical Research-Solid Earth oldest region in Iceland. Among them include: the location of the SSRZ, the spreading rate of the SSRZ, the location of volcanoes relative to the SSRZ at the time of magmatic activity, and the timing of magmatic activity associated with the SSRZ.
The nature and location of the paleo-rift from which the Westfjords rocks erupted is somewhat speculative. For example, the SSRZ rift axis location has generally been inferred from the location of the on-land Húnaflói-Skagi synform (Saemundsson, 1974).
However, formation of this synform may not necessary require a paleo-rift axis (Garcia et al., 2003). A large amount of uncertainty regarding the location of past rifts if synforms are not reliable indications of the location of paleo-rift axes or spreading history and additional analysis may be required. To provide additional constraint on the nature of rifting in the Westfjords, paleostress analysis presented by Gudmundsson et al. (1996) suggests that the rift zone active in the Westfjords had an ENE axial trend in the southern part but a NNE axial trend in the northern part, and that two extensional trends were present. Further, Bergerat and Angelier (1998) argue that the extinct SSRZ cannot be reconstructed directly through geological mapping thereby highlighting (1) the importance of integrating knowledge of paleostress regimes into this area of research and
(2) the difficulty in estimating the exact location of volcanic system in relation to rift axis back in time.
Though approximate at best, the SSRZ location estimated using a combination of dip direction of the basalt pile, paleomagnetic orientation, and bathymetric profiles in the Iceland plateau and offshore (e.g., Hardarson et al., 1997) provides a starting point for considering the tectono-magmatic history of the rift and its associated region. manuscript submitted to Journal of Geophysical Research-Solid Earth 4.2.1.2 Spreading rate of SSRZ Numerous studies (e.g., Benediktsdóttir et al., 2012;Hey et al., 2010;Saemundsson, 1979;Sigmundsson, 2006) estimate the half-spreading rates of the Icelandic rift zone and the North MAR to be 0.9-1 cm/yr. Major variations in spreading rate are unusual in Iceland through space and time (e.g., Martin et al., 2011). Thus, a half-spreading rate of 1 cm/yr appears to be reasonable for dynamic reconstructions of the Westfjords.
Based on published maps (Jóhannesson and Saemundsson 2009a,b;Harðarson et al., 2008) supplemented by field maps (Fig. S1), we interpret the extents of the Árnes and Hrafnsfjörður volcanic systems to be within the grey regions demarcated in Fig. 1. Based on observations of modern Icelandic volcanoes (e.g., Askja and Krafla in the NVZ), we make the simplified assumption that magmatic systems are centered on or next to the axis of their associated rift. Modern volcanic systems such as Hekla and Katla in the SIVZ produce significant amounts of silicic magma and are located 10s of km from the ERZ rift axis, challenging our assumption that the Westfjords volcanoes examined here would be forming near the SSRZ rift axis. However, it is important to note that Hekla lies on the South Iceland Seismic Zone (SISZ) that connects to the ERZ, resulting in subsurface structure and rhyolite petrogenesis that are unusual compared to other active systems in Iceland (e.g., Geist et al., 2021;cf. Sigmarsson et al., 1992a). Similarly, both Hekla and Katla erupt transitional alkalic magmas indicative of flank zones and rift propagation in modern Icelandic systems (e.g., Jakobsson et al., 2008), whereas Árnes and Hrafnsfjörður rocks have tholeiitic compositions typically associated with eruption from an established rift zone. While these differences do not preclude Hrafnsfjörður and Árnes from manuscript submitted to Journal of Geophysical Research-Solid Earth potentially having the type of spatial relationship that Hekla or Katla has to its parent rift, the geochemical characteristics of these modern systems suggest that they might be too unusual to serve as fitting analogues for extinct systems, and our decision to assume a position central to the rift to be sound.
The timing of SSRZ initiation is dated to 14.9 Ma (Hardarson et al., 1997) and its extinction is constrained between 6.7 Ma and 5.5 Ma (Martin et al., 2011). U-Pb zircon ages indicate that Árnes (silicic activity ~13.1-12.8 Ma), Kaldalón (~14.1 to 13.6 Ma),
and Hrafnsfjörður (~14.3-13.7 Ma) magmatic systems were actively evolving and erupting from the SSRZ fairly early in its lifetime.
Based on the location of the SSRZ presented in Fig. 5 (Harðarson et al., 2008;Martin et al., 2011), using a 1 cm/yr half-spreading rate along a simple linear rift, and assuming that volcanic systems were immediate next to the rift axis, we reconstructed the rift-drift motion of Árnes and Hrafnsfjörður volcanoes (Fig. 5). If the youngest dated silicic unit at Hrafnsfjörður (HfE2) was near the rift axis during active silicic magmatism and the half-spreading rate was 1 cm/yr, Hrafnsfjörður and the now-extinct SSRZ axis should be separated by ~70 to 82 km (depending on exact timing of rift and volcano extinction). The approximate center of Hrafnsfjörður central volcano-and the location of its youngest dated unit-lies ~67 km west of the SSRZ axis based on perpendicular spreading, and ~78 km west of the SSRZ axis if the spreading direction is a 30° offset from perpendicular, as has been suggested for parts of the MAR around Iceland (Benediktsdóttir et al., 2012). This matches the distances we measure well (Fig. 5).
If we assume an average half-spreading rate of 1 cm/yr, and assuming the youngest silicic unit at Árnes (~12.8 Ma) was emplaced near the rift axis, we expect manuscript submitted to Journal of Geophysical Research-Solid Earth
Árnes to be ~61 to 73 km from the SSRZ axis. The approximate location of Árnes' youngest unit lies between ~40 km and ~46 km from the SSRZ axis assuming perpendicular and 30° offset from perpendicular spreading, respectively. This result does not match the expected rift-drift distance between Árnes and the SSRZ axis (Fig. 5). Even ~10 km deviations in location of the axis or the placement of the approximate center of magmatism cannot account for the 15-25 km difference in the measured and expected distances. Further complicating the magmato-tectonic conditions of this is the position of Hrafnsfjörður relative to Árnes. Given the age difference between the youngest dated units from Hrafnsfjörður (HfE2; ~13.7 Ma) and Árnes (ÁrE4; ~12.8 Ma), a halfspreading rate of 1 cm/yr should result in Hrafnsfjörður being located ~10-15 km west of Árnes. In reality, the east-west difference between the two system centers is ~31 km.
The reason for these apparent discrepancies between age and position is not immediately apparent. It may be that the early SSRZ was 10s of km wide and structurally resembled the modern NRZ with its overlapping volcanic systems and extensive fissuredominated systems (e.g., Thordarson & Larsen, 2007). This would have allowed for formation of volcanic systems 10s of km apart. However, the lack of preservation of the fissure swarms associated with the central volcanoes in this study and lack of detailed exploration of many of the region's extinct volcanic systems renders discussion about the true extent of each system or the width of the SSRZ speculative at best. The NRZ is currently linked to the Kolbeinsey Ridge by the ~100 km-long Tjörnes fracture zone and may therefore be strongly influenced by the greater tectonic regime of Iceland and the north Atlantic-conditions that would not have existed at the present magnitude when the Westfjords systems were actively forming in the SSRZ because the offset to the MAR manuscript submitted to Journal of Geophysical Research-Solid Earth system was shorter. Transform faults have been an instrumental component in rifting throughout Iceland's history; earthquakes still occur along these ancient faults (e.g., Einarsson, 2008). However, more work in the Westfjords is needed to shed light on the importance of transform faults in the region's past.
When confronted with Icelandic anomalies and enigmas such as this, several authors (e.g., Foulger, 2006;Martin et al., 2011) have suggested that older crust trapped between rift axes during rift relocation and subsequently covered by newly-erupted lava may be responsible. Trapped extant crust sections would thus produce discrepancies between overall spreading rate, distances between rocks of similar ages, etc., as illustrated by Martin et al. (2011). Specifically, several studies have explored the idea that a piece of the Jan Mayen Microcontinent (JMM), a deformed piece of continental lithosphere resulting from Paleogene rifting of Greenland and Eurasia and opening of the North Atlantic (e.g., Gaina et al., 2009), could be trapped under Iceland (e.g., Foulger, 2006;Torsvik et al., 2015). However, it is unlikely that a rifted piece of the JMM is tectonically pinned and buried beneath lavas in the Westfjords, since isotopic compositions of Westfjords rocks (this study; Hanan & Schilling, 1997) lack the continental isotopic characteristics inferred for southeastern Iceland where the presence of JMM lithosphere has been suggested (Torsvik et al., 2015). Martin et al. (2011) hypothesize that a piece of older oceanic crust was trapped in the Westfjords region during the NWRZ to SSRZ transition. These authors did not specify the exact location or extent of the hypothetical trapped crust, but seismic estimates of crustal thickness suggest an area of slightly thickened crust in the Gláma area of the central Westfjords (Fig. 5) (Darbyshire et al., 2000;Kaban et al., 2002). This manuscript submitted to Journal of Geophysical Research-Solid Earth area is >30 km from Árnes and even farther from Hrafnsfjörður, but the possibility of trapped crust influencing petrogenesis elsewhere along the SSRZ cannot be ruled out.
Determining the geochemical influence of such a crust would be challenging based on the chemical and isotopic similarities between typical oceanic crust and basaltic rocks that predominantly result from plume-rift interaction in Iceland. However, zircon Hf isotope compositions and O isotope compositions from whole rock and zircon may provide insight into this matter.
Oxygen isotope compositions of zircon reflect the compositions of their parental melts and the sources of those melts (e.g., Schattel et al. 2014;Bindeman et al. 2008;Valley 2003; and many others). Icelandic magmas-basaltic and silicic-are commonly reported to have low δ 18 O relative to normal mantle values. Although the Icelandic mantle has been proposed to contain a major component that is depleted in 18 O relative to typical mantle (Macpherson et al., 2005;Rasmussen et al., 2022;Thirlwall et al., 2006;Winpenny & Maclennan, 2014), especially over short length scales,. However, recent examination of olivine crystals with normal mantle δ 18 O composition suggests that depleted 18 O basaltic magmas in Iceland must result from assimilation of material that has undergone hydrothermal alteration by isotopically light meteoric fluids (Bindeman et al., 2008;Gurenko et al., 2015). Compositional differences in δ 18 O between zircon and the melt from which it grew (under equilibrium conditions) depend on factors such as melt composition and temperature. In a rhyolitic melt, zircon has δ 18 O ~ 1.8‰ lower than that of parent melt at 850°C (Bindeman et al., 2008;Trail et al., 2009). Crystallization progression can also affect melt δ 18 O. For example, extended closed-system crystallization of mafic melt leads to δ 18 O increase of ~0.5 to 1‰ in the rhyolite melt produced from such fractionation (e.g., Bindeman, 2008;Trail et al., 2009;cf. Valley et al., 2005). Over 90% of zircon δ 18 O values for analyzed Westfjords samples are between +2 and +4‰, which is within the typical range of δ 18 O for Icelandic zircons (Carley et al., 2014(Carley et al., , 2020)). The O isotope compositions of Westfjords zircon demonstrate that these grains crystallized from source melts with a variety of δ 18 O values, at least some of which likely included low-δ 18 O hydrothermally altered crust.
There are many petrogenetic pathways that may have led to the median value for HrE3 or ÁrE4 zircon of δ 18 O~3.3‰. For example, crystallization from a melt with a roughly 3:1 mixture of δ 18 O=5.5‰ melt and an assimilant with δ 18 O=2.0‰ may have been required (Supplemental Table S7). Alternatively, the observed isotopic signature could also be derived from-for example-crystallization of zircon from a 92:8 mixture of magma with δ 18 O=5.0‰ and an assimilant with δ 18 O=0.0‰. For the majority of potential mantle and assimilant values, anywhere from none to 50% assimilant is a viable option to produce the observed zircon δ 18 O values. Kaldalón samples have median δ 18 O=2.3‰ and 2.8‰. Most models (Supplemental Table S7) suggest higher assimilation manuscript submitted to Journal of Geophysical Research-Solid Earth amounts-likely ~30-60%-of low-18 O material is a required component in Kaldalón magmas in order to obtain the observed zircon values. However, major and trace element compositions (Supplemental Table S6) and zircon compositions (Supplemental Table S2)
of the silicic samples detailed here dictate that any assimilant to produce such parent magmas must be fairly silicic itself.
No single model can account for the range of observed zircon δ 18 O values given the uncertainty in source material and assimilant δ 18 O composition. Regardless, the majority of simple two-component mixing scenarios suggest that Hrafnsfjörður and Árnes zircon crystallized from melts with a minor low-18 O component, while Kaldalón zircon crystallized from melts with greater incorporation of a low-18 O component.
Relatively high intra-sample variabilities (Fig. 2) support protracted open-system or incomplete mixing conditions in most sampled locations, as do petrographic observations.
Two Hrafnsfjörður samples, KK-24 and HfE3, have more radiogenic whole rock εHf (~+14.5 and +15) than those samples' zircon weighted means (εHf~+15.6 and +16.0, respectively), while Árnes samples have less radiogenic Hf isotope compositions (whole rock εHf~+12.8 to 13.4; zircon weighted sample mean εHf~+12 to 13). The differences in Hf isotope composition between Hrafnsfjörður and Árnes-given their proximity-are intriguing, as are the differences between Hrafnsfjörður zircon and whole rock radiogenic Hf isotope compositions in samples KK24 and HfE3. Kaldalón samples lack whole rock isotopic data for further comparison. For these Hrafnsfjörður samples to have a Hf isotope composition >1 epsilon unit higher than the Árnes rhyolites, either (A)
Hrafnsfjörður magma was generated in a mantle region that was locally more depleted manuscript submitted to Journal of Geophysical Research-Solid Earth (more radiogenic) than the source of Árnes magma; or (B) Hrafnsfjörður magma incorporated pre-existing, more radiogenic material (e.g., older Icelandic bedrock or trapped oceanic crust, or melt derived therefrom). Furthermore, the difference between Hrafnsfjörður whole rock and zircon εHf requires hybridization, with zircon and whole rock reflecting more-and less-radiogenic magmas, respectively.
A rough but systematic northerly increase in Hf isotope ratios from ~N63°-66° in Iceland has been observed (Carley et al., 2020;cf. Peate et al., 2010;Harðardóttir et al., 2022). This general trend might suggest that regional variation in the underlying mantle (interpretation A above) accounts for the general difference in isotopic composition between the two volcanic centers. However, the observed trend is not strong enough to account for 1-2 epsilon units in only 15' latitude. Perhaps more extreme, local-scale heterogeneity is responsible, as is proposed by Harðardóttir et al. (2022). However, this hypothesis is difficult to test in these old rocks due to lack of preservation and exposure.
Thus, while we cannot rule out interpretation (A), the difference between Hrafnsfjörður whole rock and zircon εHf favors interpretation B (incorporation of underlying, more radiogenic material) as more likely to account for the observed differences between Árnes and Hrafnsfjörður εHf values.
Examination of differences in Hf isotope compositions between zircon grains and their host rocks provides insight into the potential for open-system magma evolution.
Hafnium is far more compatible in zircon than in other phases present in the Westfjords rocks. Therefore, almost all Hf not contained within zircon crystals is sequestered in the melt, and discrepancies between rock and zircon εHf strongly suggest that the zircon crystals grew in melt(s) with Hf isotope compositions that differ from those in which the manuscript submitted to Journal of Geophysical Research-Solid Earth crystals finally erupted. It is plausible that the Hrafnsfjörður samples comprised both the high εHf host magma that yielded the zircons (derived from more radiogenic crust?), and a less radiogenic component (magma from a mantle source similar to that of Árnes?).
These magmas would have mixed in varying proportions to yield hybrids with the observed εHf ~+14.5 and +15. This idea is supported by identification of a major shift in isotopic composition in the oldest rocks at an important 14.9 Ma unconformity in the Westfjords ( Hardarson et al., 1997). Rocks interpreted to have erupted from the Northwest Rift Zone (Fig. 1)-the precursor to the SSRZ-prior to 14.9 Ma have more radiogenic Nd isotope ratios than rocks younger than 14.9 Ma erupted from the SSRZ (Hardarson et al., 1997). Therefore, these earliest-erupted lavas from the NWRZ could source the more radiogenic Nd-Hf component required to form the Hrafnsfjörður silicic magmas, while being absent from Árnes due to their limited geographic extent.
The nature and origin of a high-εHf component implicated in process B above and in hybridization is enigmatic. Iceland's magmas are isotopically heterogeneous and hypothesized to result from mantle contributions with at least 3-4 compositional end member compositions (e.g., Sigmarsson et al., 1992;Hanan & Schilling, 1997;Hilton et al., 1999;Prestvik et al., 2001;Thirlwall et al., 2004;Kokfelt et al., 2006;Kitagawa et al., 2008). In addition to Hrafnsfjörður having a significantly more radiogenic Hf isotope composition than Árnes, Hrafnsfjörður also has slightly more radiogenic Nd and less radiogenic Pb isotope compositions than those observed at Árnes (Fig. 4). Hanan and Schilling (1997) attributed a correlation of higher extrusion rates of Tertiary (Miocene)
Westfjords lavas (some within several km of Árnes) with more radiogenic Pb compositions to a plume-entrained, radiogenic component. Kitagawa et al. (2008) note a manuscript submitted to Journal of Geophysical Research-Solid Earth similar correlation between isotopic compositions and extrusion rates in ~13-12 Ma basalts in eastern Iceland. Could variations in extrusion rates and plume contributionswhich are also tied to magma flux-be resolvable over the distance and time scales that separate Hrafnsfjörður and Árnes? 4.2.4 Geodynamic change: A role for variable spreading rates and/or magma flux?
The apparent age-distance discrepancy between Árnes, the SSRZ, and
Hrafnsfjörður could be explained by a higher spreading rate during the ~1 Myr between when Hrafnsfjörður and Árnes were active, followed by a reduced spreading rate for the remainder of the SSRZ's lifetime. The more radiogenic Pb compositions of Árnes samples (Fig. 4)-younger than Hrafnsfjörður samples (Fig. 2)-are also explained by this scenario.
The Icelandic mantle plume is hypothesized to pulse rather than maintain a steady magmatic flux (e.g., Kitagawa et al., 2008;O'Connor et al., 2000;White and Lovell, 1997;Jones et al., 2002;Hanan and Schilling, 1997). If the plume produced larger volumes of magma in conjunction with a higher half-spreading rate of ~3 cm/yr during Hrafnsfjörður and Árnes formation, a lateral separation distance of ~30 km would result.
This approximates their present-day separation distance. Initial, fast spreading must have been followed by a period of lower-than-average half-spreading at <0.5 cm/yr in order to yield modern crust-rift geometry-a pattern observed in Tertiary basalts at varying latitudes in Western and Eastern Iceland (Hanan & Schilling, 1997). A half-spreading rate of ~3 cm/yr is several times higher than the current ~1 cm/yr average half spreading rate of the modern rift zones in Iceland (Fig. 1 inset). Such a high spreading rate is manuscript submitted to Journal of Geophysical Research-Solid Earth unusual for Iceland, as are major variations in spreading rate (e.g., Martin et al., 2011).
However, hypotheses about variable spreading rates have a precedent-Garcia et al.
(2003) invoked a similar rate in their model of northern Iceland evolution. Further, it is plausible that rifting rates are variable over timescales of <1 Myr in Iceland and that such variations may be difficult to discern in the geologic record without the multifaceted (coupled zircon age/isotope/whole rock/mapping) perspective employed in this study.
Due to uncertainty in the location of the SSRZ rift axis, it may be also possible that Árnes was located further from the rift axis when it was an active system than was
Hrafnsfjörður. This would have allowed for melt extraction at greater mantle depths, thereby reducing the likelihood of contamination by shallow melts and increasing the radiogenic components in Árnes magmas as we observe (Stracke & Bourdon, 2009).
The SSRZ began to share magmatic output with the propagating Northern rift zone (NRZ; Fig. 1) around 13 Ma (Martin et al., 2011), and overall magma flux (and potentially spreading rate) at the SSRZ likely diminished over its waning years. A similar pattern of output waning at one rift while magma flux increases at another is currently proposed for the active-but-diminishing WVZ and propagating EVZ (e.g., Jordan et al., 2019;Sinton et al., 2005). Temporal variation in magma flux has been proposed to result from rift relocation, with magma flux generally decreasing over time (Hardarson et al., 1997). However, analysis of the prominent pattern of gravity anomalies in the sea floor around Iceland (Reykjanes V-shaped ridges) suggests that they result from plume pulsing, and that rift relocation had little to no effect on plume upwelling (Ito, 2001;Jones et al., 2002;cf. Hey et al., 2010;Martinez & Hey, 2017). Therefore, it appears that while invoking changes in magma flux may explain part of the temporal issue elucidated manuscript submitted to Journal of Geophysical Research-Solid Earth by the zircon ages, it does little to explain the observed Hf, Nd, and Pb isotopic differences observed between Hrafnsfjörður and Árnes. These differences are better accommodated by invoking either a pulsing mantle plume scenario; heterogeneity in the underlying mantle (e.g., Harðardóttir et al., 2022); differences in melting depth due to variable distances from the rift axis (Stracke & Bourdon, 2009); or some combination of these factors.
The Icelandic hot spot is a manifestation of a mantle plume that originates at depths of at least 400 km (Wolfe et al., 1997), and likely into the lower mantle (He et al., 2015;Shen et al., 1998). In the >60 Myr that the Iceland plume has been active, numerous iterations of pulses-thermal, volumetric, and chemical-have been documented. Seismic and geochemical analyses of exposed paleo-landscapes suggest thermal pulsing of the Icelandic mantle plume began early in its existence (Parnell-Turner et al., 2014, 2017;Spice et al., 2016;Stucky de Quay et al., 2017). Geochronological analysis of Iceland plume eruptive products elsewhere in the North Atlantic suggests plume pulses on timescales of 5-10 Myr (O'Connor et al., 2000). Rocks that largely span Iceland's subaerial existence exhibit distinct, time-dependent variations in accumulation rate, isotopic signature, and elemental composition, with pulses ~6-7 Myr apart (Hanan & Schilling, 1997;Kitagawa et al., 2008;Thirlwall et al., 2004). The ages and compositions observed at Hrafnsfjörður and Árnes align well with these trends (Fig. 6). Iceland mantle plume pulsing is likely correlated with bulk compositional differences in material entrained in the plume (Hanan & Schilling, 1997;Kitagawa et al., 2008), although thermal perturbations must also be considered (e.g., Parnell-Turner et al., 2017;Spice et al., 2016). In their studies of Tertiary (Miocene) lava compositions from Iceland's eastern and northwestern margins, Hanan and Schilling (1997), Thirlwall et al. (2004), andKitagawa et al. (2008) identify at least two isotopically enriched (i.e., high amounts of radiogenic Pb vs. non-radiogenic Pb, low amounts of radiogenic Hf and Nd vs. non-radiogenic Hf and Nd) endmember components that-along with at least one depleted end-member component-dominate the Iceland plume (Fig. 4c). Source regions manuscript submitted to Journal of Geophysical Research-Solid Earth with a higher proportion of the enriched components are more easily melted than those with a higher proportion of the depleted component. Therefore, melting of mantle with larger proportions of the enriched components should yield greater magma production at a given temperature (Kitagawa et al., 2008), leading to increases in magma flux and eruption rate. This pattern has been convincingly demonstrated in the basalt succession of eastern Iceland from 13-2 Ma (Hanan & Schilling, 1997;Kitagawa et al., 2008) and western Iceland from 13-8 Ma (Hanan & Schilling, 1997).
Our new data from Árnes (~13 Ma) and Hrafnsfjörður (~14 Ma) extend the previously observed geochemical trends in western Iceland. These volcanic centers have Pb isotope ratios that are consistent with the proposed time-integrated trends of a pulsing plume (Hanan & Schilling, 1997;Kitagawa et al., 2008). Hafnium and Nd isotope compositions become less radiogenic over time, as is observed in rocks from eastern Iceland during the same time interval. Hrafnsfjörður zircon Hf isotope compositions indicate crystallization from a source magma with a more radiogenic composition than required for Árnes magmas, which suggests involvement of more 176 Hf-enriched crust in their genesis. Oxygen isotope compositions in zircons from Hrafnsfjörður, Kaldalón, and Árnes also support the involvement of pre-existing altered crustal material in zircon source magmas. Petrogenesis of these Westfjords magmas is best considered within the context of the model proposed by Kitagawa et al. (2008), albeit starting earlier than the 13 Myr originally considered by those authors. Zircon U-Pb ages from Hrafnsfjörður and Kaldalón indicate the formation of silicic material-and the establishment of central manuscript submitted to Journal of Geophysical Research-Solid Earth volcanic complexes-by at least 14.3 Ma. Differences in O isotope compositions in zircon grains indicate that silicic magmas at Kaldalón incorporated a larger proportion of low-18 O crustal material compared to those from Hrafnsfjörður, which formed roughly contemporaneously ~15 km to the northwest. These data suggest that the Kaldalón rhyolites incorporated a larger proportion of pre-existing crust than rhyolites from Árnes or Hrafnsfjörður. Our data support the presence of a mantle source with Pb isotope
compositions that become more radiogenic and Hf and Nd isotope compositions that become less radiogenic with decreasing age (Fig. 7). We interpret this trend to reflect the increasing dominance of an enriched-composition plume pulse over the period from ~14 to 13 Ma. This pulse is likely to have also coincided with greater mantle melting and melt flux to the surface, potentially leading to a temporary increase in spreading rate.
Estimates of establishment rates of rhyolite-producing central volcanoes at rifts that are ~1-2 Myr old, as was the case with the SSRZ at the time these systems were active, suggest that it takes several 100s of kyr to develop the crustal infrastructure to produce silicic magmas (Banik et al., 2018). Our geochronology results in the northern Westfjords support that interpretation. Árnes zircon ages establish the formation of an edifice by at A constant spreading rate is not fully suited to explain the geodynamic development of the northern Westfjords. Discrepancies in distances between (1) Árnes and Hrafnsfjörður and (2) Árnes and the SSRZ preclude such a simple paradigm. Instead, Iceland's geodynamic evolution.
• Ages from three of the oldest dated central volcanoes in Iceland indicate lifespans of silicic volcanism of ~500 kyr for each system. Árnes rhyolites yield weighted mean ages from 12.8±0.1 to 13.1±0.4 Ma (2SE); Kaldalón rhyolites range from 13.6±0.5 to 14.1±0.6 Ma. Hrafnsfjörður dacites-including the oldest silicic unit dated in Iceland-have weighted mean ages from 13.7±0.2 to 14.3±0.1 Ma (2σ SE). These ranges are on the short end of typical Icelandic central volcano lifespans, but do not include associated basalts and therefore these systems were likely longer-lived.
• Geodynamic evolution of the Westfjords is not straightforward, as demonstrated by the apparent mismatch in ages of Árnes and Hrafnsfjörður and distances between those volcanoes and the SSRZ from which they erupted.
• Hrafnsfjörður, Árnes, and especially Kaldalón silicic rocks have zircon with isotopically light d 18 O, as is ubiquitous for on-rift-produced systems in Iceland, indicating the influence of hydrothermally altered crust in melts prior to zircon crystallization. manuscript submitted to Journal of Geophysical Research-Solid Earth • Hrafnsfjörður rocks are less radiogenic in Pb, but more radiogenic in Nd and Hf, than those from Árnes, potentially resulting from a pulse of plume-derived, enriched magma. These data provide (1) support for possible variability of rifting rates and magma flux in Iceland's past, and (2) further age-correlated characterization of the heterogeneous mantle plume under Iceland. Original data from this research are archived at EarthChem [DOI: 10.26022/IEDA/112925]. Data used for Iceland zircon comparisons are available in Carley et al. (2014, 2020) and Banik et al. (2018, 2021). Iceland whole rock isotope data compilation available in Harðardóttir et al. (2022). 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DOI: 10.1038/s41467-022-31348-7 Bindeman, Ilya, Gurenko, A., Sigmarsson, O., & Chaussidon, M. (2008). Oxygen isotope heterogeneity and disequilibria of olivine crystals in large volume Holocene basalts from Iceland: Evidence for magmatic digestion and erosion of Pleistocene hyaloclastites. Geochimica et Cosmochimica Acta, 72(17), 4397-4420. DOI: 10.1016/J.GCA.2008.06.010 Bindeman, Ilya, Gurenko, A., Carley, T., Miller, C., Martin, E., & Sigmarsson, O. (2012). Silicic magma petrogenesis in Iceland by remelting of hydrothermally altered crust based on oxygen isotope diversity and disequilibria between zircon and magma with implications for MORB. Terra Nova, 24(3), 227-232. DOI: 10.1111/j.1365-manuscript submitted to Journal of Geophysical Research-Solid Earth Saemundsson, K. (1974). Evolution of the Axial Rifting Zone in Northern Iceland and the Tjörnes Fracture Zone. GSA Bulletin, 85(4), 495-504. DOI: 10.1130/0016-7606(1974)85<495:EOTARZ>2.0.CO;2 Saemundsson, K. (1979). 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DOI: 10.1130/0091-7613(1991)019<0621:OOSMII>2.3.CO;2 Sigmarsson, O., Condomines, M., & Fourcade, S. (1992a). A detailed Th, Sr and O isotope study of Hekla: differentiation processes in an Icelandic volcano. Contributions to Mineralogy and Petrology, 112, 20-34. DOI: 10.1007/BF00310953 Sigmarsson, O., Condomines, M., & Fourcade, S. (1992b). Mantle and crustal contribution in the genesis of Recent basalts from off-rift zones in Iceland: manuscript submitted to Journal of Geophysical Research-Solid Earth SSRZ N W R Z 66˚N 65˚N 66˚N 65˚N 24˚W 22˚W 20˚W 23˚W 21˚W 19˚W x2 x3 1 3 2 a b c d e f 4 5 g Árnes Hrafnsfjörður Kaldalón Kaldalón 50 km Central volcano (approx.) Sample Drangajökull (glacier) Legend DH04 DH08 DH15 (a) (b) (c) U-Pb Age (Ma) zircon δ 18 O (‰) zircon ε Hf KK-24 KlE1 HfE3 HfE2 KlE2 ÁrE1 DH ÁrE3 ÁrE4 KK-24 KlE1 HfE3 HfE2 KlE2 ÁrE1 DH ÁrE3 ÁrE4 KK-24 DH ÁrE3 ÁrE4 ÁrE1 KlE1 HfE3 HfE2 KlE2 Avg. mantle zircon δ 18 O=5.3±0.6‰ (2σ) (Valley, 2003) -2 -1 0 1 2 3 4 5 6 * ********** ********** ********* ********** **** Age (Ma) MSWD 14.3± 0.1 0.7 14.1±0.4 13.9±0.2 13.7± 0.2 13.6± 0.5 13.1± 0.4 13.1± 0.3 12.8± 0.4 12.8±0.1 1.3 4.1 1.7 2.5 1.1 2.7 3.1 1.1 4.0±0.09 2.2±0.12 3.5±0.08 3.5± 0.2 3.5±0.08 3.4± 0.16 3.1±0.05 3.3±0.08 2.9± 0.13 δ 18 O (‰) ε Hf MSWD 15.6±0.4 1.2 12.7±0.4 ---11.8± 0.9 13.0±0.5 0.5 ---1.5 1.6 15.5±0.5 0.3 16.0±0.5 0.5 15.3± 0.7 0.6 14.8± 0.6 0.3 ~800˚C ~850˚C ~900˚C ~950˚C ~750˚C Hrafnsfjörður Kaldalón 10 12 14 16 18 Age (Ma) 1 10 100 Yb/Gd 6,000 11,000 16,000 Hf (ppm) 18.0 18.5 19.0 19.5 206 Pb/ 204 Pb 18.0 18.5 19.0 19.5 ε Hf ε Nd 65.5°66°66.5°6 5.5°N 66°N 24°W 22°W 20°W 24°W 22°W 20°W ~40 km ~46 km ~67 km ~78 km ~31 km Spreading 30° oblique to SSRZ axis Spreading perpendicular to SSRZ axis Spreading 30° oblique to SSRZ axis Spreading perpendicular to SSRZ axis To Árnes: To Hrafnsfjörður: Hrafnsfjörður Árnes Gláma Projected SSRZ axis (Harðarson et al., 2008) Approximate extent of central volcano East Iceland Kitagawa et al., 2008 Hanan & Schilling, 1997 This Study Árnes Hrafnsfjörður West Iceland Vestfirðir; Hanan & Schilling, 1997 Strandir; Hanan & Schilling, 1997 Súgandafj.; Hardarson et al., 1997 1 8 . 0 1 8 . 2 1 8 . 4 1 8 . 6 1 8 . 8 1 9 . 0 1 9 . 2 Age (Ma) 206 Pb/ 204 Pb A HK ε Hf ε Nd Rad. Pb 'EM'-like component Spreading rate Hrafnsfj. Kaldalón Árnes ~14 Ma H K B ~13.5 Ma NW SE C ~13.0 Ma Á HKÁ D ~12.5 Ma H K Á SSRZ More radiogenic Less radiogenic Higher δ 18 O/More FC of NMI Lower δ 18 O/More PM of PEC H Á K Table 1. Summary of Westfjords samples Volcano Sample name Fig. S1 Unit Rock type Árnes ÁrE1 Tr4 rhyolite Árnes ÁrE2 Tr1? Ta? bas-andesite Árnes ÁrE3 Tr2 rhyolite Árnes ÁrE4 Tr3 rhyolite Árnes ÁrE5 Tr3 rhyolite Árnes ÁrE6 Tis dacite Árnes DH-04 Tr1 rhyolite Árnes DH-08 Tr1 rhyolite Árnes DH-15 Tr1 rhyolite Hrafnsfjörður KK-24 Tdh dacite Hrafnsfjörður HfE1 Tad bas-andesite Hrafnsfjörður HfE2 Tdb dacite Hrafnsfjörður HfE3 --andesite Kaldalón KlE1 --rhyolite Kaldalón KlE2 --rhyolite Description zrc? Fresh with minor flow bands Y Moderate alteration, platey Y Major flow bands, platey, pervasive alteration Y Platey and maybe altered; white dome top Y Black and vitreous, but altered N Black and vitreous, aphyric, columnar, fresh N Med. gray and porphyritic, with plag and CPx phenos Y Med.-dark gray and porphyritic, with plag and CPx phenos Y Med.-light gray, some altn, porphyritic, with plag and CPx phenos Y Dark ray aphyric, fresh Y Aphanitic, black, fresh with weathering veneer N Aphanitic, black, fresh with weathering veneer Y Minor flow bands, weathered surface, grey and aphyric Y Dark grey with faint flow bands; vitrophyric g'mass Y Slight purple tint w/ sparse plag phenos and aphanitic g'mass Y Sample n of N Age (Ma) 2 SE MSWD n of N δ 18 O (‰) 2 SE Median n of N ε Hf 2 SE KK-24* 14 of 14 14.3 0.1 0.7 12 of 12 3.4 0.4 3.0 of 14 15.6 0.4 HfE2 10 of 10 13.7 0.2 1.1 6 of 6 3.5 0.5 3.7 of 3 15.3 0.7 HfE3 23 of 24 13.9 0.2 2.7 18 of 19 3.5 0.2 2.3 of 7 16.0 0.5 KlE1 12 of 13 14.1 0.4 3.1 12 of 14 2.1 0.2 3.3 of 5 15.5 0.5 KlE2 10 of 10 13.6 0.5 2.5 10 of 10 2.9 0.4 2.8 of 4 14.8 0.6 ÁrE1 8 of 8 13.1 0.3 4.1 9 of 10 3.4 0.1 3.4 of 1 12.4 1.7** ÁrE3 10 of 10 13.1 0.4 1.7 24 of 24 3.5 0.1 3.6 of 15 12.7 0.4 ÁrE4 23 of 24 12.8 0.1 1.1 23 of 23 3.3 0.2 3.3 of 15 13.0 0.5 DH-04 ----------------of 3 11.8 0.9 DH-08 ------DH-15 ------**Uncertainty is 2SD since only one grain was analyzed U-Pb geochronology Oxygen isotopes Hafnium isotopes Hrafnsfjörður Kaldalón Árnes 8 of 8 12.8 0.4 1.1 16 of 17 3.1 0.2 3.0 *O and Hf isotope data from Carley et al. (2020). Age from Jordan et al. (2013) and Carley et al. (2020).
Hafnium isotopes 020). Age from Jordan et al. (2013) and Carley et al. (2020).
Table S1. In situ U-Pb zircon geochronology RED not included in Mean age either b/c considered faulty or from a different age population; Errors are 1σ unless otherwise noted. Ages are 230 Th-corrected. Analysis Mount Date 207 Pb & 230 Th-corr. 206 Pb / 238 U Age (Ma) 1σ err Th (ppm) U (ppm) 204 Pb / 206 Pb % err 207 Pb / 206 Pb % err 208 Pb / 206 Pb % err 207 Pb-corr 204 Pb / 206 Pb Árnes: ÁrE1301 (aka ÁrE1) (Tr4 rhyolite) ArE1301-1.1 TJB.07 Apr-14 11.60 0.35 70 118 8.67E-03 77 0.067 11 0.382 1.41E-03 ArE1301-2.1 TJB.07 Apr-14 13.10 0.38 39 73 1.66E-03 183 0.078 15 0.297 2.13E-03 ArE1301-3.1 TJB.07 Apr-14 13.91 0.32 69 122 -1.86E-03 105 0.095 12 0.441 3.30E-03 ArE1301-4.1 TJB.07 Apr-14 12.77 0.36 91 152 1.50E-02 54 0.070 11 0.248 1.62E-03 ArE1301-5.1 TJB.07 Apr-14 12.00 0.47 101 172 4.11E-03 100 0.069 9 0.274 1.51E-03 ArE1301-6.1 TJB.07 Apr-14 13.71 0.47 66 114 2.35E-02 54 0.089 13 0.407 2.92E-03 ArE1301-7.1 TJB.07 Apr-14 13.44 0.36 117 155 9.28E-04 183 0.057 19 0.211 7.56E-04 ArE1301_18-6.1 TJB.18 Jan-19 13.33 0.60 27 61 5.4E-2 40 0.08 14 0.30 0.002 Mean age of coherent group (N=8) 12.99 Probability 0.00 Age error (95% conf., with error in Std) 0.71 MSWD 4.7 Árnes: ÁrE1303 (aka ÁrE3) (Tr2 rhyolite) ArE1303-10.1 TJB.06 Apr-14 12.82 0.50 60 110 4.50E-03 112 0.056 16 0.179 6.27E-04 ArE1303-12.1 TJB.06 Apr-14 12.89 0.32 58 94 -9.06E-03 91 0.042 19 0.444 -2.74E-04 ArE1303-2.1 TJB.06 Apr-14 14.07 0.41 65 99 8.54E-03 91 0.049 20 0.208 1.66E-04 ArE1303-25.1 TJB.06 Apr-14 13.13 0.49 54 88 1.43E-02 75 0.046 19 0.357 -5.98E-06 ArE1303-26.1 TJB.06 Apr-14 13.02 0.36 115 173 -3.32E-03 112 0.030 20 0.179 -1.10E-03 ArE1303-27.1 TJB.06 Apr-14 13.74 0.32 679 711 -6.90E-04 129 0.051 7 0.254 3.03E-04 ArE1303-3.1 TJB.06 Apr-14 12.74 0.51 62 94 8.97E-03 100 0.071 17 0.188 1.66E-03 ArE1303-7.1 TJB.06 Apr-14 13.04 0.77 50 85 1.80E-03 224 0.061 19 0.101 9.90E-04 ArE1303-8.1 TJB.06 Apr-14 12.43 0.40 172 215 1.50E-03 158 0.044 14 0.167 -1.40E-04 ArE1303-9.1 TJB.06 Apr-14 12.76 0.30 54 96 3.24E-03 158 0.050 18 0.189 2.27E-04 Mean age of coherent group (N=10) 13.09 Probability 0.09 Age error (95% conf., with error in Std) 0.37 MSWD 1.7 Árnes: ÁrE1304 (aka ÁrE4) (Tr3 rhyolite) ArE1304-1.1 TJB.07 Apr-14 13.10 0.19 111 183 4.40E-03 120 0.040 12 0.161 -4.42E-04 ArE1304-10.1 TJB.07 Apr-14 12.86 0.40 86 147 1.42E-02 50 0.080 17 0.280 2.30E-03 ArE1304-11.1 TJB.07 Apr-14 12.60 0.17 74 114 1.25E-02 71 0.065 12 0.241 1.26E-03 ArE1304-12.1 TJB.07 Apr-14 12.97 0.20 182 256 4.97E-03 77 0.041 10 0.246 -3.67E-04 ArE1304-13.1 TJB.07 Apr-14 12.67 0.19 154 192 2.99E-03 100 0.049 11 0.325 1.73E-04 ArE1304-14.1 TJB.07 Apr-14 12.55 0.44 48 100 2.34E-03 129 0.046 16 0.082 -3.66E-05 ArE1304-15.1 TJB.07 Apr-14 12.80 0.33 79 141 6.97E-03 100 0.045 14 0.199 -1.08E-04 ArE1304-16.1 TJB.07 Apr-14 12.57 0.24 83 143 6.52E-03 100 0.046 12 0.187 -3.79E-05 ArE1304-2.1 TJB.07 Apr-14 13.27 0.21 155 239 1.58E-03 183 0.044 10 0.201 -1.53E-04 ArE1304-3.1 TJB.07 Apr-14 12.92 0.15 284 367 1.49E-03 316 0.055 7 0.261 6.13E-04 ArE1304-4.1 TJB.07 Apr-14 12.65 0.38 105 179 2.92E-03 100 0.046 11 0.342 17 -8.63E-06 ArE1304-5.1 TJB.07 Apr-14 13.04 0.21 140 192 4.55E-03 100 0.045 10 0.270 18 -6.42E-05 ArE1304-6.1 TJB.07 Apr-14 13.25 0.45 40 74 1.06E-02 120 0.046 17 0.140 36 -5.46E-06 ArE1304-7.1 TJB.07 Apr-14 12.60 0.59 27 79 1.29E-02 100 0.050 17 0.111 41 2.56E-04 ArE1304-8.1 TJB.07 Apr-14 13.09 0.18 100 162 5.56E-03 100 0.038 12 0.183 21 -5.77E-04 ArE1304-9.1 TJB.07 Apr-14 13.20 0.31 194 281 3.35E-03 100 0.044 9 0.201 16 -1.49E-04 ArE1304F-1.1 TJB.08 Apr-14 12.76 0.18 633 701 2.15E-03 75 0.049 6 0.300 9 2.09E-04 ArE1304F-2.1 TJB.08 Apr-14 12.56 0.14 354 340 6.84E-04 129 0.042 18 0.330 12 -3.05E-04 ArE1304F-3.1 TJB.08 Apr-14 12.64 0.26 219 280 2.98E-03 120 0.049 9 0.281 15 1.96E-04 ArE1304F-4.1 TJB.08 Apr-14 12.72 0.18 311 374 2.58E-03 120 0.041 9 0.172 17 -3.58E-04 ArE1304F-5.1 TJB.08 Apr-14 12.61 0.27 355 375 6.23E-03 50 0.043 8 0.263 12 -2.38E-04 ArE1304F-6.1 TJB.08 Apr-14 12.87 0.22 550 565 3.69E-04 129 0.043 6 0.264 10 -2.14E-04 ArE1304F-7.1 TJB.08 Apr-14 13.10 0.26 167 268 1.80E-03 100 0.052 18 0.239 15 4.05E-04 Mean age of coherent group (N=23) 12.84 Probability 0.36 Age error (95% conf., with error in Std) 0.09 MSWD 1.08 Árnes: DH-04, DH-08, and -15 (Tr1 rhyolite) DH04-3.1 TJB.10 Oct-14 14.02 1.51 147 198 1.74E-03 71 0.064 9 0.284 8 1.20E-03 DH04-8.1 TJB.10 Oct-14 12.43 0.41 173 218 3.90E-03 41 0.057 9 0.336 7 7.41E-04 DH04-10.1 TJB.10 Oct-14 6.90 2.24 128 122 9.02E-03 41 0.153 15 0.570 9 7.21E-03 DH08-1.1 TJB.09 Apr-14 12.82 0.91 45 80 -1.19E-02 100 0.035 26 0.166 46 -7.80E-04 DH08-2.1 TJB.09 Apr-14 12.69 0.40 102 128 -1.83E-03 224 0.057 18 0.236 34 7.07E-04 DH08-4.1 TJB.09 Apr-14 11.65 0.70 16 39 5.10E-03 224 0.082 25 0.362 46 2.39E-03 DH08-5.1 TJB.09 Apr-14 13.45 0.50 73 119 -1.35E-03 224 0.069 16 0.391 23 1.56E-03 DH08-7.1 TJB.09 Apr-14 13.11 0.51 139 192 4.97E-03 91 0.164 8 0.537 16 7.94E-03 DH15-13.1 TJB.09 Apr-14 16.40 2.80 620 618 5.82E-03 53 0.237 21 0.713 16 1.29E-02 DH15-12.1 TJB.09 Apr-14 11.88 0.63 68 101 3.27E-03 158 0.074 17 0.314 28 1.87E-03 DH15-3.1 TJB.09 Apr-14 13.28 0.37 89 126 2.65E-02 51 0.082 14 0.472 21 2.43E-03 Mean age of coherent group (N=10) 12.82 Probability 0.23 Age error (95% conf., with error in Std) 0.44 MSWD 1.3 Hrafnfjörður: HfE1402 (aka HfE2) (Tdb dacite) HfE1402-1.1 TJB.11 Oct. 2014 13.77 0.21 161 206 1.58E-03 71 0.049 10 0.294 8 2.08E-04 HfE1402-10.1 TJB.11 Oct. 2014 13.72 0.27 29 55 1.00E-32 100 0.083 16 0.282 15 2.49E-03 HfE1402-11.1 TJB.11 Oct. 2014 13.72 0.34 176 153 -4.39E-03 50 0.061 11 0.380 9 9.81E-04 HfE1402-2.1 TJB.11 Oct. 2014 13.92 0.31 140 409 1.00E-32 100 0.054 7 0.109 9 5.17E-04 HfE1402-3.1 TJB.11 Oct. 2014 13.92 0.23 339 393 2.41E-03 41 0.056 7 0.322 5 6.65E-04 HfE1402-4.1 TJB.11 Oct. 2014 13.69 0.65 55 66 -2.28E-03 100 0.059 16 0.382 12 8.61E-04 HfE1402-5.1 TJB.11 Oct. 2014 13.49 0.33 255 368 9.25E-04 71 0.049 8 0.264 6 1.50E-04 HfE1402-6.1 TJB.11 Oct. 2014 11.97 0.85 86 150 5.22E-03 45 0.068 9 0.275 9 1.48E-03 HfE1402-7.1 TJB.11 Oct. 2014 13.81 0.34 352 388 2.78E-03 45 0.093 11 0.350 6 3.17E-03 HfE1402-8.1 TJB.11 Oct. 2014 14.34 0.49 10 35 8.46E-03 71 0.086 17 0.356 17 2.68E-03 HfE1402-9.1 TJB.11 Oct. 2014 13.49 0.11 374 315 -5.60E-04 100 0.053 8 0.396 6 4.73E-04 Mean age of coherent group (N=10) 13.65 Probability 0.36 Age error (95% conf., with error in Std) 0.15 MSWD 1.10 Hrafnfjörður: HfE1403 (aka HfE3) HfE1403-1.1 TJB.11 Oct. 2014 13.65 0.33 195 577 3.39E-03 30 0.059 12 0.138 7 8.80E-04 HfE1403-10.1 TJB.11 Oct. 2014 13.45 0.47 807 824 1.13E-03 41 0.051 5 0.338 4 3.04E-04 HfE1403-11.1 TJB.11 Oct. 2014 14.08 0.22 701 722 -2.55E-04 100 0.053 5 0.334 4 4.20E-04 HfE1403-12.1 TJB.11 Oct. 2014 13.47 0.45 109 171 2.27E-03 71 0.055 19 0.222 11 6.11E-04 HfE1403-13.1 TJB.11 Oct. 2014 13.12 0.48 138 248 9.59E-03 25 0.091 7 0.272 13 3.02E-03 HfE1403-14.1 TJB.11 Oct. 2014 13.06 0.29 188 271 1.26E-03 71 0.063 8 0.266 7 1.14E-03 HfE1403-15.1 TJB.11 Oct. 2014 13.36 0.47 500 1559 2.16E-04 71 0.047 4 0.111 5 4.30E-05 HfE1403-16.1 TJB.11 Oct. 2014 13.65 0.46 182 377 -4.09E-04 100 0.057 7 0.197 7 7.33E-04 HfE1403-17.1 TJB.11 Oct. 2014 13.90 0.49 91 200 2.72E-03 58 0.052 11 0.164 12 3.74E-04 HfE1403-18.1 TJB.11 Oct. 2014 14.41 0.11 243 386 1.79E-03 45 0.057 6 0.232 6 7.48E-04 HfE1403-19.1 TJB.11 Oct. 2014 13.09 0.28 321 888 9.97E-04 41 0.059 4 0.141 11 8.57E-04 HfE1403-2.1 TJB.11 Oct. 2014 13.53 0.43 727 1290 3.30E-04 58 0.058 3 0.194 4 7.59E-04 HfE1403-20.1 TJB.11 Oct. 2014 13.71 0.25 735 933 1.06E-03 35 0.051 4 0.300 3 3.23E-04 HfE1403-21.1 TJB.11 Oct. 2014 16.39 1.90 354 460 3.67E-03 30 0.062 6 0.332 5 1.04E-03 HfE1403-22.1 TJB.11 Oct. 2014 10.06 1.53 367 762 2.12E-03 25 0.054 4 0.196 4 5.55E-04 HfE1403-23.1 TJB.11 Oct. 2014 14.31 0.31 528 1344 4.83E-04 45 0.044 4 0.136 6 -1.28E-04 HfE1403-24.1 TJB.11 Oct. 2014 14.29 0.62 528 1707 8.07E-04 32 0.050 3 0.117 4 2.74E-04 HfE1403-3.1 TJB.11 Oct. 2014 14.00 0.33 41 84 4.00E-19 9999 0.097 11 0.349 11 3.41E-03 HfE1403-4.1 TJB.11 Oct. 2014 12.65 0.65 151 563 1.02E-03 50 0.056 5 0.130 7 6.29E-04 HfE1403-5.1 TJB.11 Oct. 2014 13.77 0.37 558 489 2.09E-03 38 0.046 6 0.361 4 1.02E-06 HfE1403-6.1 TJB.11 Oct. 2014 13.01 0.55 711 1842 7.50E-04 33 0.052 3 0.142 4 3.78E-04 HfE1403-7.1 TJB.11 Oct. 2014 13.45 0.62 1611 1542 4.85E-04 41 0.048 3 0.354 2 8.72E-05 HfE1403-8.1 TJB.11 Oct. 2014 14.02 0.28 297 489 2.89E-03 33 0.052 6 0.219 6 4.04E-04 HfE1403-9.1 TJB.11 Oct. 2014 13.47 0.38 445 1454 4.17E-04 50 0.049 4 0.115 5 2.01E-04 Mean age of coherent group (N=23) 13.93 Probability 0.00 Age error (95% conf., with error in Std) 0.22 MSWD 2.7 Kaldalón: KlE1401 (aka KlE1) KlE1401-2.1 TJB.11 Oct. 2014 10.11 1.73 253 237 -2.3E-3 127 0.056 10 0.339 14.8 0.00064 KlE1401-9.1 TJB.11 Oct. 2014 12.81 0.60 110 71 2.7E-3 242 0.066 13 0.251 13.1 0.00135 KlE1401-4.1 TJB.11 Oct. 2014 12.87 0.60 65 24 -1.4E-3 741 0.085 16 0.285 15.4 0.00263 KlE1401-10.1 TJB.11 Oct. 2014 13.22 0.44 76 37 -7.9E-3 104 0.073 15 0.412 11.3 0.00178 KlE1401-13.1 TJB.11 Oct. 2014 13.54 0.24 55 22 1.1E-2 90 0.078 14 0.382 12.4 0.00216 KlE1401-1.1 TJB.11 Oct. 2014 13.89 0.32 69 42 4.4E-3 171 0.154 9 0.608 13.6 0.00733 KlE1401-7.1 TJB.11 Oct. 2014 14.55 0.17 494 415 -4.1E-3 203 0.053 19 0.382 12.8 0.00047 KlE1401-6.1 TJB.11 Oct. 2014 14.59 0.41 46 18 2.5E-3 59 0.048 7 0.320 9.6 0.00015 KlE1401-11.1 TJB.11 Oct. 2014 14.64 2.03 111 69 2.0E-3 259 0.081 10 0.427 8.7 0.00238 KlE1401-3.1 TJB.11 Oct. 2014 14.71 0.85 89 56 5.0E-3 152 0.117 11 0.389 10.9 0.00479 KlE1401-5.1 TJB.11 Oct. 2014 14.89 0.70 48 16 4.4E-2 36 0.229 9 0.592 10.9 0.01239 KlE1401-8.1 TJB.11 Oct. 2014 15.04 0.90 62 28 6.7E-3 141 0.067 16 0.299 14.6 0.00143 KlE1401-12.1 TJB.11 Oct. 2014 17.07 1.48 55 25 1.3E-3 766 0.076 15 0.419 12.7 0.00201 Mean age of coherent group (N=13) 14.09 Probability 0 Age error (95% conf., with error in Std) 0.43 MSWD 3.1 Kaldalón: KlE1402 (aka KlE2) KlE1402-6.1 TJB.11 Oct. 2014 11.95 0.78 49 16 1.9E-3 669 0.100 16 0.360 15.1 0.00361 KlE1402-4.1 TJB.11 Oct. 2014 12.36 2.45 1312 1933 5.9E-4 97 0.055 11 0.549 11.3 0.00056 KlE1402-8.1 TJB.11 Oct. 2014 12.66 1.18 74 39 1.4E-2 79 0.151 11 0.718 11.0 0.00706 KlE1402-3.1 TJB.11 Oct. 2014 12.65 0.69 58 26 6.4E-3 162 0.095 14 0.302 14.5 0.00332 KlE1402-5.1 TJB.11 Oct. 2014 12.77 0.68 1215 1751 3.9E-4 141 0.057 4 0.624 5.0 0.00073 KlE1402-7.1 TJB.11 Oct. 2014 13.22 0.98 70 35 -9.6E-3 89 0.097 12 0.385 11.8 0.00341 KlE1402-2.1 TJB.11 Oct. 2014 13.42 0.21 217 133 3.5E-3 90 0.071 8 0.289 8.0 0.00166 KlE1402-1.1 TJB.11 Oct. 2014 13.80 0.78 32 13 -2.1E-3 603 0.105 17 0.381 16.1 0.00395 KlE1402-9.1 TJB.11 Oct. 2014 14.67 0.32 40 15 1.6E-2 85 0.079 18 0.328 15.8 0.00220 KlE1402-10.1 TJB.11 Oct. 2014 14.81 1.22 91 55 -8.8E-4 675 0.076 13 0.223 13.7 0.00201 Mean age of coherent group (N=10) 13.59 Probability 0.008 Age error (95% conf., with error in Std) 0.54 MSWD 2.5 207 Pb-corr % com 206 Pb UO/U % err 232 Th / 238 U % err Total 238 U / 206 Pb % err Total 207 Pb / 206 Pb % err 204 Pb-corr 207 Pb*/ 235 U % err 204 Pb-corr 206 Pb*/ 238 U % err err corr 2.63 4.99 0.80 0.61 0.26 545 2.9 0.067 11 0.0173 25 1.54E-03 15 0.6 3.98 5.05 1.29 0.55 0.42 475 2.5 0.078 15 0.0150 89 2.04E-03 6 0.1 6.16 4.59 2.10 0.58 1.00 437 1.8 0.095 12 0.0391 23 2.37E-03 4 0.2 3.03 4.84 2.21 0.62 2.23 493 2.7 0.070 11 0.0459 56 1.46E-03 21 0.4 2.82 5.06 1.27 0.60 0.64 526 3.9 0.069 9 0.0011 1477 1.76E-03 9 0.0 5.45 4.53 2.17 0.59 1.69 447 3.1 0.089 13 0.0859 90 1.25E-03 43 0.5 1.41 4.80 2.09 0.78 0.24 475 2.3 0.057 19 0.0125 64 2.07E-03 4 0.1 4.55 4.72 1.15 0.45 0.53 464 4.2 0.08 14 -0.226 6140 -1.97E-05 4364 0.71 1.17 5.78 2.07 0.57 0.32 500 3.8 0.056 16 0.0041 306 1.83E-03 11 0.0 -0.51 5.82 1.93 0.64 0.35 506 2.3 0.042 19 0.0501 59 2.31E-03 13 0.2 0.31 5.92 1.74 0.68 0.36 459 2.6 0.049 20 0.0255 60 1.83E-03 18 0.3 -0.01 5.72 2.10 0.63 0.37 494 3.6 0.046 19 0.0497 87 1.48E-03 28 0.3 -2.06 5.80 1.77 0.69 0.51 508 2.7 0.030 20 0.0222 65 2.09E-03 7 0.1 0.57 5.97 1.94 0.99 0.60 469 2.3 0.051 7 0.0181 22 2.16E-03 3 0.1 3.11 5.72 1.83 0.68 0.38 493 3.7 0.071 17 0.0194 32 1.69E-03 20 0.6 1.85 5.90 1.87 0.60 0.41 488 5.8 0.061 19 0.0093 188 1.98E-03 10 0.1 -0.26 5.88 2.27 0.83 1.05 523 3.1 0.044 14 0.0055 177 1.86E-03 6 0.0 0.42 5.93 2.19 0.58 0.40 506 2.1 0.050 18 0.0003 8085 1.86E-03 10 0.0 -0.80 5.51 0.73 0.63 0.23 499 1.3 0.040 12 0.0036 244 1.94E-03 4 0.0 4.16 5.50 0.90 0.60 0.96 483 2.6 0.080 17 0.0266 28 1.65E-03 13 0.5 2.28 5.42 0.63 0.67 0.82 503 1.0 0.065 12 0.0166 19 1.70E-03 12 0.6 -0.66 5.53 0.52 0.73 0.18 503 1.4 0.041 10 0.0017 433 1.88E-03 5 0.0 0.31 5.35 0.46 0.83 3.11 510 1.4 0.049 11 0.0132 11 1.96E-03 1 0.1 -0.07 5.55 0.76 0.50 0.66 517 3.4 0.046 16 0.0240 58 2.03E-03 7 0.1 -0.20 5.54 0.95 0.58 0.27 508 2.5 0.045 14 0.0019 531 1.85E-03 7 0.0 -0.07 5.69 0.30 0.60 0.63 517 1.8 0.046 12 0.0007 1589 1.83E-03 6 0.0 -0.28 5.34 0.53 0.67 1.32 490 1.5 0.044 10 0.0150 31 2.06E-03 2 0.1 1.11 5.55 0.89 0.80 0.75 496 1.1 0.055 7 0.0148 13 2.01E-03 1 0.1 -0.02 5.48 0.85 0.60 1.51 513 2.9 0.046 11 0.0124 12 1.95E-03 3 0.3 -0.12 4.87 1.23 0.75 0.32 498 1.5 0.045 10 0.0032 292 1.93E-03 4 0.0 -0.01 5.55 0.84 0.56 0.61 490 3.2 0.046 17 0.0051 182 1.89E-03 10 0.1 0.46 5.24 1.02 0.36 0.43 513 4.6 0.050 17 0.0123 23 1.73E-03 13 0.6 -1.04 5.63 0.76 0.64 0.64 501 1.3 0.038 12 0.0010 971 1.90E-03 5 0.0 -0.27 5.58 0.67 0.71 0.78 493 2.3 0.044 9 0.0054 128 1.97E-03 4 0.0 0.39 5.41 1.87 0.93 0.81 506 1.4 0.049 6 0.0043 156 1.90E-03 3 0.0 -0.57 5.66 1.54 1.07 0.86 519 0.6 0.042 18 0.0083 49 1.90E-03 2 0.0 0.37 5.34 1.17 0.81 0.34 511 2.0 0.049 9 0.0007 2147 1.85E-03 7 0.0 -0.67 5.26 1.58 0.86 1.35 513 1.4 0.041 9 0.0002 6433 1.85E-03 6 0.0 -0.45 5.59 1.52 0.98 0.51 516 2.1 0.043 8 0.0146 20 1.71E-03 7 0.4 -0.40 5.72 1.08 1.01 1.57 506 1.7 0.043 6 0.0102 20 1.96E-03 2 0.1 0.76 5.38 1.88 0.64 1.78 491 1.6 0.052 18 0.0068 120 1.97E-03 4 0.0 2.24 4.55 5.56 0.77 4.97 452 10.8 0.064 9 0.0112 53 2.14E-03 11 0.2 1.38 4.84 0.28 0.82 0.60 515 3.2 0.057 9 0.0010 599 1.80E-03 5 0.0 13.49 5.57 28.63 1.08 2.07 818 32.6 0.153 15 0.0020 526 1.02E-03 34 0.1 -1.46 6.02 2.04 0.58 0.49 513 7.1 0.035 26 0.0591 69 2.38E-03 19 0.3 1.32 4.71 2.18 0.82 0.31 504 2.9 0.057 18 0.0233 69 2.05E-03 8 0.1 4.47 5.74 2.46 0.42 0.78 533 5.4 0.082 25 0.0005 9466 1.70E-03 24 0.0 2.91 5.77 1.22 0.64 0.35 468 3.4 0.069 16 0.0266 49 2.19E-03 7 0.1 14.84 5.20 2.59 0.75 0.78 421 3.4 0.164 8 0.0281 76 2.15E-03 10 0.1 24.07 3.98 3.24 1.04 0.84 300 15.1 0.237 21 0.0670 46 2.97E-03 16 0.4 3.49 5.45 0.97 0.69 0.99 527 5.1 0.074 17 0.0059 349 1.78E-03 11 0.0 4.54 5.01 2.31 0.73 0.31 466 2.3 0.082 14 0.0980 102 1.08E-03 50 0.5 0.39 5.11 0.98 0.81 0.63 469 1.4 0.049 10 0.0073 71 2.07E-03 3 0.0 4.65 5.10 1.74 0.54 0.47 451 1.0 0.083 16 0.0254 16 2.22E-03 1 0.1 1.83 5.11 1.83 1.19 0.22 464 2.3 0.061 11 0.0384 24 2.33E-03 4 0.2 0.97 5.17 1.95 0.35 0.20 461 2.2 0.054 7 0.0161 7 2.17E-03 2 0.3 1.24 5.06 1.17 0.89 2.80 460 1.6 0.056 7 0.0056 84 2.08E-03 3 0.0 1.61 5.10 0.95 0.86 1.50 465 4.6 0.059 16 0.0281 36 2.24E-03 6 0.2 0.28 5.11 1.54 0.72 0.16 479 2.4 0.049 8 0.0098 31 2.05E-03 3 0.1 2.76 4.93 2.66 0.59 7.02 527 7.1 0.068 9 0.0035 183 1.71E-03 9 0.0 5.93 4.59 2.70 0.94 0.18 441 2.0 0.093 11 0.0155 43 2.15E-03 3 0.1 5.01 5.10 1.41 0.29 0.71 429 2.8 0.086 17 0.0148 59 1.96E-03 14 0.2 0.88 5.15 1.48 1.23 0.15 476 0.6 0.053 8 0.0180 15 2.12E-03 1 0.1 1.64 4.62 1.64 0.35 0.36 467 2.3 0.059 12 0.0019 279 2.00E-03 3 0.0 0.57 5.13 1.65 1.01 0.76 479 3.5 0.051 5 0.0095 23 2.04E-03 4 0.2 0.78 5.03 1.05 1.00 0.12 456 1.5 0.053 5 0.0171 8 2.20E-03 2 0.2 1.14 4.95 0.38 0.66 0.26 476 3.1 0.055 19 0.0058 134 2.01E-03 4 0.0 5.64 4.78 1.81 0.57 4.50 466 3.6 0.091 7 0.0175 15 1.76E-03 7 0.4 2.13 4.97 1.20 0.71 0.55 486 2.2 0.063 8 0.0123 33 2.01E-03 3 0.1 0.08 5.14 1.67 0.33 2.05 485 3.6 0.047 4 0.0124 7 2.05E-03 4 0.5 1.37 4.98 1.81 0.50 0.85 469 3.3 0.057 7 0.0187 12 2.15E-03 3 0.3 0.70 4.90 2.02 0.47 0.87 463 3.5 0.052 11 0.0028 269 2.05E-03 5 0.0 1.40 5.09 2.95 0.65 1.34 443 0.6 0.057 6 0.0092 43 2.18E-03 2 0.0 1.60 5.52 2.24 0.37 1.24 488 2.2 0.059 4 0.0123 15 2.01E-03 2 0.2 1.42 5.12 1.48 0.58 2.63 472 3.2 0.058 3 0.0153 7 2.10E-03 3 0.4 0.60 5.54 2.72 0.81 1.30 470 1.8 0.051 4 0.0101 17 2.09E-03 2 0.1 1.94 4.74 7.96 0.79 16 387 11.6 0.062 6 0.0016 403 2.41E-03 12 0.0 1.04 5.63 20.59 0.50 0.80 639 15.3 0.054 4 0.0046 42 1.50E-03 15 0.4 -0.24 5.39 2.67 0.41 0.20 454 2.1 0.044 4 0.0112 10 2.18E-03 2 0.2 0.51 5.19 2.11 0.32 1.68 451 4.4 0.050 3 0.0115 12 2.18E-03 4 0.4 6.37 4.90 0.45 0.50 2.47 433 1.9 0.097 11 0.0307 11 2.31E-03 2 0.2 1.18 4.96 1.30 0.28 0.33 507 5.1 0.056 5 0.0108 21 1.93E-03 5 0.2 0.00 5.24 1.39 1.18 4.32 470 2.7 0.046 6 0.0040 92 2.04E-03 3 0.0 0.71 5.03 1.87 0.40 0.96 495 4.3 0.052 3 0.0112 11 1.99E-03 4 0.4 0.16 5.28 0.68 1.08 0.70 481 4.6 0.048 3 0.0115 10 2.06E-03 5 0.5 0.75 4.74 1.80 0.63 1.49 459 2.0 0.052 6 0.0021 216 2.06E-03 3 0.0 0.38 5.17 1.63 0.32 0.10 480 2.9 0.049 4 0.0123 9 2.07E-03 3 0.3 1.20 7.16 11.25 0.59 7.63 635 17.3 0.056 10 0.0198 48 1.64E-03 18 0.4 2.52 5.08 3.94 0.40 1.00 494 4.6 0.066 13 0.0066 420 1.92E-03 14 0.0 4.92 5.14 1.69 0.24 7.32 480 4.3 0.085 16 0.0305 131 2.13E-03 19 0.1 3.32 5.07 4.38 0.29 6.32 475 3.1 0.073 15 0.0571 54 2.42E-03 14 0.3 4.03 5.14 0.59 0.25 1.53 461 1.0 0.078 14 0.0266 42 1.74E-03 23 0.5 13.69 5.15 1.69 0.39 1.12 403 1.0 0.154 9 0.0292 125 2.27E-03 15 0.1 0.89 5.09 1.24 0.25 1.48 441 2.6 0.053 19 0.0368 98 2.44E-03 15 0.2 0.27 5.22 2.15 0.54 0.72 443 1.1 0.048 7 0.0030 237 2.15E-03 3 0.0 4.45 4.88 6.28 0.37 0.94 423 13.9 0.081 10 0.0162 158 2.27E-03 17 0.1 8.94 4.82 4.45 0.37 1.05 402 5.6 0.117 11 0.0132 295 2.26E-03 17 0.1 23.14 4.57 1.98 0.22 3.42 335 3.2 0.229 9 0.1917 262 5.04E-04 176 0.7 2.67 4.88 4.33 0.27 3.25 420 5.9 0.067 16 0.0121 103 2.08E-03 21 0.2 3.76 4.91 4.26 0.28 2.84 366 8.6 0.076 15 0.0212 255 2.67E-03 21 0.1 6.75 5.39 3.8 0.33 3.47 508 6.2 0.100 16 0.0191 258 0.00190 25.2 0.1 1.04 5.80 6.7 1.52 2.46 512 19.7 0.055 11 0.0122 30 0.00193 19.7 0.6 13.19 4.99 5.0 0.55 3.22 446 9.1 0.151 11 0.0204 83 0.00166 29.1 0.4 6.21 4.87 1.5 0.46 1.61 477 5.1 0.095 14 0.0014 3095 0.00184 22.5 0.0 1.36 4.95 4.5 1.48 3.05 501 5.4 0.057 4 0.0140 17 0.00198 5.5 0.3 6.38 4.89 0.5 0.52 0.44 460 7.3 0.097 12 0.0739 44 0.00256 15.4 0.4 3.10 4.93 1.3 0.63 0.95 468 1.4 0.071 8 0.0045 320 0.00199 6.6 0.0 7.38 5.45 5.2 0.43 2.18 436 5.2 0.105 17 0.0434 123 0.00238 23.2 0.2 4.11 4.99 5.6 0.38 3.55 425 1.2 0.079 18 0.0576 93 0.00163 37.5 0.4 3.76 5.43 4.1 0.62 1.07 422 8.2 0.076 13 0.0294 94 0.00241 13.7 0.1 Table S2. In situ zircon trace element concentrations (ppm) red/pink: ananomalous, likely due to inclusion analysis; not considered representative of zircon composition Sample TE Spot name TE notes Li Be B F Na Al P K Ca Sc Ti ÁrE1 ArE1301-1.1 0.78 3.32 0.24 89.85 2156.10 1153.11 279.29 184.44 49.52 37.50 12.44 ArE1301-1.2 0.00 1.40 0.07 11.57 2.53 10.43 290.67 1.91 1.02 65.66 13.98 ArE1301-2.1 0.01 2.92 0.03 23.95 1.94 11.09 296.15 1.61 1.19 43.61 12.58 ArE1301-3.1 0.59 37.19 0.14 96.89 4.13 32.50 326.21 32.93 15.59 30.16 29.74 ArE1301-4.1 0.39 155.35 1.57 32.66 2.09 4.01 408.49 1.61 1.12 19.68 6.22 ArE1301-5.1 0.05 7.46 0.06 28.87 15.61 6.85 251.32 6.17 2.44 50.43 10.67 ArE1301-6.1 4.64 22.75 0.10 69.37 4.16 12.95 276.58 8.71 11.09 45.07 7.07 ArE1301-7.1 1.68 1.03 0.03 18.12 1.74 6.76 282.66 1.48 2.53 42.31 11.22 ÁrE3 ArE1303-2.1 0.11 3.21 0.14 0.00 3.47 6.59 210.29 5.79 5.43 8.51 15.65 ArE1303-3.1 0.00 1.43 0.02 3.85 4.60 9.21 380.21 9.42 7.58 12.53 20.61 ArE1303-4.1 Same grain! Core 0.12 9.97 0.10 2.42 3.20 5.51 253.26 6.53 5.21 7.19 15.91 ArE1303-5.1 Same grain! Rim 0.12 14.99 0.07 7.44 3.36 6.67 252.40 6.17 5.25 9.65 10.13 ArE1303-6.1 0.01 3.15 0.13 2.52 3.65 7.42 287.74 6.43 5.95 8.77 12.21 ArE1303-7.1 0.00 38.93 0.91 12.24 3.20 6.21 286.71 6.86 6.10 8.02 14.53 ArE1303-8.1 0.02 69.98 0.44 2.42 3.22 5.50 282.44 6.14 4.62 8.95 14.63 ArE1303-9.1 0.01 63.63 0.49 4.76 3.27 7.12 247.63 7.57 2.99 9.79 12.91 ArE1303-10.2 Spot location matches U-Pb 0.06 11.56 1.04 0.00 3.61 8.94 386.40 7.48 5.53 11.33 10.41 ArE1303-10.1 Low-U rim 0.12 1.10 0.54 0.00 30.35 35.41 264.93 96.12 213.91 14.87 11.17 ArE1303-11.1 0.00 2.18 0.16 2.28 2.46 4.18 133.76 4.58 3.13 4.73 11.95 ArE1303-12.1 0.00 4.88 0.32 0.00 2.23 4.89 253.37 5.11 4.46 8.63 14.35 ArE1303-13.1 Spot location matches U-Pb 0.02 76.61 0.11 3.89 2.56 5.47 296.26 5.98 4.47 7.92 15.67 ArE1303-13.2 On rim of same grain 0.00 1.84 0.10 2.13 1.88 4.55 230.64 3.66 2.15 13.72 11.58 ArE1303-14.1 0.00 2.73 0.16 0.00 3.69 7.45 236.20 7.04 6.35 9.08 14.41 ArE1303-15.1 Very odd! Maybe beam issues? 0.00 1.42 0.24 0.00 3.28 5.10 227.09 5.26 2.68 9.27 15.47 ÁrE4: Mount TJB.7 ArE1304-1.1 0.39 155.35 1.57 32.66 2.09 4.01 408.49 1.61 1.12 19.68 6.22 ArE1304-2.1 0.19 185.42 1.35 38.88 1.96 4.06 393.77 1.90 1.01 17.86 7.00 ArE1304-3.1 0.91 411.53 4.19 92.67 2.87 5.06 435.41 1.94 1.30 30.35 6.98 ArE1304-4.1 0.28 138.66 1.36 50.69 11.23 4.94 294.76 1.82 1.65 17.35 6.55 ArE1304-5.1 0.33 191.58 1.43 36.96 798.37 691.73 528.50 1828.43 57.67 64.66 16.21 ArE1304-6.1 0.39 98.60 0.55 13.43 3.50 5.82 182.43 2.64 1.37 45.21 9.71 ArE1304-7.1 0.05 100.59 1.14 32.03 3.17 7.22 245.81 3.65 3.95 20.68 5.89 ArE1304-8.1 0.19 165.96 2.79 29.53 2.71 4.76 369.67 2.66 1.44 38.59 9.13 ArE1304-9.1 0.31 193.03 1.26 17.69 2.32 4.15 237.33 2.42 1.63 43.92 9.77 ArE1304-10.1 0.25 167.73 2.24 47.98 2.68 4.71 359.27 2.72 1.05 26.42 5.87 ArE1304-11.1 0.08 80.94 0.47 14.22 3.21 8.48 279.32 1.87 1.29 55.21 9.41 ArE1304-12.1 2.19 372.66 2.24 57.50 2.56 4.83 388.62 1.87 1.02 32.28 8.51 ArE1304-13.1 0.00 21.08 0.10 3.73 3.63 4.35 189.83 2.23 1.35 25.12 6.18 ArE1304-14.1 0.01 155.73 1.00 56.13 2.40 4.37 326.41 1.98 1.19 24.24 4.91 ArE1304-15.1 0.84 253.57 6.93 84.96 112.08 48.75 338.76 72.11 8.86 55.13 13.74 ArE1304-16.1 1.47 106.61 0.47 22.75 3.72 4.40 237.43 2.47 1.98 36.47 7.13 ÁrE4: Mount TJB.8 ArE1304-1.1 0.29 305.93 4.02 24.34 2.30 4.54 1010.85 1.03 2.05 85.49 8.51 ArE1304-2.1 1.93 370.20 2.15 25.36 6.05 5.39 619.42 4.10 100.49 100.18 15.17 ArE1304-3.1 0.04 143.98 1.14 6.77 2.14 5.34 545.07 0.98 5.08 72.89 15.73 ArE1304-4.1 0.11 74.56 1.31 46.36 6.39 7.82 380.18 2.74 4.15 52.32 14.09 ArE1304-5.1 3.09 112.84 0.81 18.50 5.14 13.11 592.56 1.93 2.79 58.50 12.18 ArE1304-6.1 1.75 299.32 2.03 16.02 2.63 3.93 684.84 3.74 2.45 81.91 10.33 ArE1304-7.1 0.01 19.93 0.23 10.92 26.35 12.72 261.32 2.19 1.60 26.93 6.46 DH (all) DH08-1.1 0.26 12.84 0.29 2.46 5.59 5.66 153.58 5.92 3.25 6.49 11.78 DH08-3.1 0.00 0.03 0.25 2.45 6.70 7.85 129.04 7.51 53.78 5.94 12.94 DH08-4.1 0.01 1.64 0.07 6.38 31.07 38.33 152.58 66.03 72.14 6.80 11.89 DH08-5.1 69.16 242.16 0.84 41.35 35.66 21.10 453.51 32.77 235.35 9.06 15.45 DH08-6.1 3.22 9.63 0.13 3.08 3.43 8.58 243.20 5.34 4.89 7.62 14.76 DH08-9.1 38.91 78.23 0.34 11.80 11.40 6.97 235.84 12.45 66.40 4.39 11.17 DH15-1.1 0.23 35.65 1.24 70.34 53.17 30.63 156.32 30.34 133.23 9.78 12.72 DH15-11 0.33 34.74 1.05 8.10 76.44 68.89 334.17 28.91 72.21 16.43 20.91 HfE2
11.51 HfE3 Fe Y Nb La Ce Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Pb Th U Eu/Eu* Th/U 4.78 3080 21.65 5.33 24.18 4.22 9.60 2.41 89.89 18.58 211 120 264 62 421 71 4194 0.246 49 0.25 0.66 2.40 1334 13.04 0.02 8.52 0.93 3.33 0.95 30.43 11.77 129 53 232 50 420 74 9121 0.266 36 0.29 0.35 2.52 2727 10.55 0.04 7.83 2.96 8.84 2.72 89.51 30.11 319 118 469 94 732 123 8293 0.154 71 0.29 0.63 3.21 3222 21.57 0.30 19.27 4.18 10.77 2.35 104.78 31.46 346 143 517 101 737 129 8143 0.297 135 0.21 0.71 2.61 3677 23.11 0.02 21.59 3.59 9.18 2.47 97.86 33.02 381 145 588 115 867 147 9651 0.199 104 0.25 0.62 2.60 1535 15.59 0.02 8.17 1.20 3.53 0.98 34.26 12.63 142 57 241 49 393 68 9070 0.175 50 0.27 0.53 2.47 1430 18.01 1.74 15.60 4.40 6.39 1.25 44.81 15.18 163 63 242 50 386 68 8995 0.209 92 0.22 0.77 2.52 2429 9.47 0.04 7.23 2.72 8.05 2.26 62.68 22.76 244 91 363 72 568 98 7422 0.154 57 0.31 0.62 0.48 731 12.25 0.02 8.81 0.63 1.79 0.64 20.59 7.34 83 31 131 26 203 34 9211 0.19 8 0.32 0.42 1.33 1234 22.72 0.02 15.97 1.06 3.15 0.92 29.65 11.97 134 48 216 42 346 57 14273 0.33 24 0.29 0.31 1.22 906 15.33 0.03 10.82 0.86 2.81 0.81 23.24 9.31 104 37 162 32 247 42 8718 0.09 31 0.30 0.61 2.81 975 21.25 0.02 14.13 0.95 2.44 0.46 25.02 9.11 103 38 175 35 287 48 10688 0.09 33 0.18 0.42 0.34 1012 24.03 0.03 14.70 1.03 2.70 0.55 26.51 9.67 110 41 175 36 271 47 10235 0.18 40 0.20 0.50 105.41 2290 13.25 0.08 12.62 4.79 7.92 2.42 77.20 25.98 268 95 380 73 530 84 8679 0.15 46 0.30 0.62 0.25 2316 12.56 0.05 11.50 4.41 8.40 2.51 75.37 25.62 270 97 390 74 556 88 9270 0.16 58 0.30 0.65 0.52 1914 10.40 0.04 10.93 4.34 8.19 2.14 64.67 21.15 217 78 308 58 425 71 8988 0.19 38 0.28 0.63 158.44 2850 23.52 0.03 19.61 4.04 9.60 2.02 87.43 33.16 343 123 511 100 767 121 10017 0.26 101 0.21 0.69 20.28 873 14.85 0.03 13.28 0.53 1.97 0.42 20.15 8.29 93 33 159 31 268 44 10475 0.14 40 0.21 0.49 0.25 463 10.77 0.02 7.66 0.37 1.14 0.32 10.92 4.04 48 19 84 17 129 22 9242 0.08 11 0.27 0.44 1.13 861 18.54 0.03 11.65 0.70 2.47 0.61 22.26 8.84 99 36 152 32 251 41 9441 0.13 35 0.25 0.61 38.85 2678 16.50 0.04 13.66 4.82 11.47 3.35 103.63 34.19 348 124 485 91 649 99 7783 0.16 66 0.30 0.72 2.61 833 13.99 0.01 11.25 0.65 1.99 0.42 19.80 7.29 88 34 151 32 262 44 10848 0.15 31 0.20 0.43 14.78 585 14.26 0.02 10.14 0.72 2.31 0.61 21.97 8.38 94 36 153 32 261 42 10178 0.25 23 0.26 0.43 0.28 795 14.43 0.03 9.74 0.79 2.59 0.72 20.05 7.84 24 34 47 10 85 15 3996 0.05 10 0.30 0.46 2.61 3677 23.11 0.02 21.59 3.59 9.18 2.47 97.86 33.02 381 145 588 115 867 147 9651 0.20 104 0.25 0.62 2.58 4295 32.64 0.06 34.24 6.05 16.02 4.71 165.60 56.09 592 218 870 169 1238 206 8775 0.42 207 0.28 0.78 2.63 6180 46.76 0.08 52.22 7.71 21.72 5.47 218.90 72.27 768 280 1107 210 1547 253 8944 0.64 279 0.24 0.83 2.53 2698 19.36 0.17 25.01 2.68 8.20 1.46 84.36 33.72 365 136 558 112 840 138 10150 0.44 139 0.17 0.67 2.67 3772 80.91 11.77 366.69 13.92 14.45 3.09 116.91 41.13 446 165 654 126 953 159 9021 0.49 266 0.23 0.83 2.52 1998 5.87 0.03 6.50 2.97 7.97 2.82 71.37 23.30 250 89 365 77 579 100 8099 0.09 41 0.36 0.58 2.48 1116 15.93 1.92 42.80 2.50 3.00 0.60 24.95 7.38 88 36 145 30 243 41 9649 0.15 21 0.21 0.45 2.39 2607 32.60 0.02 24.82 2.10 6.41 1.90 75.01 26.66 306 112 474 93 728 126 9170 0.36 130 0.26 0.68 2.47 2388 10.68 0.02 15.28 3.48 9.79 2.61 99.67 35.11 384 138 585 117 922 154 9219 0.38 134 0.25 0.66 2.47 2834 19.42 0.03 17.06 2.69 7.56 1.79 78.98 27.66 315 121 497 99 759 127 9990 0.23 86 0.22 0.59 2.60 3055 9.60 0.03 7.67 3.94 11.70 4.57 110.57 37.19 393 139 552 108 836 142 8077 0.22 69 0.39 0.65 2.50 4900 30.51 0.05 27.05 5.61 16.55 4.67 157.03 53.08 555 207 816 159 1213 197 8617 0.33 161 0.28 0.70 2.63 834 19.38 0.01 7.81 0.35 1.48 0.32 16.78 6.04 75 32 134 29 235 42 10625 0.09 22 0.20 0.39 2.52 2071 41.11 0.06 26.11 1.54 4.06 0.74 48.06 16.56 197 80 343 69 549 95 10558 0.22 69 0.16 0.46 2.59 4579 29.54 0.49 28.46 6.91 19.00 4.94 163.25 55.17 581 211 830 164 1239 201 8535 0.42 187 0.27 0.85 2.33 2666 14.18 0.06 14.46 3.70 9.95 2.62 87.49 28.84 305 117 471 93 715 123 8546 0.20 81 0.27 0.64 2.42 6037 101.07 0.12 110.96 5.35 16.83 3.44 170.20 55.70 644 256 997 198 1478 250 8581 0.93 409 0.20 0.84 2.17 5626 81.36 1.09 61.45 8.08 22.76 5.97 218.09 64.38 679 260 941 190 1343 223 7992 0.74 585 0.26 1.32 2.63 3537 72.19 0.10 48.22 3.09 10.17 2.81 113.38 37.71 420 154 608 123 907 153 9189 0.99 606 0.25 1.33 2.52 2334 34.48 0.08 29.53 1.79 6.33 1.73 70.41 24.03 266 101 410 80 614 105 8902 0.49 323 0.25 1.10 2.43 3722 110.36 0.03 64.89 4.06 14.68 3.68 146.55 48.45 516 186 728 139 1043 175 8276 1.18 863 0.24 1.37 2.48 5755 187.43 0.04 120.43 4.98 16.68 4.23 176.31 60.76 688 252 1004 195 1442 240 8717 0.93 443 0.24 0.85 2.46 1001 16.40 0.08 12.57 0.78 1.90 0.53 22.02 7.67 97 39 175 38 304 55 9848 0.22 38 0.25 0.43 1.95 2054 10.12 0.04 8.22 3.62 6.85 2.83 70.28 24.17 245 87 348 65 494 75 7770 0.06 46 0.39 0.65 0.71 590 9.94 0.02 5.58 0.44 1.68 0.61 16.71 5.95 68 24 108 22 177 27 7213 0.14 12 0.35 0.38 2.49 1619 6.75 0.05 7.11 3.91 6.22 2.48 56.79 21.17 214 74 299 57 419 70 8518 0.15 28 0.40 31.41 0.77 2836 82.01 0.07 50.40 3.03 8.95 2.86 77.66 23.75 258 96 355 67 471 72 6876 0.41 190 0.33 0.98 3.39 1588 31.71 0.06 1.46 1.86 5.08 1.99 49.45 15.60 180 73 274 52 385 61 7480 0.12 56 0.38 0.64 1.36 3398 25.07 0.03 15.56 5.81 13.74 4.49 119.87 39.32 407 141 549 99 733 115 7529 0.11 91 0.34 0.71 3.46 2548 15.34 0.09 13.39 5.50 12.62 4.75 103.52 31.96 330 125 454 85 620 98 7048 0.17 75 0.40 0.72 30.74 2257 42.82 0.18 30.15 4.00 8.75 2.75 71.60 23.24 239 93 340 62 463 75 8304 0.56 183 0.34 1.12 145.57 7351 --0.14 25.87 7.63 24.59 6.02 227.99 --786 --1143 --1627 --9007 --161 0.24 0.78 14.47 2683 --0.05 3.00 2.75 9.00 3.27 81.51 --289 --461 --733 --7470 --29 0.37 0.53 16.58 2266 --0.37 22.74 2.25 7.10 1.91 74.13 --259 --386 --584 --8308 --176 0.25 1.15 8.46 4275 --0.02 12.62 0.74 4.19 1.42 65.95 --377 --747 --1267 --10539 --140 0.26 0.34 104.50 7273 --0.07 57.18 5.38 20.14 5.18 211.70 --762 --1131 --1645 --9282 --339 0.24 0.86 2.26 1148 --0.45 7.29 1.18 3.06 0.93 30.97 --123 --206 --330 --7431 --55 0.29 0.83 250.43 10844 --0.11 38.35 8.12 28.12 7.23 284.28 --1060 --1605 --2311 --9579 --255 0.25 0.69 53.63 3707 --3.60 19.08 4.35 10.99 2.68 102.96 --387 --622 --931 --7058 --86 0.24 0.58 811.68 6986 --1.20 42.63 6.53 21.12 5.63 205.66 --719 --1061 --1506 --7603 --352 0.26 0.91 3.72 1229 --0.02 1.90 0.60 1.84 0.79 20.15 --109 --232 --423 --6956 --10 0.40 0.28 32.29 4350 --0.82 51.48 3.78 14.61 3.54 147.09 --496 --717 --1025 --8821 --374 0.23 1.19 57.4 4622 1.87 17 2.5 4.7 1.1 60 343 724 1299 10440 195 0.209 0.34 255.6 11116 0.08 83 8.0 28.0 6.5 274 1037 1613 2358 8934 807 0.225 0.98 21.9 3403 0.37 44 1.7 6.7 2.1 77 324 567 948 10296 701 0.285 0.97 4.2 2323 0.18 15 1.2 4.2 1.4 50 229 400 643 9358 109 0.285 0.64 325.7 3046 2.00 17 2.5 5.8 1.5 62 275 492 804 7237 138 0.237 0.56 5.0 2852 0.27 23 1.6 5.2 1.5 63 275 479 764 9816 188 0.255 0.69 181.1 15361 0.30 17 1.0 7.0 2.0 148 994 2190 3737 13183 500 0.192 0.32 50.3 2926 0.12 17 0.9 4.4 1.2 55 272 511 868 10282 182 0.238 0.48 10.3 2335 0.64 16 0.9 3.7 1.1 47 224 405 668 9188 91 0.257 0.45 31.2 3393 1.09 35 2.8 6.5 1.6 67 302 555 973 9476 243 0.236 0.63 243.5 8150 2.45 27 1.9 7.3 2.1 104 607 1288 2249 13443 321 0.227 0.36 180.8 9218 0.22 44 2.5 10.8 2.8 144 717 1314 2221 11185 727 0.214 0.56 58.2 6558 0.13 60 2.4 11.2 2.6 138 616 1076 1755 12419 735 0.201 0.79 93.6 4714 0.58 36 2.6 9.5 2.4 102 446 657 1095 10547 354 0.236 0.77 167.0 8127 0.24 20 1.0 6.3 2.2 113 697 1367 2435 11612 367 0.250 0.48 231.8 11111 0.60 31 1.7 8.8 2.3 143 885 1754 3067 14260 528 0.196 0.39 166.2 18967 0.51 19 1.2 8.2 2.4 171 1210 2638 4578 15929 528 0.196 0.31 49.0 2033 0.21 7 1.8 4.8 1.4 50 204 352 565 9491 41 0.284 0.48 138.9 8261 25.47 85 24.8 22.1 3.4 146 582 1096 1839 10494 151 0.180 0.27 186.9 9234 0.19 120 10.2 31.5 3.8 296 977 1415 1925 9019 558 0.119 1.14 257.5 13844 0.30 26 1.0 7.2 2.4 144 939 1963 3368 12494 711 0.226 0.39 314.4 18395 0.06 101 6.1 26.2 4.0 319 1419 2463 3857 8474 1611 0.132 1.04 45.8 3761 2.09 35 3.9 8.4 2.2 81 325 590 1037 7824 297 0.253 0.61 173.9 15478 0.87 17 1.1 6.8 2.0 144 996 2189 3789 13418 445 0.196 0.31 102.7 1325 0.60 7 1.1 3.1 0.8 30.8 129 233 407 8123 42 0.235 0.61 4.9 1227 0.06 8 0.7 2.5 0.6 24.7 125 224 371 8849 37 0.248 0.48 279.8 3124 0.10 7 2.2 7.0 2.3 74.7 295 511 835 8684 69 0.304 0.62 7.1 1076 1.87 7 1.6 2.6 0.6 21.4 98 186 335 8491 25 0.235 0.45 6.6 1099 0.13 6 0.6 2.0 0.5 21.3 103 200 354 9534 22 0.250 0.39 255.7 6510 0.09 35 6.3 17.0 4.0 193.5 683 1155 1769 9366 237 0.213 0.94 100.2 2402 1.87 9 3.1 6.8 1.6 62.9 234 391 650 8593 56 0.236 0.63 3.7 1152 0.21 6 0.8 2.1 0.6 24.5 111 203 382 9375 24 0.248 0.37 25.5 925 1.11 5 0.7 1.8 0.5 18.3 77 154 277 7121 16 0.243 0.34 572.5 11194 0.21 63 9.7 26.2 4.5 266.3 1049 1643 2425 9133 415 0.163 0.84 2.3 918 0.02 5 0.4 1.7 0.5 18.6 87 166 291 8468 18 0.270 0.39 1.9 1117 0.31 7 0.8 2.2 0.6 24.0 105 202 347 8720 28 0.238 0.45 49.5 2428 0.03 6 1.7 5.7 1.8 63.9 254 438 728 8478 71 0.283 0.65 0.8 846 0.16 4 0.4 1.4 0.5 18 88 152 275 9944 13 0.281 0.41 286.6 2706 0.43 7 2.7 7.4 2.0 75 299 509 771 8605 55 0.263 0.60 51.1 3258 2.46 30 4.4 8.7 2.1 85 327 541 801 8080 133 0.241 0.61 41.4 1068 1.12 8 1.5 2.7 0.7 24 104 188 312 7357 26 0.274 0.45 425.1 23313 0.86 470 24.1 63.3 7.2 637 2238 3151 4259 10325 1933 0.109 1.47 518.1 11562 30.45 308 26.4 20.8 3.1 122 630 1312 2940 7877 1751 0.187 1.44 0.6 1086 1.21 7 1.0 2.0 0.6 23 105 198 370 9538 16 0.254 0.32 40.0 1850 163.67 179 85.0 30.4 4.4 94 208 302 448 8355 35 0.251 0.50 0.1 1505 0.08 11 0.9 3.1 1.0 34 158 254 454 8977 39 0.293 0.53 8.4 897 0.28 6 0.8 1.8 0.5 18 83 163 292 8464 15 0.249 0.36 Yb/Gd Hf/Yb Yb/Nb Th/Nb Gd/Nd Yb/Nd Sm/Nd Ce/Sm U/Yb Sc/Yb Ce/Yb Gd/Yb Nb/Yb Nd/Yb T (°C) 4.68 9.97 19.43 2.28 21.31 99.76 2.28 2.52 0.18 0.09 0.06 0.21 0.05 0.0100 13.81 21.71 32.21 2.73 32.81 452.95 3.59 2.56 0.24 0.16 0.02 0.07 0.03 0.0022 8.18 11.33 69.42 6.74 30.27 247.56 2.99 0.89 0.15 0.06 0.01 0.12 0.01 0.0040 7.03 11.05 34.16 6.24 25.09 176.42 2.58 1.79 0.26 0.04 0.03 0.14 0.03 0.0057 8.86 11.13 37.52 4.50 27.29 241.71 2.56 2.35 0.19 0.02 0.02 0.11 0.03 0.0041 11.47 23.08 25.21 3.19 28.50 326.92 2.94 2.31 0.24 0.13 0.02 0.09 0.04 0.0031 8.61 23.31 21.42 5.08 10.19 87.75 1.45 2.44 0.31 0.12 0.04 0.12 0.05 0.0114 9.06 13.07 60.00 6.01 23.02 208.61 2.96 0.90 0.16 0.07 0.01 0.11 0.02 0.0048 9.88 45.30 16.60 0.63 32.89 324.85 2.87 4.91 0.09 0.04 0.04 0.10 0.06 0.0031 11.68 41.21 15.24 1.06 27.99 326.96 2.98 5.07 0.22 0.04 0.05 0.09 0.07 0.0031 10.65 35.24 16.14 2.03 27.10 288.53 3.28 3.84 0.21 0.03 0.04 0.09 0.06 0.0035 11.46 37.26 13.50 1.57 26.31 301.58 2.56 5.80 0.28 0.03 0.05 0.09 0.07 0.0033 10.22 37.78 11.28 1.66 25.72 262.79 2.62 5.44 0.29 0.03 0.05 0.10 0.09 0.0038 6.87 16.37 40.03 3.48 16.12 110.74 1.65 1.59 0.14 0.02 0.02 0.15 0.02 0.0090 7.37 16.68 44.22 4.58 17.08 125.94 1.90 1.37 0.16 0.02 0.02 0.14 0.02 0.0079 6.57 21.14 40.87 3.63 14.90 97.96 1.89 1.33 0.14 0.02 0.03 0.15 0.02 0.0102 8.77 13.07 32.59 4.29 21.62 189.50 2.37 2.04 0.19 0.01 0.03 0.11 0.03 0.0053 13.28 39.15 18.01 2.66 38.24 507.81 3.74 6.74 0.30 0.06 0.05 0.08 0.06 0.0020 11.84 71.48 12.00 1.00 29.69 351.59 3.10 6.72 0.19 0.04 0.06 0.08 0.08 0.0028 11.28 37.60 13.54 1.90 31.87 359.40 3.54 4.71 0.23 0.03 0.05 0.09 0.07 0.0028 6.26 11.99 39.33 4.02 21.49 134.58 2.38 1.19 0.14 0.01 0.02 0.16 0.03 0.0074 13.22 41.45 18.70 2.23 30.59 404.42 3.07 5.66 0.28 0.05 0.04 0.08 0.05 0.0025 11.90 38.93 18.34 1.59 30.44 362.19 3.19 4.40 0.20 0.03 0.04 0.08 0.05 0.0028 4.25 46.88 5.91 0.72 25.46 108.22 3.28 3.77 0.26 0.11 0.11 0.24 0.17 0.0092 8.86 11.13 37.52 4.50 27.29 241.71 2.56 2.35 0.19 0.02 0.02 0.11 0.03 0.0041 7.48 7.09 37.94 6.33 27.37 204.62 2.65 2.14 0.21 0.01 0.03 0.13 0.03 0.0049 7.07 5.78 33.09 5.96 28.39 200.68 2.82 2.40 0.22 0.02 0.03 0.14 0.03 0.0050 9.96 12.08 43.39 7.17 31.44 313.09 3.06 3.05 0.25 0.02 0.03 0.10 0.02 0.0032 8.16 9.46 11.78 3.29 8.40 68.49 1.04 25.37 0.34 0.07 0.38 0.12 0.08 0.0146 8.11 13.99 98.59 7.04 24.04 195.03 2.69 0.81 0.12 0.08 0.01 0.12 0.01 0.0051 9.73 39.74 15.24 1.30 10.00 97.25 1.20 14.25 0.19 0.09 0.18 0.10 0.07 0.0103 9.70 12.60 22.32 3.98 35.63 345.69 3.04 3.87 0.26 0.05 0.03 0.10 0.04 0.0029 9.25 10.00 86.30 12.56 28.66 264.98 2.82 1.56 0.22 0.05 0.02 0.11 0.01 0.0038 9.60 13.17 39.06 4.43 29.35 281.83 2.81 2.26 0.19 0.03 0.02 0.10 0.03 0.0035 7.56 9.66 87.11 7.21 28.10 212.46 2.97 0.66 0.13 0.07 0.01 0.13 0.01 0.0047 7.72 7.10 39.76 5.28 27.97 216.07 2.95 1.63 0.19 0.03 0.02 0.13 0.03 0.0046 14.04 45.12 12.15 1.13 47.90 672.38 4.21 5.30 0.24 0.11 0.03 0.07 0.08 0.0015 11.41 19.25 13.34 1.67 31.26 356.79 2.64 6.43 0.27 0.04 0.05 0.09 0.07 0.0028 7.59 6.89 41.93 6.34 23.62 179.24 2.75 1.50 0.18 0.04 0.02 0.13 0.02 0.0056 8.17 11.96 50.41 5.75 23.64 193.12 2.69 1.45 0.18 0.05 0.02 0.12 0.02 0.0052 8.68 5.81 14.62 4.04 31.82 276.26 3.15 6.59 0.33 0.06 0.08 0.12 0.07 0.0036 6.16 5.95 16.50 7.19 27.01 166.29 2.82 2.70 0.33 0.07 0.05 0.16 0.06 0.0060 8.00 10.13 12.57 8.40 36.65 293.30 3.29 4.74 0.50 0.08 0.05 0.12 0.08 0.0034 8.72 14.50 17.81 9.38 39.35 343.11 3.54 4.66 0.48 0.09 0.05 0.11 0.06 0.0029 7.11 7.94 9.45 7.82 36.08 256.69 3.62 4.42 0.60 0.06 0.06 0.14 0.11 0.0039 8.18 6.05 7.69 2.36 35.43 289.71 3.35 7.22 0.36 0.06 0.08 0.12 0.13 0.0035 13.81 32.39 18.53 2.30 28.23 389.78 2.43 6.63 0.29 0.09 0.04 0.07 0.05 0.0026 7.03 15.72 48.86 4.54 19.41 136.54 1.89 1.20 0.14 0.01 0.02 0.14 0.02 0.0073 10.60 40.73 17.82 1.22 37.87 401.22 3.80 3.33 0.18 0.03 0.03 0.09 0.06 0.0025 7.38 20.32 62.07 4.18 14.52 107.16 1.59 1.14 0.00 0.02 0.02 0.14 0.02 0.0093 6.07 14.59 5.75 2.31 25.62 155.49 2.95 5.63 0.41 0.02 0.11 0.16 0.17 0.0064 7.78 19.43 12.14 1.78 26.52 206.42 2.72 0.29 0.23 0.02 0.00 0.13 0.08 0.0048 6.12 10.27 29.25 3.63 20.64 126.28 2.37 1.13 0.17 0.01 0.02 0.16 0.03 0.0079 5.99 11.36 40.45 4.87 18.82 112.79 2.30 1.06 0.17 0.02 0.02 0.17 0.02 0.0089 6.46 17.95 10.80 4.27 17.89 115.57 2.19 3.45 0.35 0.04 0.07 0.15 0.09 0.0087 7.14 5.53 29.90 213.39 3.23 1.05 0.13 0.02 0.14 0.0047 8.99 10.19 29.61 266.24 3.27 0.33 0.07 0.00 0.11 0.0038 7.88 14.23 32.97 259.73 3.16 3.20 0.26 0.04 0.13 0.0039 19.22 8.32 89.12 1712.67 5.66 3.01 0.32 0.01 0.05 0.0006 7.77 5.64 39.35 305.80 3.74 2.84 0.24 0.03 0.13 0.0033 10.66 22.50 26.16 278.91 2.59 2.38 0.20 0.02 0.09 0.0036 8.13 4.15 35.02 284.71 3.46 1.36 0.16 0.02 0.12 0.0035 9.04 7.58 23.65 213.83 2.53 1.74 0.16 0.02 0.11 0.0047 7.32 5.05 31.50 230.67 3.23 2.02 0.26 0.03 0.14 0.0043 21.01 16.43 33.72 708.45 3.08 1.03 0.08 0.00 0.05 0.0014 6.97 8.60 38.92 271.36 3.87 3.52 0.31 0.05 0.14 0.0037 21.81 8.03 24.30 529.96 1.90 3.70 0.44 0.01 0.05 0.0019 8.59 3.79 34.37 295.43 3.51 2.95 0.35 0.04 0.12 0.0034 12.24 10.86 46.08 563.94 3.98 6.64 0.76 0.05 0.08 0.0018 12.75 14.55 43.28 551.81 3.59 3.48 0.27 0.02 0.08 0.0018 13.06 9.00 24.77 323.51 2.35 2.96 0.31 0.02 0.08 0.0031 12.10 12.85 39.55 478.59 3.23 4.43 0.36 0.03 0.08 0.0021 25.30 3.53 141.37 3576.94 6.68 2.38 0.42 0.00 0.04 0.0003 15.77 11.84 58.11 916.13 4.62 3.98 0.43 0.02 0.06 0.0011 14.11 13.74 50.91 718.32 4.01 4.24 0.30 0.02 0.07 0.0014 14.44 9.73 24.46 353.32 2.36 5.39 0.40 0.04 0.07 0.0028 21.67 5.98 54.98 1191.37 3.88 3.67 0.39 0.01 0.05 0.0008 15.45 5.04 56.71 876.28 4.27 4.10 0.58 0.02 0.06 0.0011 12.71 7.08 57.15 726.29 4.65 5.30 0.53 0.03 0.08 0.0014 10.70 9.63 38.68 414.04 3.59 3.79 0.42 0.03 0.09 0.0024 21.52 4.77 110.96 2388.34 6.20 3.20 0.31 0.01 0.05 0.0004 21.44 4.65 83.90 1798.85 5.17 3.54 0.44 0.01 0.05 0.0006 26.81 3.48 139.40 3737.61 6.67 2.28 0.37 0.00 0.04 0.0003 11.37 16.78 27.14 308.74 2.64 1.53 0.15 0.01 0.09 0.0032 12.60 5.71 5.89 74.27 0.89 3.84 0.31 0.05 0.08 0.0135 6.51 4.68 28.97 188.61 3.09 3.81 0.25 0.06 0.15 0.0053 23.45 3.71 147.81 3465.88 7.41 3.58 0.55 0.01 0.04 0.0003 12.09 2.20 52.42 633.75 4.30 3.87 0.40 0.03 0.08 0.0016 12.83 7.54 20.89 268.09 2.17 4.12 0.47 0.03 0.08 0.0037 26.40 3.54 136.35 3598.98 6.41 2.48 0.38 0.00 0.04 0.0003 13.21 19.98 27.50 363.36 2.78 2.35 0.17 0.02 0.08 0.0028 15.06 23.83 37.01 557.37 3.81 2.97 0.21 0.02 0.07 0.0018 11.19 10.40 33.22 371.68 3.11 0.97 0.13 0.01 0.09 0.0027 15.61 25.38 13.82 215.79 1.66 2.79 0.17 0.02 0.06 0.0046 16.60 26.91 35.80 594.43 3.37 2.96 0.16 0.02 0.06 0.0017 9.14 5.29 30.92 282.73 2.72 2.04 0.14 0.02 0.11 0.0035 10.33 13.22 20.04 206.99 2.17 1.34 0.14 0.01 0.10 0.0048 15.56 24.55 29.94 465.75 2.57 2.72 0.17 0.02 0.06 0.0021 15.16 25.66 25.25 382.70 2.53 2.91 0.17 0.02 0.07 0.0026 9.10 3.77 27.56 250.97 2.71 2.39 0.20 0.03 0.11 0.0040 15.69 29.07 44.78 702.37 4.03 3.03 0.16 0.02 0.06 0.0014 14.49 25.11 31.35 454.05 2.91 2.93 0.18 0.02 0.07 0.0022 11.39 11.64 37.59 428.07 3.38 1.07 0.15 0.01 0.09 0.0023 14.99 36.12 46.61 698.52 3.66 2.90 0.12 0.02 0.07 0.0014 10.30 11.16 28.21 290.45 2.78 0.97 0.12 0.01 0.10 0.0034 9.47 10.08 19.22 181.98 1.97 3.44 0.27 0.04 0.11 0.0055 12.92 23.59 15.80 204.05 1.74 3.09 0.19 0.03 0.08 0.0049 6.68 2.42 26.44 176.60 2.62 7.43 0.31 0.11 0.15 0.0057 24.07 2.68 4.63 111.47 0.79 14.79 0.41 0.10 0.04 0.0090 16.25 25.81 23.28 378.29 2.00 3.68 0.13 0.02 0.06 0.0026 4.77 18.66 1.10 5.26 0.36 5.87 0.16 0.40 0.21 0.1900 13.17 19.78 37.96 499.83 3.37 3.44 0.16 0.02 0.08 0.0020 16.06 28.99 22.42 360.12 2.26 3.04 0.14 0.02 0.06 0.0028 Table S3. Árnes, Hrafnsfjörður, and Kaldalón in situ zircon oxygen isotope compositions Total Error (2σ ext.) ÁrE3: Tr2 rhyolite ArE3_TJB06@1.ais TJB.6 1.67E+09 1.33E+06 3.37E+06 2.61E+03 2.89 1.16E-01 2.0110E-03 2.34E-07 0.00201187 3.33 0.77 ArE3_TJB06@2.ais TJB.6 1.67E+09 1.13E+06 3.37E+06 2.29E+03 3.06 8.92E-02 2.0113E-03 1.80E-07 0.00201222 3.50 0.75 ArE3_TJB06@3.ais TJB.6 1.68E+09 9.92E+05 3.37E+06 1.91E+03 3.22 8.62E-02 2.0116E-03 1.73E-07 0.00201253 3.66 0.75 ArE3_TJB06@4.ais TJB.6 1.67E+09 1.06E+06 3.36E+06 2.29E+03 3.20 1.06E-01 2.0116E-03 2.12E-07 0.00201249 3.64 0.76 ArE3_TJB06@5.ais TJB.6 1.67E+09 9.66E+05 3.36E+06 2.14E+03 3.20 1.19E-01 2.0116E-03 2.40E-07 0.00201249 3.64 0.77 ArE3_TJB06@6.ais TJB.6 1.67E+09 1.74E+06 3.37E+06 3.40E+03 3.30 1.15E-01 2.0118E-03 2.31E-07 0.00201271 3.74 0.77 ArE3_TJB06@7.ais TJB.6 1.67E+09 1.20E+06 3.36E+06 2.54E+03 3.49 1.35E-01 2.0122E-03 2.72E-07 0.00201308 3.93 0.78 ArE3_TJB06@8.ais TJB.6 1.67E+09 8.13E+05 3.37E+06 1.54E+03 2.84 6.24E-02 2.0109E-03 1.25E-07 0.00201179 3.28 0.74 ArE3_TJB06@9.ais TJB.6 1.67E+09 9.53E+05 3.35E+06 1.99E+03 2.91 1.21E-01 2.0110E-03 2.44E-07 0.00201192 3.35 0.77 ArE3_TJB06@10.ais TJB.6 1.69E+09 1.73E+06 3.40E+06 3.59E+03 2.44 1.03E-01 2.0101E-03 2.07E-07 0.00201099 2.89 0.76 ArE3_TJB06@11.ais TJB.6 1.68E+09 9.90E+05 3.37E+06 1.97E+03 3.39 7.83E-02 2.0120E-03 1.57E-07 0.00201287 3.83 0.75 ArE3_TJB06@12.ais TJB.6 1.67E+09 6.91E+05 3.36E+06 1.56E+03 3.53 1.24E-01 2.0123E-03 2.50E-07 0.00201317 3.97 0.77 ArE3_TJB06@13.ais TJB.6 1.67E+09 6.06E+05 3.37E+06 1.22E+03 3.27 1.32E-01 2.0118E-03 2.65E-07 0.00201264 3.71 0.78 ArE3_TJB06@14.ais TJB.6 1.68E+09 1.01E+06 3.37E+06 2.00E+03 2.91 7.56E-02 2.0110E-03 1.52E-07 0.00201192 3.35 0.75 ArE3_TJB06@15.ais TJB.6 1.67E+09 1.19E+06 3.37E+06 2.33E+03 3.40 1.44E-01 2.0120E-03 2.90E-07 0.00201291 3.84 0.79 ArE3_TJB06@16.ais TJB.6 1.67E+09 2.22E+06 3.37E+06 4.44E+03 3.14 1.12E-01 2.0115E-03 2.26E-07 0.00201238 3.58 0.77 ArE3_TJB06@17.ais TJB.6 1.68E+09 8.30E+05 3.38E+06 1.69E+03 2.65 8.92E-02 2.0105E-03 1.79E-07 0.00201140 3.09 0.75 ArE3_TJB06@18.ais TJB.6 1.67E+09 1.28E+06 3.36E+06 2.68E+03 3.77 1.01E-01 2.0128E-03 2.03E-07 0.00201364 4.21 0.76 ArE3_TJB06@19.ais TJB.6 1.67E+09 8.15E+05 3.36E+06 1.51E+03 3.09 6.16E-02 2.0114E-03 1.24E-07 0.00201227 3.53 0.74 ArE3_TJB06@20.ais TJB.6 1.67E+09 8.16E+05 3.36E+06 1.64E+03 3.21 1.29E-01 2.0116E-03 2.59E-07 0.00201252 3.65 0.78 ArE3_TJB06@21.ais TJB.6 1.66E+09 1.44E+06 3.34E+06 3.00E+03 2.91 9.35E-02 2.0110E-03 1.88E-07 0.00201192 3.35 0.76 ArE3_TJB06@22.ais TJB.6 1.66E+09 1.40E+06 3.34E+06 2.83E+03 2.96 9.50E-02 2.0111E-03 1.91E-07 0.00201202 3.40 0.76 ArE3_TJB06@23.ais TJB.6 1.67E+09 1.17E+06 3.36E+06 2.29E+03 3.41 9.13E-02 2.0120E-03 1.84E-07 0.00201292 3.85 0.76 ArE3_TJB06@24.ais TJB.6 1.67E+09 8.31E+05 3.36E+06 1.63E+03 2.86 1.06E-01 2.0109E-03 2.14E-07 0.00201181 3.30 0.76 ÁrE4: Tr3 rhyolite ArE4_TJB08@1.ais TJB.8 2.25E+09 5.23E+06 4.53E+06 1.05E+04 2.50 7.98E-02 2.0102E-03 1.61E-07 0.00201181 3.30 0.51 ArE4_TJB08@2.ais TJB.8 2.28E+09 1.78E+06 4.59E+06 3.74E+03 2.68 9.62E-02 2.0106E-03 1.93E-07 0.00201217 3.48 0.52 ArE4_TJB08@3.ais TJB.8 2.26E+09 5.19E+05 4.55E+06 1.21E+03 2.40 9.57E-02 2.0100E-03 1.92E-07 0.00201161 3.20 0.52 ArE4_TJB08@4.ais TJB.8 2.21E+09 1.02E+06 4.44E+06 1.86E+03 2.29 8.12E-02 2.0098E-03 1.63E-07 0.00201139 3.09 0.51 ArE4_TJB08@5.ais TJB.8 2.17E+09 6.73E+05 4.35E+06 1.32E+03 2.63 8.95E-02 2.0105E-03 1.80E-07 0.00201206 3.42 0.52 ArE4_TJB08@6.ais TJB.8 2.14E+09 1.75E+06 4.30E+06 3.38E+03 2.88 7.42E-02 2.0110E-03 1.49E-07 0.00201257 3.68 0.51 ArE4_TJB08@7.ais TJB.8 2.14E+09 2.65E+06 4.30E+06 5.36E+03 1.96 9.99E-02 2.0091E-03 2.01E-07 0.00201073 2.76 0.52 ArE4_TJB07@1.ais TJB.7 1.61E+09 9.79E+05 3.23E+06 2.06E+03 2.75 1.06E-01 2.0107E-03 2.13E-07 0.00201044 2.61 0.73 ArE4_TJB07@2.ais TJB.7 1.59E+09 1.87E+06 3.20E+06 3.76E+03 3.54 1.02E-01 2.0123E-03 2.05E-07 0.00201203 3.41 0.72 ArE4_TJB07@3.ais TJB.7 1.58E+09 1.69E+06 3.18E+06 3.46E+03 3.86 9.98E-02 2.0129E-03 2.01E-07 0.00201266 3.72 0.72 ArE4_TJB07@4.ais TJB.7 1.57E+09 2.19E+06 3.16E+06 4.53E+03 3.54 1.07E-01 2.0123E-03 2.16E-07 0.00201203 3.41 0.73 ArE4_TJB07@5.ais TJB.7 1.58E+09 1.04E+06 3.17E+06 2.18E+03 3.21 1.26E-01 2.0116E-03 2.53E-07 0.00201136 3.07 0.74 ArE4_TJB07@6.ais TJB.7 1.56E+09 7.10E+06 3.14E+06 1.42E+04 3.23 1.46E-01 2.0117E-03 2.93E-07 0.00201140 3.09 0.75 ArE4_TJB07@7.ais TJB.7 1.60E+09 1.65E+06 3.21E+06 3.42E+03 3.04 8.34E-02 2.0113E-03 1.68E-07 0.00201102 2.90 0.71 ArE4_TJB07@8.ais TJB.7 1.58E+09 1.54E+06 3.17E+06 2.90E+03 3.89 1.35E-01 2.0130E-03 2.71E-07 0.00201272 3.75 0.74 ArE4_TJB07@9.ais TJB.7 1.59E+09 1.45E+06 3.20E+06 2.96E+03 3.37 1.36E-01 2.0120E-03 2.74E-07 0.00201168 3.23 0.75 ArE4_TJB07@10.ais TJB.7 1.58E+09 1.36E+06 3.18E+06 2.87E+03 3.01 1.29E-01 2.0112E-03 2.59E-07 0.00201097 2.88 0.74 ArE4_TJB07@11.ais TJB.7 1.58E+09 1.89E+06 3.19E+06 3.99E+03 3.67 1.14E-01 2.0126E-03 2.29E-07 0.00201228 3.53 0.73 Spot Name Mount 16 O Measured 16 O Error 18 O Measured Corrected δ 18 O (‰) 18 O Error δ 18 O Raw δ 18 O Error 18 O/ 16 O Measured 18 O/ 16 O Error Corrected 18 O/ 16 O ArE4_TJB07@12.ais TJB.7 1.58E+09 1.28E+06 3.19E+06 2.55E+03 3.52 9.62E-02 2.0123E-03 1.94E-07 0.00201199 3.38 0.72 ArE4_TJB07@13.ais TJB.7 1.60E+09 1.56E+06 3.22E+06 3.20E+03 2.98 7.74E-02 2.0112E-03 1.56E-07 0.00201090 2.84 0.71 ArE4_TJB07@14.ais TJB.7 1.60E+09 1.66E+06 3.21E+06 3.31E+03 3.61 9.56E-02 2.0124E-03 1.92E-07 0.00201216 3.47 0.72 ArE4_TJB07@15.ais TJB.7 1.55E+09 8.85E+05 3.12E+06 1.64E+03 3.84 8.82E-02 2.0129E-03 1.78E-07 0.00201263 3.70 0.72 ArE4_TJB07@16.ais TJB.7 1.60E+09 1.39E+06 3.21E+06 2.69E+03 2.95 8.20E-02 2.0111E-03 1.65E-07 0.00201084 2.81 0.71 ÁrE1: Tr4 rhyolite ArE1_TJB07@1.ais TJB.7 1.58E+09 1.33E+06 3.19E+06 2.62E+03 3.60 1.08E-01 2.01E-03 2.17E-07 0.00201214 3.46 0.73 ArE1_TJB07@2.ais TJB.7 1.59E+09 7.29E+06 3.19E+06 1.47E+04 2.77 1.14E-01 2.01E-03 2.30E-07 0.00201048 2.63 0.73 ArE1_TJB07@3.ais TJB.7 1.58E+09 4.50E+05 3.17E+06 1.20E+03 3.76 1.62E-01 2.01E-03 3.26E-07 0.00201247 3.62 0.77 ArE1301_18-1.1 TJB.18 1.57 1.83E-01 3.45 0.24 ArE1301_18-2.1 TJB.18 1.62 2.64E-01 3.49 0.24 ArE1301_18-3.1 TJB.18 1.69 1.89E-01 3.48 0.16 ArE1301_18-4.1 TJB.18 1.40 2.06E-01 3.20 0.16 ArE1301_18-5.1 TJB.18 1.61 2.32E-01 3.41 0.16 ArE1301_18-6.1 TJB.18 1.43 2.22E-01 3.22 0.16 ArE1301_18-7.1 TJB.18 1.42 2.04E-01 3.22 0.16 DH-08: Tr1 rhyolite DH-08@1.ais TJB.9 4.51E+09 4.75E+06 9.07E+06 9.55E+03 0.00 1.00E-07 2.01E-03 2.01E-13 0.00201251 3.65 0.37 DH-08@2.ais TJB.9 4.54E+09 5.95E+06 9.13E+06 1.18E+04 0.00 7.92E-08 2.01E-03 1.59E-13 0.00201235 3.57 0.37 DH-08@3.ais TJB.9 4.47E+09 2.31E+06 8.99E+06 4.59E+03 0.00 8.81E-08 2.01E-03 1.77E-13 0.00201217 3.47 0.37 DH-08@4.ais TJB.9 4.42E+09 3.10E+06 8.89E+06 6.25E+03 0.00 8.21E-08 2.01E-03 1.65E-13 0.00201256 3.67 0.37 DH-08@5.ais TJB.9 4.38E+09 3.19E+06 8.80E+06 6.48E+03 0.00 8.25E-08 2.01E-03 1.66E-13 0.00201140 3.09 0.37 DH-08@6.ais TJB.9 4.39E+09 1.04E+07 8.82E+06 2.13E+04 0.00 1.10E-07 2.01E-03 2.22E-13 0.00201140 3.09 0.37 DH-08@7.ais TJB.9 4.48E+09 1.27E+07 9.01E+06 2.50E+04 0.00 1.33E-07 2.01E-03 2.68E-13 0.00201159 3.18 0.37 DH-15: Tr1 rhyolite DH-15@1.ais TJB.9 3.75E+09 3.82E+06 7.53E+06 7.26E+03 0.00 1.29E-07 2.01E-03 2.59E-13 0.00200998 2.38 0.37 DH-15@2.ais TJB.9 4.51E+09 1.11E+07 9.06E+06 2.23E+04 0.00 7.38E-08 2.01E-03 1.48E-13 0.00201116 2.97 0.37 DH-15@3.ais TJB.9 4.33E+09 7.46E+06 8.71E+06 1.50E+04 0.00 9.53E-08 2.01E-03 1.91E-13 0.00201089 2.84 0.37 DH-15@4.ais TJB.9 4.39E+09 1.02E+07 8.82E+06 2.05E+04 0.00 9.56E-08 2.01E-03 1.92E-13 0.00201067 2.73 0.37 DH-15@5.ais TJB.9 4.36E+09 1.11E+07 8.76E+06 2.21E+04 0.00 1.02E-07 2.01E-03 2.04E-13 0.00201109 2.94 0.37 DH-15@6.ais TJB.9 4.44E+09 8.54E+06 8.92E+06 1.75E+04 0.00 1.37E-07 2.01E-03 2.76E-13 0.00201299 3.89 0.37 DH-15@7.ais TJB.9 4.31E+09 2.02E+07 8.66E+06 4.05E+04 0.00 1.10E-07 2.01E-03 2.21E-13 0.00201073 2.76 0.37 DH-15@8.ais TJB.9 4.05E+09 8.23E+06 8.13E+06 1.61E+04 0.00 1.12E-07 2.00E-03 2.25E-13 0.00200665 0.73 0.37 DH-15@9.ais TJB.9 4.11E+09 2.06E+07 8.27E+06 4.18E+04 0.00 1.35E-07 2.01E-03 2.72E-13 0.00201076 2.77 0.37 DH-15@10.ais TJB.9 3.17E+09 3.34E+06 6.36E+06 6.50E+03 0.00 1.37E-07 2.01E-03 2.74E-13 0.00200937 2.08 0.37 HfE2: Tdb dacite (mapped) HfE2@3.ais TJB.11 3.27E+09 8.07E+06 6.58E+06 1.59E+04 1.69 7.63E-02 2.01E-03 1.53E-07 0.00201272 3.75 0.68 HfE2@4.ais TJB.11 3.35E+09 1.13E+07 6.72E+06 2.23E+04 0.71 7.62E-02 2.01E-03 1.53E-07 0.00201075 2.77 0.68 HfE2@6.ais TJB.11 3.32E+09 6.56E+06 6.66E+06 1.26E+04 1.33 1.35E-01 2.01E-03 2.72E-07 0.00201201 3.39 0.72 HfE2@8.ais TJB.11 3.28E+09 8.79E+06 6.59E+06 1.70E+04 1.72 1.29E-01 2.01E-03 2.59E-07 0.00201277 3.78 0.71 HfE2@10.ais TJB.11 3.31E+09 8.08E+06 6.64E+06 1.58E+04 1.63 8.84E-02 2.01E-03 1.77E-07 0.00201261 3.69 0.69 HfE2@12.ais TJB.11 3.04E+09 8.51E+06 6.11E+06 1.67E+04 2.05 9.98E-02 2.01E-03 2.01E-07 0.00201344 4.11 0.69 HfE3: dacite flow (?) HfE3@3.ais TJB.11 3.10E+09 8.63E+06 6.22E+06 1.73E+04 1.91 3.84E-02 2.01E-03 7.72E-08 0.00201316 3.97 0.67 HfE3@4.ais TJB.11 3.13E+09 4.87E+06 6.29E+06 9.59E+03 1.25 6.54E-02 2.01E-03 1.31E-07 0.00201184 3.31 0.68 HfE3@5.ais TJB.11 3.18E+09 3.92E+06 6.38E+06 6.91E+03 0.95 1.75E-01 2.01E-03 3.52E-07 0.00201123 3.01 0.75 HfE3@6.ais TJB.11 3.05E+09 1.91E+06 6.13E+06 3.39E+03 1.19 1.39E-01 2.01E-03 2.79E-07 0.00201172 3.25 0.72 HfE3@7.ais TJB.11 3.03E+09 4.76E+06 6.10E+06 9.72E+03 2.04 1.05E-01 2.01E-03 2.11E-07 0.00201343 4.11 0.70 HfE3@8.ais TJB.11 3.14E+09 5.47E+06 6.30E+06 1.07E+04 1.01 7.17E-02 2.01E-03 1.44E-07 0.00201135 3.07 0.68 HfE3@9.ais TJB.11 3.07E+09 4.36E+06 6.17E+06 8.28E+03 0.95 8.37E-02 2.01E-03 1.68E-07 0.00201122 3.00 0.68 HfE3@10.ais TJB.11 3.04E+09 5.58E+06 6.11E+06 1.08E+04 1.40 1.12E-01 2.01E-03 2.25E-07 0.00201215 3.46 0.70 HfE3@11.ais TJB.11 3.11E+09 6.02E+06 6.25E+06 1.15E+04 1.36 1.15E-01 2.01E-03 2.31E-07 0.00201205 3.42 0.70 HfE3@12.ais TJB.11 3.07E+09 4.76E+06 6.16E+06 9.41E+03 1.88 6.71E-02 2.01E-03 1.35E-07 0.00201310 3.94 0.68 HfE3@21.ais TJB.11 3.13E+09 6.14E+06 6.28E+06 1.19E+04 0.89 8.78E-02 2.01E-03 1.76E-07 0.00201112 2.95 0.69 HfE3@22.ais TJB.11 3.09E+09 3.89E+06 6.21E+06 7.29E+03 1.43 1.02E-01 2.01E-03 2.05E-07 0.00201220 3.49 0.69 HfE3@23.ais TJB.11 3.19E+09 8.75E+06 6.39E+06 1.73E+04 0.91 1.13E-01 2.01E-03 2.28E-07 0.00201115 2.97 0.70 HfE3@24.ais TJB.11 3.20E+09 6.98E+06 6.43E+06 1.39E+04 1.30 8.32E-02 2.01E-03 1.67E-07 0.00201195 3.36 0.68 HfE3@15.ais TJB.11 3.26E+09 6.71E+06 6.55E+06 1.29E+04 0.93 1.03E-01 2.01E-03 2.08E-07 0.00201120 2.99 0.70 HfE3@17.ais TJB.11 3.26E+09 6.24E+06 6.54E+06 1.19E+04 1.32 1.17E-01 2.01E-03 2.35E-07 0.00201198 3.38 0.70 HfE3@18.ais TJB.11 3.43E+09 1.10E+07 6.87E+06 2.18E+04 -1.37 7.31E-02 2.00E-03 1.46E-07 0.00200658 0.69 0.68 HfE3@19.ais TJB.11 3.35E+09 9.83E+06 6.72E+06 1.92E+04 1.05 8.57E-02 2.01E-03 1.72E-07 0.00201143 3.10 0.69 HfE3@20.ais TJB.11 3.37E+09 8.57E+06 6.76E+06 1.72E+04 0.98 9.49E-02 2.01E-03 1.90E-07 0.00201129 3.04 0.69 KlE1: Kaldalón rhyolite 1 KlE1@1.ais TJB.11 2.99E+09 1.33E+07 5.99E+06 2.65E+04 0.08 7.20E-02 2.01E-03 1.44E-07 0.58065938 2.14 0.73 KlE1@10.ais TJB.11 3.41E+09 8.62E+06 6.83E+06 1.65E+04 0.21 1.18E-01 2.01E-03 2.36E-07 0.94854982 2.27 0.75 KlE1@12.ais TJB.11 3.34E+09 8.09E+06 6.70E+06 1.59E+04 0.25 7.08E-02 2.01E-03 1.42E-07 0.57055786 2.31 0.73 KlE1@13.ais TJB.11 3.31E+09 1.05E+07 6.64E+06 2.07E+04 0.62 1.06E-01 2.01E-03 2.12E-07 0.85244257 2.68 0.75 KlE1@14.ais TJB.11 3.36E+09 1.16E+07 6.74E+06 2.26E+04 0.22 1.08E-01 2.01E-03 2.17E-07 0.87310569 2.28 0.75 KlE1@15.ais TJB.11 3.32E+09 4.80E+06 6.66E+06 9.38E+03 0.80 1.48E-01 2.01E-03 2.97E-07 1.19240560 2.86 0.77 KlE1@16.ais TJB.11 3.43E+09 8.90E+06 6.86E+06 1.73E+04 -1.58 1.12E-01 2.00E-03 2.24E-07 0.90090782 0.47 0.75 KlE1@17.ais TJB.11 3.35E+09 9.87E+06 6.71E+06 1.89E+04 -0.87 1.29E-01 2.00E-03 2.59E-07 1.04056912 1.18 0.76 KlE1@18.ais TJB.11 3.40E+09 8.51E+06 6.82E+06 1.64E+04 0.53 1.27E-01 2.01E-03 2.56E-07 1.02796177 2.59 0.76 KlE1@19.ais TJB.11 3.39E+09 9.67E+06 6.81E+06 1.90E+04 0.59 8.93E-02 2.01E-03 1.79E-07 0.72036277 2.64 0.74 KlE1@20.ais TJB.11 3.44E+09 7.44E+06 6.91E+06 1.46E+04 -0.04 1.14E-01 2.01E-03 2.28E-07 0.91850699 2.01 0.75 KlE1@5.ais TJB.11 3.42E+09 9.97E+06 6.84E+06 1.92E+04 -3.00 1.42E-01 2.00E-03 2.84E-07 1.14579243 -0.95 0.77 KlE1@6.ais TJB.11 3.41E+09 4.97E+06 6.84E+06 9.84E+03 -0.25 7.20E-02 2.00E-03 1.44E-07 0.58058858 1.80 0.73 KlE1@9.ais TJB.11 3.39E+09 9.13E+06 6.81E+06 1.80E+04 0.13 1.19E-01 2.01E-03 2.39E-07 0.96029120 2.18 0.75 KlE2: Kaldalón rhyolite 2 KlE2@1.ais TJB.11 3.35E+09 9.28E+06 6.73E+06 1.79E+04 0.76 1.15E-01 2.01E-03 2.31E-07 0.00201085 2.82 0.75 KlE2@11.ais TJB.11 3.37E+09 8.45E+06 6.76E+06 1.68E+04 1.23 7.31E-02 2.01E-03 1.47E-07 0.00201180 3.29 0.73 KlE2@12.ais TJB.11 3.34E+09 9.66E+06 6.71E+06 1.89E+04 0.37 9.19E-02 2.01E-03 1.84E-07 0.00201007 2.43 0.74 KlE2@13.ais TJB.11 3.32E+09 1.03E+07 6.67E+06 2.00E+04 0.55 1.25E-01 2.01E-03 2.50E-07 0.00201044 2.61 0.76 KlE2@14.ais TJB.11 3.27E+09 8.80E+06 6.57E+06 1.71E+04 0.75 1.02E-01 2.01E-03 2.04E-07 0.00201083 2.81 0.74 KlE2@15.ais TJB.11 3.29E+09 7.67E+06 6.60E+06 1.49E+04 0.57 7.91E-02 2.01E-03 1.59E-07 0.00201048 2.63 0.73 KlE2@4.ais TJB.11 3.29E+09 1.04E+07 6.60E+06 2.01E+04 -0.13 1.31E-01 2.00E-03 2.62E-07 0.00200906 1.93 0.76 KlE2@6.ais TJB.11 3.30E+09 7.95E+06 6.62E+06 1.55E+04 0.57 0.1042596 2.01E-03 2.0918E-07 0.00201046 2.63 0.74 KlE2@7.ais TJB.11 3.36E+09 8.50E+06 6.75E+06 1.66E+04 1.53 0.1227347 2.01E-03 2.4648E-07 0.00201240 3.59 0.76 KlE2@9.ais TJB.11 3.34E+09 7.53E+06 6.71E+06 1.49E+04 1.48 0.07489565 2.01E-03 1.504E-07 0.00201229 3.54 0.73 RED analysis is partially off the grain or on an inclusion or crack; considered unviable not included in sample average 0.12 0.09 0.09 0.11 0.12 0.11 0.14 0.06 0.12 0.10 0.08 0.12 0.13 0.08 0.14 0.11 0.09 0.10 0.06 0.13 0.09 0.09 0.09 0.11 0.08 0.10 0.10 0.08 0.09 0.07 0.10 0.11 0.10 0.10 0.11 0.13 0.15 0.08 0.13 0.14 0.13 0.11 Internal Error (1σ) 0.10 0.08 0.10 0.09 0.08 0.11 0.11 0.16 0.09 0.13 0.09 0.10 0.12 0.11 0.10 0.05 0.04 0.04 0.04 0.04 0.06 0.07 0.06 0.04 0.05 0.05 0.05 0.07 0.05 0.06 0.07 0.07 0.08 0.08 0.14 0.13 0.09 0.10 0.04 0.07 0.18 0.14 0.10 0.07 At WiscSIMS, UW-Madison 0.08 0.11 0.11 0.07 0.09 0.10 0.11 0.08 0.10 0.12 0.07 0.09 0.09 0.07 0.12 0.07 0.11 0.11 0.15 0.11 0.13 0.13 0.09 0.11 0.14 0.07 0.12 0.11 0.07 0.09 0.12 0.10 0.08 0.13 0.10 0.12 0.07 Supplemental Table S4. In situ zircon hafnium isotope compositions 176 Hf/ 177 Hf 2SE 176 Lu/ 177 Hf 2SE 176 Yb/ 177 Hf 2SE 178 Hf/ 177 Hf 2SE Árnes: Tr1 Rhyolite (ÁrE2) DH-04-1 0.283107 0.000040 0.00138 0.00003 0.03682 0.00084 1.467148 0.000060 DH-04-3 0.283117 0.000043 0.00233 0.00018 0.06520 0.00500 1.467140 0.000063 DH-04-4 0.283139 0.000049 0.00287 0.00013 0.08030 0.00390 1.467152 0.000055 Árnes: Tr2 Rhyolite (ÁrE3) ArE1303_10.1_ 0.283108 0.000042 0.00141 0.00005 0.04020 0.00150 1.467137 0.000060 ArE1303_11.1_ 0.283134 0.000029 0.00062 0.00001 0.01699 0.00017 1.467155 0.000037 ArE1303_12.1_ 0.283161 0.000027 0.00123 0.00001 0.03398 0.00040 1.467149 0.000043 ArE1303_12.2_ 0.283169 0.000022 0.00080 0.00001 0.02190 0.00014 1.467188 0.000037 ArE1303_13.1_ 0.283124 0.000035 0.00169 0.00003 0.04890 0.00100 1.467149 0.000053 ArE1303_14.1_ 0.283144 0.000032 0.00211 0.00016 0.06220 0.00490 1.467194 0.000042 ArE1303_15.1_ 0.283140 0.000027 0.00077 0.00003 0.02160 0.00100 1.467166 0.000035 ArE1303_2.1_ 0.283145 0.000024 0.00114 0.00002 0.03125 0.00049 1.467133 0.000021 ArE1303_26.1_ 0.283138 0.000042 0.00148 0.00016 0.04300 0.00510 1.467124 0.000045 ArE1303_27.1_ 0.283148 0.000037 0.00294 0.00032 0.08500 0.00970 1.467142 0.000040 ArE1303_3.1_ 0.283105 0.000032 0.00070 0.00001 0.01875 0.00042 1.467148 0.000035 ArE1303_4.1_ 0.283154 0.000030 0.00120 0.00002 0.03372 0.00067 1.467139 0.000040 ArE1303_6.1_ 0.283130 0.000028 0.00081 0.00001 0.02224 0.00038 1.467099 0.000044 ArE1303_8.1_ 0.283163 0.000032 0.00217 0.00008 0.06340 0.00270 1.467180 0.000036 ArE1303_9.1_ 0.283158 0.000037 0.00232 0.00010 0.06690 0.00300 1.467162 0.000042 Árnes: Tr3 Rhyolite (ÁrE4) ArE1304_7_1.1_ 0.283121 0.000044 0.00282 0.00014 0.08020 0.00350 1.467174 0.000045 ArE1304_7_10.1_ 0.283202 0.000046 0.00238 0.00003 0.06762 0.00076 1.467131 0.000049 ArE1304_7_11.1_ 0.283165 0.000031 0.00296 0.00010 0.08680 0.00280 1.467127 0.000032 ArE1304_7_12.1_ 0.283165 0.000043 0.00443 0.00008 0.12900 0.00280 1.467179 0.000049 ArE1304_7_13.1_ 0.283145 0.000029 0.00236 0.00011 0.06730 0.00300 1.467124 0.000042 ArE1304_7_15.1_ 0.283163 0.000043 0.00304 0.00003 0.08760 0.00150 1.467100 0.000043 ArE1304_7_16.1_ 0.283169 0.000033 0.00349 0.00019 0.10120 0.00670 1.467180 0.000036 ArE1304_7_2.1_ 0.283187 0.000043 0.00535 0.00013 0.14980 0.00390 1.467160 0.000046 ArE1304_7_3.1_ 0.283135 0.000043 0.00494 0.00010 0.13900 0.00280 1.467163 0.000043 ArE1304_7_4.1_ 0.283136 0.000030 0.00373 0.00009 0.10300 0.00240 1.467170 0.000041 ArE1304_7_5.1_ 0.283119 0.000057 0.00484 0.00008 0.13960 0.00280 1.467170 0.000044 ArE1304_7_6.1_ 0.283150 0.000036 0.00334 0.00012 0.09160 0.00360 1.467124 0.000041 ArE1304_7_7.1_ 0.283116 0.000048 0.00197 0.00007 0.05890 0.00210 1.467121 0.000047 ArE1304_7_8.1_ 0.283197 0.000045 0.00421 0.00032 0.11850 0.00920 1.467149 0.000028 ArE1304_7_9.1_ 0.283132 0.000048 0.00201 0.00009 0.05590 0.00200 1.467156 0.000067 Árnes: Tr4 Rhyolite (ÁrE1) ArE1301_3.1_ 0.283136 0.000049 0.002756 0.000040 0.077100 0.00150 1.467151 0.000049 Hrafnfjörður: KK-24 Dacite kk24_3 0.283192 0.000032 0.002832 0.000071 0.073792 0.002000 1.467253 0.000049 kk24_4 0.283238 0.000038 0.005540 0.000209 0.154466 0.006595 1.467276 0.000071 kk24_4b 0.283194 0.000052 0.004215 0.000102 0.117026 0.003131 1.467210 0.000073 kk24_5 0.283220 0.000022 0.004604 0.000043 0.126084 0.001340 1.467217 0.000050 kk24_6 0.283264 0.000042 0.002669 0.000080 0.072009 0.002625 1.467215 0.000060 kk24_7 0.283213 0.000054 0.004732 0.000202 0.130152 0.005858 1.467203 0.000050 kk24_8 0.283232 0.000033 0.003966 0.000066 0.108907 0.002061 1.467234 0.000042 kk24_8b 0.283223 0.000033 0.002498 0.000085 0.067850 0.002674 1.467212 0.000042 kk24_9 0.283219 0.000046 0.005607 0.000097 0.155701 0.002860 1.467241 0.000033 kk24_9b 0.283253 0.000033 0.004368 0.000227 0.125151 0.007835 1.467221 0.000042 kk24_10 0.283225 0.000061 0.005950 0.000065 0.170196 0.001769 1.467266 0.000045 kk24_11 0.283236 0.000039 0.004564 0.000232 0.129999 0.006326 1.467241 0.000052 kk24_11b 0.283219 0.000029 0.003469 0.000149 0.096956 0.004069 1.467250 0.000057 kk24_12 0.283266 0.000059 0.005559 0.000334 0.161310 0.009820 1.467190 0.000050 Hrafnfjörður: HfE2 Dacite HfE1402_3.1 0.283245 0.000036 0.004619 0.000026 0.2063 0.0059 1.467269 0.000050 HfE1402_6.1 0.283216 0.000035 0.004320 0.000260 0.1880 0.0150 1.467252 0.000049 HfE1402_10.1 0.283193 0.000034 0.003066 0.000026 0.1245 0.0046 1.467255 0.000043 Hrafnfjörður: HfE3 Andesite HfE1403_3.1 0.283229 0.000037 0.00477 0.00025 0.2020 0.0120 1.467279 0.000054 HfE1403_4.1 0.283224 0.000025 0.0054 0.00015 0.2233 0.0021 1.467279 0.00004 HfE1403_5.1 0.283197 0.000045 0.00673 0.000460 0.2800 0.0260 1.467214 0.000045 HfE1403_6.1 0.283259 0.000038 0.006592 0.000053 0.2800 0.0100 1.467243 0.000038 HfE1403_22.1 0.283244 0.000042 0.004450 0.000460 0.1850 0.0250 1.467236 0.00005 HfE1403_15.1 0.283275 0.000030 0.007655 0.000097 0.3272 0.0065 1.467244 0.000031 HfE1403_17.1 0.283231 0.000035 0.006608 0.000097 0.2862 0.0082 1.467247 0.00004 Kaldalón: KlE1 Rhyolite KlE1401_2.1 0.283204 0.000041 0.002149 0.000047 0.0840 0.0062 1.467213 0.000063 KlE1401_6.1 0.283242 0.000039 0.004880 0.000180 0.2080 0.0130 1.467242 0.000047 KlE1401_9.1 0.283236 0.000034 0.002716 0.000049 0.1113 0.0039 1.467217 0.000038 KlE1401_10.1 0.283200 0.000028 0.001980 0.000120 0.0858 0.0081 1.467292 0.000056 KlE1401_18.1 0.283236 0.000031 0.002960 0.000170 0.1225 0.0045 1.467255 0.000038 Kaldalón: KlE2 Rhyolite KlE1402_7.1 0.283223 0.000031 0.002310 0.000200 0.0959 0.0066 1.467275 0.000051 KlE1402_9.1 0.283213 0.000037 0.002900 0.000180 0.1218 0.0047 1.467221 0.000056 KlE1402_13.1 0.283188 0.000031 0.001966 0.000049 0.0839 0.0023 1.467278 0.000039 KlE1402_10.1 0.283196 0.000031 0.001512 0.000052 0.0618 0.0054 1.467226 0.000051 180 Hf/ 177 Hf 2SE TotalHfBeam εHf 2 SE Average εHf 2SD n Number of outliers 11.9 1.2 3 0 1.887060 0.000160 7.34 11.4 1.4 1.886860 0.000130 7.39 11.7 1.5 1.887100 0.000130 7.28 12.5 1.7 12.6 1.3 15 0 1.887090 0.000180 14.89 11.4 1.5 1.886987 0.000098 11.77 12.3 1.0 1.886980 0.000095 10.59 13.3 1.0 1.886937 0.000081 13.51 13.6 0.8 1.887020 0.000100 11.25 12.0 1.2 1.886930 0.000110 13.05 12.7 1.1 1.886950 0.000100 12.71 12.5 1.0 1.886940 0.000110 13.67 12.7 0.8 1.886840 0.000120 13.20 12.5 1.5 1.886940 0.000110 16.44 12.8 1.3 1.887010 0.000110 12.36 11.3 1.1 1.886929 0.000099 12.11 13.0 1.1 1.886860 0.000100 14.26 12.2 1.0 1.887015 0.000098 12.22 13.4 1.1 1.886900 0.000120 12.51 13.2 1.3 13.0 2.0 15 0 1.887080 0.000180 13.57 11.9 1.6 1.886780 0.000160 15.70 14.7 1.6 1.886840 0.000140 12.05 13.4 1.1 1.886890 0.000140 11.91 13.4 1.5 1.886910 0.000130 11.66 12.7 1.0 1.886950 0.000120 10.96 13.4 1.5 1.886965 0.000093 10.86 13.6 1.2 1.886926 0.000094 12.85 14.2 1.5 1.887040 0.000130 12.63 12.4 1.5 1.886956 0.000097 12.48 12.4 1.1 1.887110 0.000130 11.32 11.8 2.0 1.887070 0.000110 10.87 12.9 1.3 1.887120 0.000140 14.03 11.7 1.7 1.886990 0.000130 12.93 14.6 1.6 1.887030 0.000140 11.38 12.3 1.7 12.4 --1 1.886970 0.000160 15.35 12.4 1.7 15.7 1.6 14 ----4.70 14.4 1.1 ----5.41 16.0 1.4 ----5.54 14.5 1.9 ----7.02 15.4 0.8 ----5.42 16.9 1.5 ----6.89 15.1 1.9 ----6.47 15.8 1.2 ----6.31 15.5 1.2 ----6.63 15.4 1.6 ----6.24 16.5 1.2 ----6.81 15.6 2.2 ----6.13 15.9 1.4 ----6.13 15.4 1.1 ----5.98 17.0 2.1 15.3 1.8 3 1.886710 0.000120 13.81 16.3 1.3 1.886843 0.000089 14.30 15.2 1.2 1.886720 0.000120 10.38 14.4 1.2 16.0 1.8 7 1.88675 0.00012 13.49 15.7 1.3 1.88687 0.0001 19.17 15.5 0.9 1.88686 0.00011 16.50 14.6 1.6 1.886806 0.000083 23.20 16.8 1.3 1.88675 0.00012 20.20 16.2 1.5 1.886763 0.000086 23.40 17.3 1.1 1.886772 0.00008 22.44 15.8 1.2 15.5 1.4 5 1.886790 0.000130 10.00 14.8 1.4 1.886801 0.000091 13.01 16.2 1.4 1.886660 0.000140 10.74 15.9 1.2 1.886770 0.000110 12.34 14.7 1.0 1.886670 0.000130 12.72 15.9 1.1 14.9 1.1 4 1.886700 0.000130 10.70 15.5 1.1 1.886726 0.000098 11.18 15.1 1.3 1.886820 0.000100 12.49 14.3 1.1 1.886835 0.000095 11.63 14.5 1.1 Supplemental Table S5. Petrography of Árnes and Hrafnsfjörður rocks ÁrE1301/ÁrE1 (Tr4 rhyolite) Mineralogy Plagioclase Cpx Mode 15% 5% ÁrE1302/ÁrE2 (mapped as Tr1 rhyolite; basaltic-andesite) Mineralogy Plagioclase (C?)px Opaques Alteration Min. Mode 60% 10% 30% trace ÁrE1303/ÁrE3 (Tr2 rhyolite) Mineralogy Plagioclase Cpx Alteration min. Mode 18% 12% 10% Description Porphyritic with glass-dominated groundmass. Textures V.f.g. microlites and subhedral laths ≤ 30 x 30 µm; lineated to produce trachytic texture; in groundmass with glass ≤20 x 20 µm subhedral to anhedral grains, equant to elongate ≤20 x 20 µm eu-to subhedral grains, equant, evenly distributed; likely Mt based on magnetism of hand sample Something brown Textures 10% as eu-to subhedral tabular phenocrysts; range from 150 x 150 µm to 1.1 x 1.1 mm; oscillatory zoning common; ubiquitous simple twins; 5% as v.f.g. microlites in groundmass glass to yield felty texture Eu-to subhedral; max size 250 x 400 µm, avg. 200 x 100 µm; occasional embayments and skeletal grains Description Equigranular, fine-grained w/ homogeneous mineralogy in plag/px/mt; slight lineation esp. in plag sub-horizontal; rare plag + px phenos (<5 in thin section) Textures As phenocrysts, avg. ~750 x 700 µm, but glomerocrysts up to 2.5x2.5 mm; elongate to tabular, eu-to subhedral; zoning common 2 populations, each ~50% of cpx total: 1) altered to brown and sometimes completely replaced; 2) relatively unaltered. Both pops have microlite inclusions in xtals, sub-to anhedral. Avg. ~ 350 x 500 µm; max ~1.25 mm x 500 µm. Pop 1 xtals esp. form glomerocrysts w/in and near plag. Brown and orange ÁrE1304/ÁrE4 (Tr3 rhyolite, top) Mineralogy Plagioclase Cpx Opaques Mode 55% <2% 3% ÁrE1305/ÁrE5 (Tr3 rhyolite, bottom) Mineralogy Plagioclase Cpx Mode 15% 5% Textures up to 2.5x2.5 mm; elongate to tabular, eu-to subhedral; zoning common brown and sometimes completely replaced; 2) relatively unaltered. Both pops have microlite inclusions in xtals, sub-to anhedral. Avg. ~ 350 x 500 µm; max ~1.25 mm x 500 µm. Pop 1 xtals esp. form glomerocrysts w/in and near plag. Description Porphyritic. Groundmass (70%) is vfg and glassy, with dendritic cystallites in some areas. Textures 40% as phenocrysts; max size 1.5x1 mm, avg. ~ 1x1 mm; eu-to subhedral, zoned rims common; many grains with diffuse edges; a few small glomerocrysts <1.5 mm; 15% in g'mass <100 x 100 µm; eu-to anhedral, tabular to elongate; felty texture Eu-to anhedral phenos ~150x150 µm or smaller; sometimes ratty or embayed <50x50 µm, equant, square x-section; likely Mt Description Porphyritic with 40% glassy groundmass. Textures Phenocrysts; max size 1.5x1 mm, avg. ~ 1x1 mm; eu-to subhedral, zoned rims common Phenos ~200 x 200 µm; subhedral Description Porphyritic with 80% glassy groundmass. HfE1401/HfE1 (Hrafnsfjörður andesite [Tad]) Mineralogy Plagioclase Opx Cpx Opaques Alteration min. Mode 50% 20% 15% 15% trace HfE1402/HfE2 (Hrafnsfjörður dacite dome [Tdh]) Mineralogy Plagioclase Hbl (?) Fayalite Opaques Alteration min. Mode 40% <5% 5% 5% trace HfE1403/HfE13 (Hrafnsfjörður lava[?]) Mineralogy Plagioclase Opx Cpx Opaques Quartz Alteration min. Mode 47% 15% 5% 8% 5% 5% Description Porphyritic with 80% glassy groundmass. Textures 40% as f.g. g'mass; equigranular 100x20 µm, eusubhedral; aligned and often distorted around phenos; trachytic texture; 10% phenos 1 mm x 400 µm max; eu-subhedral tabs, zoned with relict rxn rim; some melt inclusions; frequently sub-horizontal w/ lineation Sub-to anhedral, equigranular, slightly elongate to equant; avg. ~40 x 20 µm, occasional grains up to 100 x 40 µm Anhedral and elongate to equant; avg. 40 x 30 µm, a few grains up to 100 x 60 µm Eu-to anhedral; square x-section; 100x100 µm max, avg. 40 x 40 µm Brown, diffuse Description Microporphyritic w/ aphanitic g-mass in thin section (hand sample is all aphanitic), w/ plag + px phenos in g'mass displaying hoziontal/sub-horizontal lineation that phenos almost all follow. G'mass roughly equigranular. Plag phenos have relict rxn rims indicating multi-stage histories. Lineation from post-eruption flow??? Textures 30% phenocrysts alined w/ lineation, 10% in g'mass; euhedral laths to subhedral w/shreddy edges; avg. 20 x 5 µm (>90% of phenos) but from 75x15 µm to vfg in g'mass; trachytic texture Elongate to needle-like; subhedral w/ ratty edges; undergoing replacement? Sub-and anhedral and patchy/ratty; <100 x 100 µm avg. <<50 x 50 µm, equant, square xsection, euhedral; likely Mt Brown alteration min. in g'mass, but not in plag Description Aphanitic, equigranular in hand sample and very dark; thin section is microporphyritic w/ at least 2 iterations of plag as phenos, along with hbl (?) and fayalite. G'mass is aphanitic trending toward phaneritic, and both g'mass and phenos define a lineation. Zeolites, palagonite, and brown mineral Description Porphyritic w/ phaneritic g-mass in thin section w/ plag + px phenos in g'mass displaying hoziontal/sub-horizontal lineation that phenos almost all follow. Plag phenos show clear evidence of multi-stage histories. Textures 40% in g'mass; ~equigranular 200x40 µm, eu-subhedral laths; horizontal/sub-horiz lineation wraps around phenos; trachytic; 7% as phenos ranging from 200x500 µm to 2x2 mm; intricate zoning, sieve texture rims, and melt inclusions; many grains have relict resorption forms in interior Sub-to anhedral, elongate to equant; avg. ~20 x 80 µm with rounded corners common Sub-to anhedral, elongate to equant; avg. ~60 x 80 µm, max. 100 x 200 µm; 1 grain 360x 360 µm Eu-to subhedral; evenly dispersed; 80x80 µm max, avg. and majority 15 x 15 µm Anhedral w/ melt pockets and embayments; 1x1 mm to 400x400 µm basaltic-andesite N66°17.430' W22°23.347' 210 53.81 HFE1402/HfE2 dacite N66°14.795' W22°26.953' 225 63.92 HFE1403/HfE3 andesite N66°13.795' W22°30.269' 141 60.05 KIE1401/KlE1 rhyolite N66°06.788' W22°18.244' 104 74.77 KIE1402/KlE2 rhyolite N66°06.666' W22°18.090' 94 75.30 Sample 143Nd/ 144Nd ±2SE 145Nd/ 144Nd ±2SE 148Nd/ 144Nd ARE1301/ÁrE1 0.513027 0.000010 0.348418 0.000005 0.241565 ARE1302/ÁrE2 0.513031 0.000010 0.348425 0.000008 0.241567 ARE1303/ÁrE3 0.513011 0.000010 0.348414 0.000008 0.241562 ARE1304/ÁrE4 0.513023 0.000009 0.348423 0.000006 0.241587 KK-24 0.513055 0.000009 0.348406 0.000007 0.241564 HFE1402/HfE2 0.513042 0.000009 0.348422 0.000006 0.241579 HFE1403/HfE3 0.513041 0.000008 0.348428 0.000006 0.241576 Sample 176Hf/ 177Hf ±2SE 178Hf/ 177Hf ±2SE 180Hf/ 177Hf ARE1301/ÁrE1 0.283211 0.000008 1.467193 0.000012 1.886705 ARE1302/ÁrE2 0.283160 0.000003 1.467167 0.000006 1.886839 ARE1303/ÁrE3 0.283147 0.000003 1.467179 0.000005 1.886824 ARE1304/ÁrE4 0.283164 0.000003 1.467176 0.000005 1.886815 KK-24 0.283194 0.000008 1.467183 0.000014 1.886728 HFE1402/HfE2 0.283201 0.000007 1.467181 0.000012 1.886714 HFE1403/HfE3 0.283210 0.000007 1.467200 0.000014 1.886933 Sample 206 Pb/ 204 Pb ±2SE 207 Pb/ 204 Pb ±2SE 208 Pb/ 204 Pb ARE1301/ÁrE1 18.6503 0.0017 15.4820 0.0018 38.4134 ARE1302/ÁrE2 18.6440 0.0017 15.4840 0.0017 38.3555 ARE1303/ÁrE3 18.7812 0.0013 15.4915 0.0010 38.4787 ARE1304/ÁrE4 18.6357 0.0011 15.4779 0.0009 38.3407 HFE1402/HfE2 18.3531 0.0016 15.4718 0.0017 37.9617 HFE1403/HfE3 18.3348 0.0016 15.4699 0.0018 37.9533 Table S6G. Mass bias-corrected and normalized Pb isotope compositions measured via MC-ICP-MS at Washington State Univer Table S6E. Standard-corrected Nd isotope compositions measured via MC-ICP-MS at Washington State University. Table S6F. Standard-corrected Hf isotope compositions measured via MC-ICP-MS at Washington State University. lement and isotope compositions TiO2 Al2O3 FeO* MnO MgO CaO Na2O 0.327 13.42 3.99 0.078 0.27 1.79 5.21 3.013 14.62 12.24 0.228 3.96 7.79 3.70 0.539 14.45 3.87 0.146 0.41 1.92 5.47 0.192 12.83 2.30 0.073 0.10 1.11 5.34 0.187 13.00 1.84 0.055 0.08 1.18 4.99 0.944 14.32 5.35 0.110 1.57 3.92 4.53 0.36 13.66 2.94 0.04 0.17 0.95 5.66 0.32 13.01 3.67 0.03 0.23 0.62 5.49 0.34 13.80 2.38 0.03 0.10 0.82 5.73 Eu Gd Tb Dy Ho Er Tm 3.12 15.76 2.78 17.05 3.54 9.64 1.43 2.85 8.93 1.48 8.94 1.80 4.74 0.66 3.20 12.98 2.28 13.89 2.82 7.57 1.10 2.24 13.00 2.34 14.31 2.93 8.18 1.22 2.25 13.45 2.41 14.92 3.08 8.50 1.25 2.38 9.76 1.65 10.01 2.03 5.41 0.79 TiO2 Al2O3 FeO* MnO MgO CaO Na2O 0.30 15.68 5.17 0.14 0.23 3.46 5.69 TiO2 Al2O3 FeO* MnO MgO CaO Na2O wt % wt % wt % wt % wt % wt % wt % FUS-ICP FUS-ICP FUS-ICP FUS-ICP FUS-ICP FUS-ICP FUS-ICP n sections. Whole rock major and trace element abundances for Árnes (ArE) samples were determined using both XRF and ICPent data only from WSU. Sample KK-24 was analyzed via XRF at the College of Wooster. Precision for XRF analyses is better analyses is typically better than 5% (RSD) for the REEs and 10% for the remaining trace elements. In cases where XRF and ICPajor and trace elemental analyses on remaining Hrafnsfjörður (HfE) and Kaldalón (KlE) samples were carried out at ActLabs d LOI and pre-normalization sum (not including LOI) listed. Preparation for isotopic analysis is detailed in the manuscript. rsity. Major elements (reported in wt%) have been recalculated on a volatile-free basis and normalized to 100%. Trace ordinates use datum WGS84. ace elements are unnormalized and reported in ppm. ajor elements (reported in wt%) have been recalculated on a volatile-free basis and normalized to 100%. Trace elements are ed via a combination of methods as part of analytical package 4e-Research at Activation Laboratories. Major elements have lized. Standard analyses available by request. 15.01 13.49 0.21 3.56 7.16 3.63 0.65 15.49 8.86 0.24 0.26 4.47 4.91 1.31 14.81 10.15 0.18 2.43 5.54 4.04 0.91 12.90 3.33 0.04 0.12 1.45 4.90 2.21 12.13 3.75 0.07 0.23 1.51 4.63 2.06 ±2SE 150Nd/ 144Nd ±2SE εNd ±2SE 0.000007 0.236433 0.000025 7.6 0.2 0.000006 0.236395 0.000009 7.7 0.2 0.000006 0.236417 0.000009 7.3 0.2 0.000006 0.236433 0.000009 7.5 0.2 0.000008 0.236447 0.000010 8.1 0.2 0.000007 0.236432 0.000026 7.9 0.2 0.000006 0.236434 0.000021 7.9 0.2 ±2SE εHf ±2SE 0.000030 15.1 0.3 0.000011 13.3 0.1 0.000011 12.8 0.1 0.000009 13.4 0.1 0.000028 14.5 0.3 0.000033 14.7 0.3 0.000068 15.0 0.3 ±2SE 207 Pb/ 206 Pb ±2SE 208 Pb/ 206 Pb ±2SE 0.0045 0.8299 0.0017 2.0578 0.0075 0.0051 0.8305 0.0000 2.0573 0.0001 0.0025 0.8248 0.0000 2.0488 0.0001 0.0021 0.8306 0.0000 2.0574 0.0001 0.0048 0.8427 0.0017 2.0698 0.0075 0.0049 0.8435 0.0017 2.0713 0.0075 MS at Washington State University. n State University. State University. K2O P2O5 Total Original Sum Original LOI Sum w/LOI Ni 2.08 0.051 100.00 98.42 0.88 99.50 1 0.65 0.407 100.00 99.17 0.20 99.56 3 2.51 0.111 100.00 98.78 0.81 99.82 1 2.40 0.027 100.00 99.11 0.07 99.36 1 2.81 0.019 100.00 95.97 3.53 99.67 2 1.99 0.211 100.00 96.33 3.47 99.98 11 2.54 0.04 100.00 96.56 0 2.52 0.03 100.00 95.82 0 2.62 0.03 100.00 95.96 0 Yb Lu Ba Th Nb Y Hf Ta 9.14 1.41 324 7.23 48.09 89.49 14.43 3.27 3.97 0.61 135 2.53 28.61 44.77 6.31 1.95 6.87 1.03 388 9.01 60.19 72.32 15.93 4.13 7.74 1.16 363 8.37 51.16 75.95 11.78 3.64 7.83 1.19 353 8.28 49.21 79.43 11.38 3.59 4.89 0.77 288 6.73 36.78 51.97 11.29 2.64 K2O P2O5 Total Original Sum Original LOI Sum w/LOI Ni 1.56 0.06 100.00 6 K2O P2O5 Total Original Sum Original LOI Sum w/LOI Au wt % wt % ppb FUS-ICP FUS-ICP INAA d using both XRF and ICP-XRF analyses is better ases where XRF and ICPcarried out at ActLabs ed in the manuscript. d to 100%. Trace 00%. Trace elements are s. Major elements have 2.20 0.29 100.00 99.22 0.98 100.20 0.42 0.11 100.00 97.92 0.94 98.86 1.64 0.24 100.00 95.28 5.32 100.60 0.26 0.02 100.00 96.56 2.03 98.59 0.26 0.05 100.00 97.15 2.25 99.40 Cr Sc V Ba Rb Sr Zr Y Nb 2 10 7 323 42 140 556 94 49.5 0 28 274 144 10 297 252 45 30.6 3 7 20 382 50 159 614 75 62.1 3 6 6 359 50 77 381 80 52.6 3 4 2 351 52 74 364 85 49.6 17 11 66 287 42 190 436 54 37.6 2.4 6.5 0 406.4 50.2 162.3 721.3 59.4 84.8 1 3.7 0.4 401.1 48.7 140.1 731.8 79.2 86.5 1.9 6.5 0 408.9 50.8 158.1 736 56.9 86.4 U Pb Rb Cs Sr Sc Zr 2.03 4.58 41.1 0.22 142 9.5 568 0.67 1.80 8.9 0.06 300 28.8 249 2.27 5.43 48.0 0.19 160 6.0 621 1.94 4.86 49.5 0.31 78 5.4 390 2.19 5.74 51.5 0.53 77 4.6 372 1.87 4.43 41.1 0.43 191 11.2 433 Cr Sc V Ba Rb Sr Zr Y Nb 11 1 288 32 162 651 123 37 Ag As Ba Be Bi Br Cd Co Cr ppm ppm ppm ppm ppm ppm ppm ppm ppm MULT INAA / TD-ICP INAA FUS-ICP FUS-ICP FUS-MS INAA TD-ICP INAA INAA < 0.5 < 1 140 2 < 0.1 < 0.5 < 0.5 38.8 12.1 < 0.5 1 262 3 < 0.1 < 0.5 < 0.5 3.6 < 0.5 < 0.5 < 1 208 2 < 0.1 < 0.5 < 0.5 27.8 21.7 1.2 < 1 336 3 < 0.1 < 0.5 < 0.5 < 0.1 16.8 1.3 1 326 3 0.1 < 0.5 < 0.5 < 0.1 30.1 Ga Cu Zn Pb La Ce Th Nd U 23 10 129 5 61 101 7 61 3 23 34 139 2 28 59 3 33 1 27 18 111 6 61 128 10 54 2 24 8 99 5 56 125 8 54 2 23 15 95 6 58 121 9 55 2 21 39 89 4 48 95 6 46 2 29.3 1.7 177 5.3 83.6 126.9 9.4 81.4 2.2 29.7 2.2 237.2 6.8 111.5 113.2 10.1 102.1 2 29.3 1.9 193.5 5.8 55 125.6 11.2 57.4 1.6 Ga Cu Zn Pb La Ce Th Nd U 20 170 5 67 Cs Cu Ga Ge Hf Hg In Ir Mo ppm ppm ppm ppm ppm ppm ppm ppb ppm FUS-MS TD-ICP FUS-MS FUS-MS FUS-MS INAA FUS-MS INAA FUS-MS 0.1 86 22 1.5 4 < 1 0.1 < 1 < 0.1 17 27 2 17.3 < 1 0.3 < 1 0.2 42 22 1.5 6.9 < 1 0.1 < 1 0.5 18 21 1.7 9 < 1 0.2 < 1 0.3 26 21 1.5 10.8 < 1 0.1 < 1 Sum TE Sum (%) ME+TE If Fe3+ 1622 0.16 98.58 99.94 1406 0.14 99.31 100.91 1790 0.18 98.96 100.24 1397 0.14 99.25 99.61 1370 0.14 96.11 99.87 1504 0.15 96.48 100.56 Nb Ni Pb Rb S Sb Sc Se Sn ppm ppm ppm ppm % ppm ppm ppm ppm FUS-MS TD-ICP TD-ICP FUS-MS TD-ICP INAA INAA INAA FUS-MS 12.7 19 < 5 13 0.028 < 0.1 26.7 < 0.5 25.4 1 < 5 24 0.02 < 0.1 19.2 < 0.5 14.6 10 < 5 20 0.022 0.2 19.5 < 0.5 21.3 1 < 5 50 0.007 0.2 6.97 < 0.5 20.7 2 < 5 42 0.007 < 0.1 6.81 < 0.5 Sr Ta Th U V W Y Zn Zr ppm ppm ppm ppm ppm ppm ppm ppm ppm FUS-ICP FUS-MS FUS-MS FUS-MS FUS-ICP INAA FUS-ICP MULT INAA / TD-ICP FUS-ICP 0.93 1.69 0.55 248 < 1 49 130 176 1.76 4.22 1.39 5 < 1 106 220 180 1.04 3.08 0.95 155 < 1 71 120 71 2.1 6.02 1.75 10 < 1 88 97 72 1.97 5.72 1.78 10 < 1 95 99 La Ce Pr Nd Sm Eu Gd Tb Dy ppm ppm ppm ppm ppm ppm ppm ppm ppm FUS-MS FUS-MS FUS-MS FUS-MS FUS-MS FUS-MS FUS-MS FUS-MS FUS-MS 17.5 40.7 5.6 26.1 7.35 2.62 8.38 1.56 9.74 50.3 115 14.9 64.8 16.1 4 16 2.94 18.8 28.3 61.5 8.4 37 9.86 2.69 10.8 1.99 12.3 41.5 89.5 11.6 48 11.7 2.35 12.1 2.34 15.2 44.1 94.2 12 50.7 12.5 2.32 13.6 2.52 16.3 Ho Er Tl Tm Yb Lu ppm ppm ppm ppm ppm ppm FUS-MS FUS-MS FUS-MS FUS-MS FUS-MS FUS-MS 1.86 5.39 < 0.05 0.779 5.02 0.814 3.93 11.7 < 0.05 1.75 12.1 1.97 2.5 7.22 < 0.05 1.07 7.01 1.12 3.08 9.57 0.08 1.39 9.45 1.45 3.4 10.3 0.15 1.56 10.5 1.65 Supplemental Table S7. Oxygen isotope modeling d 18 O 1 * mass fraction 1 + d 18 O 2 * mass fraction 2 where 1 and 2 refer to the two end members. To model δ 18 O of evolving melts, the measurable fractionation of oxygen isotopes among equilibrated phases must be taken into account. Specifically: In the models below, we assume the following: Relative d 18 O of phases: (1) δ 18 O of melt from which zircon grew ~= d 18 O zircon + 1.8‰ (2) δ 18 O of rhyolite formed by closed system fractional crystallization of basaltic magma ~= δ 18 O basaltic magma + 0.5‰ (3) δ 18 O of rhyolite formed by anatexis of altered basalt ~= δ 18 O basalt + 0.5‰ d 18 O of end members and average Westfjords melt: Example Mixing Calculations *= d 18 O mixed melt +0.5 *= d 18 O mixed melt +0.5 5.5 1 2 0 6.0 4.2 5 1 5.5 0.9 2 0.1 5.7 3.9 Possible 5 0.9 5.5 0.8 2 0.2 5.3 3.5 Westfjords 5 0.8 Possible 5.5 0.7 2 0.3 5.0 3.2 5 0.7 Westfjords 5.5 0.6 2 0.4 4.6 2.8 5 0.6 5.5 0.5 2 0.5 4.3 2.5 5 0.5 (3) Altered crust: δ 18 O = -10 to +2‰ (Hattori and Muehlenbachs 1982)
Our simple modeling is aimed at constraining mass fractions of two end members in rhyolitic melt. We assume that the mass fraction of oxygen in each of two end member melts is identical, and th
(1) δ 18 O zircon is substantially lower than δ 18 O in melt from which it grows; for rhyolitic melt, the difference is roughly 1.8‰ (Bindemanet al., 2012, Trail et al. 2009).
(2) Melt has higher δ 18 O than the bulk crystallizing assemblage; current estimates are that extended closed-system crystallization of mafic magma melt leads to an increase of roughly half a unit to d 18 O new mantle magma fraction new mantle magma d 18 O altered crust fraction of altered crust *resulting mixed melt #zircon d 18 O d 18 O new mantle magma fraction new mantle magma 5.5 0.4 2 0.6 3.9 2.1 0.4 5.5 0.3 2 0.7 3.6 1.8 0.3 5.5 0.2 2 0.8 3.2 1.4 0.2 5.5 0.1 2 0.9 2.9 1.1 0.1 5.5 0 2 1 2.5 0.7 0 5.5 1 0 0 6.0 4.2 1 5.5 0.9 0 0.1 5.5 3.7 Possible 0.92 Possible 5.5 0.8 0 0.2 4.9 3.1 Westfjords 0.8 Westfjords 5.5 0.7 0 0.3 4.4 2.6 0.7 5.5 0.6 0 0.4 3.8 2.0 0.6 5.5 0.5 0 0.5 3.3 1.5 0.5 5.5 0.4 0 0.6 2.7 0.9 0.4 5.5 0.3 0 0.7 2.2 0.4 0.3 5.5 0.2 0 0.8 1.6 -0.2 0.2 5.5 0.1 0 0.9 1.1 -0.8 0.1 5.5 0 0 1 0.5 -1.3 0 5.5 1 -4 0 6.0 4.2 Possible 1 Possible 5.5 0.9 -4 0.1 5.1 3.3 Westfjords 0.9 Westfjords 5.5 0.8 -4 0.2 4.1 2.3 0.8 5.5 0.7 -4 0.3 3.2 1.4 0.7 5.5 0.6 -4 0.4 2.2 0.4 0.6 5.5 0.5 -4 0.5 1.3 -0.6 0.5 5.5 0.4 -4 0.6 0.3 -1.5 0.4 5.5 0.3 -4 0.7 -0.7 -2.5 0.3 5.5 0.2 -4 0.8 -1.6 -3.4 0.2 5.5 0.1 -4 0.9 -2.6 -4.4 0.1 5.5 0 -4 1 -3.5 -5.3 0 Possible 5.5 1 -10 0 6.0 4.2 Possible 1 Westfjords 5.5 0.9 -10 0.1 4.5 2.7 Westfjords 0.985 5.5 0.8 -10 0.2 2.9 1.1 0.8 5.5 0.7 -10 0.3 1.4 -0.5 0.7 5.5 0.6 -10 0.4 -0.2 -2.0 0.6 5.5 0.5 -10 0.5 -1.8 -3.6 0.5 5.5 0.4 -10 0.6 -3.3 -5.1 0.4 5.5 0.3 -10 0.7 -4.9 -6.7 0.3 5.5 0.2 -10 0.8 -6.4 -8.2 0.2 5.5 0.1 -10 0.9 -8.0 -9.8 0.1 5.5 0 -10 1 -9.5 -11.3 0 *= d 18 O mixed melt +0.5 *= d 18 O mixed melt +0.5 *= d 18 O mixed melt +0.5 2 0 5.5 3.7 4 1 2 0 4.5 2 0.1 5.2 3.4 Possible 4 0.9 2 0.1 4.3 2 0.2 4.9 3.1 Westfjords 4 0.8 2 0.2 4.1 2 0.3 4.6 2.8 (KlE samples) 4 0.7 2 0.3 3.9 2 0.4 4.3 2.5 4 0.6 2 0.4 3.7 2 0.5 4.0 2.2 4 0.5 2 0.5 3.5 ntical, and therefore that d 18 O of the mixture = half a unit to a unit in d 18 O in fractionated rhyolite melt (e.g. Bindeman 2008; Trail et al. 2009; cf. Valley et al. 2005). d 18 O altered crust fraction of altered crust resulting mixed melt d 18 O d 18 O altered crust fraction of altered crust resulting mixed melt d 18 O zircon d 18 O d 18 O new mantle magma fraction new mantle magma 0.6 3.7 1.9 4 0.4 0.6 3.3 2 0.7 3.4 1.6 4 0.3 0.7 3.1 2 0.8 3.1 1.3 4 0.2 0.8 2.9 2 0.9 2.8 1.0 4 0.1 0.9 2.7 2 1 2.5 0.7 4 0 1 2.5 0 0 5.5 3.7 0 0.08 5.1 3.3 0 0.2 4.5 2.7 0 0.3 4.0 2.2 0 0.4 3.5 1.7 0 0.5 3.0 1.2 0 0.6 2.5 0.7 0 0.7 2.0 0.2 0 0.8 1.5 -0.3 0 0.9 1.0 -0.8 0 1 0.5 -1.3 -4 0 5.5 3.7 -4 0.1 4.6 2.8 -4 0.2 3.7 1.9 -4 0.3 2.8 1.0 -4 0.4 1.9 0.1 -4 0.5 1.0 -0.8 -4 0.6 0.1 -1.7 -4 0.7 -0.8 -2.6 -4 0.8 -1.7 -3.5 -4 0.9 -2.6 -4.4 -4 1 -3.5 -5.3 -10 0 5.5 3.7 -10 0.015 5.3 3.5 -10 0.2 2.5 0.7 -10 0.3 1.0 -0.8 -10 0.4 -0.5 -2.3 -10 0.5 -2.0 -3.8 -10 0.6 -3.5 -5.3 -10 0.7 -5.0 -6.8 -10 0.8 -6.5 -8.3 -10 0.9 -8.0 -9.8 -10 1 -9.5 -11.3 *= d 18 O mixed melt +0.5 2.7 2.5 2.3 2.1 1.9 1.7 zircon d 18 O 1.5 1.3 1.1 0.9 0.7 Table S8. Zircon Hf isotope methods and standards Standards used for Árnes zircon, unit Tr1, analyses: Sample 176 Hf/ 177 Hf 2SE 176 Lu/ 177 Hf 2SE 176 Yb/ 177 Hf 2SE Mud Tank-1 0.282497 0.000027 0.00003 0.00000 0.0009 0.0000 Mud Tank-2 0.282516 0.000024 0.00003 0.00000 0.0008 0.0000 MunZirc4-1 0.282114 0.000041 0.01007 0.00001 0.1890 0.0002 MunZirc4-2 0.282117 0.000044 0.00956 0.00029 0.1800 0.0060 MunZirc4-3 0.282124 0.000044 0.00743 0.00075 0.1370 0.0150 R33-1 0.282718 0.000029 0.00171 0.00004 0.0437 0.0013 R33-2 0.282735 0.000023 0.00224 0.00011 0.0578 0.0030 R33-3 0.282746 0.000024 0.00166 0.00009 0.0407 0.0026 Standards used for Árnes zircon, units Tr2, Tr3, Tr4 analyses: Sample 176 Hf/ 177 Hf 2SE 176 Lu/ 177 Hf 2SE 176 Yb/ 177 Hf 2SE MunZirc4-1 0.282146 0.000038 0.01236 0.00022 0.2491 0.0060 MunZirc4-2 0.282141 0.000046 0.00560 0.00100 0.1090 0.0230 MunZirc4-3 0.282118 0.000035 0.01271 0.00037 0.2582 0.0072 MunZirc4-4 0.282121 0.000046 0.01000 0.00011 0.2002 0.0023 MunZirc4-5 0.282138 0.000030 0.00923 0.00005 0.1821 0.0013 MunZirc4-6 0.282125 0.000034 0.00886 0.00014 0.1739 0.0030 MunZirc4-7 0.282122 0.000037 0.00999 0.00010 0.1982 0.0021 MunZirc4-8 0.282128 0.000041 0.00568 0.00041 0.1090 0.0100 MunZirc4-9 0.282124 0.000035 0.00974 0.00061 0.1900 0.0130 MunZirc4-10 0.282127 0.000032 0.00978 0.00008 0.1908 0.0018 MunZirc4-11 0.282132 0.000029 0.01182 0.00014 0.2353 0.0027 MunZirc4-12 0.282134 0.000051 0.00503 0.00022 0.0957 0.0049 MunZirc4-13 0.282143 0.000027 0.00907 0.00006 0.1767 0.0014 MunZirc4-14 0.282045 0.000190 0.01050 0.00570 0.2600 0.1700 For the Árnes sample analyses, we used Mud Tank ( 176 Hf/ 177 Hf = 0.282507 ± 6; Woodhead and Hergt, 2005) to normalize secondary standards Temora-2 ( 176 Hf/ 177 Hf =0.282686 ± 8; Woodhead and Hergt, 2005) and R33 ( 176 Hf/ 177 Hf =0.282764 ± were interspersed with unknowns to assess accuracy and external reproducibility. Given the narrow range of Hf isotope c for the isobaric interference of Wiedenbeck et al., 1995) as secondar ICPMS determination of the isotope composition of purified Hf from these zircons.
Note on Error Propagation: 99% of the error correction are done internally using stable Hf and Yb ratios, so there is no nee a std (like Mud Tank), and that could be propagated. However, that yields such a small correction that it barely adds to th mean calculation of the various standards yields MSWD values less than 1 almost all of the time, suggesting that there a
GJ1-1 0.281996 0.000033 0.00024 0.00000 0.0058 0.0000 GJ1-2 0.282021 0.000035 0.00024 0.00000 0.0058 0.0000 GJ1-3 0.281974 0.000038 0.00024 0.00000 0.0058 0.0000 GJ1-4 0.282009 0.000039 0.00024 0.00000 0.0058 0.0000 GJ1-5 0.281983 0.000040 0.00024 0.00000 0.0056 0.0000 GJ1-6 0.282016 0.000027 0.00024 0.00000 0.0056 0.0000 GJ1-7 0.281990 0.000036 0.00024 0.00000 0.0058 0.0000 GJ1-8 0.282022 0.000029 0.00024 0.00000 0.0058 0.0000 GJ1-9 0.282009 0.000038 0.00024 0.00000 0.0059 0.0000 GJ1-10 0.281978 0.000035 0.00024 0.00000 0.0059 0.0000 GJ1-11 0.282018 0.000035 0.00024 0.00000 0.0058 0.0000 GJ1-12 0.281988 0.000034 0.00024 0.00000 0.0057 0.0000 GJ1-13 0.282001 0.000031 0.00024 0.00000 0.0057 0.0000 GJ1-15 0.282006 0.000038 0.00024 0.00000 0.0057 0.0000 GJ1-16 0.282012 0.000037 0.00024 0.00000 0.0057 0.0000 Mud Tank-1 0.282527 0.000034 0.00002 0.00000 0.0007 0.0000 Mud Tank-2 0.282495 0.000022 0.00002 0.00000 0.0008 0.0001 Mud Tank-3 0.282492 0.000023 0.00002 0.00000 0.0006 0.0000 Mud Tank-4 0.282496 0.000024 0.00002 0.00000 0.0006 0.0000 Mud Tank-5 0.282499 0.000019 0.00003 0.00000 0.0009 0.0000 Mud Tank-6 0.282506 0.000025 0.00002 0.00000 0.0006 0.0000 Mud Tank-7 0.282508 0.000020 0.00002 0.00000 0.0008 0.0001 Mud Tank-8 0.282506 0.000021 0.00002 0.00000 0.0006 0.0000 Mud Tank-9 0.282506 0.000025 0.00002 0.00000 0.0006 0.0000 Mud Tank-10 0.282506 0.000024 0.00002 0.00000 0.0006 0.0000 Mud Tank-11 0.282527 0.000024 0.00002 0.00000 0.0005 0.0000 Mud Tank-12 0.282522 0.000023 0.00002 0.00000 0.0005 0.0000 Mud Tank-13 0.282510 0.000019 0.00002 0.00000 0.0006 0.0000 Mud Tank-14 0.282503 0.000028 0.00003 0.00000 0.0008 0.0000 Mud Tank-15 0.282508 0.000022 0.00002 0.00000 0.0005 0.0000 Mud Tank-16 0.282488 0.000016 0.00003 0.00000 0.0008 0.0000 Mud Tank-17 0.282497 0.000020 0.00003 0.00000 0.0008 0.0000 Mud Tank-18 0.282503 0.000025 0.00002 0.00000 0.0005 0.0000 Mud Tank-19 0.282503 0.000029 0.00002 0.00000 0.0005 0.0000 Mud Tank-20 0.282517 0.000020 0.00002 0.00000 0.0006 0.0000 Mud Tank-21 0.282515 0.000022 0.00002 0.00000 0.0005 0.0000 Mud Tank-22 0.282506 0.000029 0.00002 0.00000 0.0005 0.0000 Mud Tank-23 0.282510 0.000030 0.00001 0.00000 0.0003 0.0000 Mud Tank-24 0.282506 0.000027 0.00001 0.00000 0.0003 0.0000 Mud Tank-25 0.282508 0.000023 0.00001 0.00000 0.0002 0.0000 R33-1 0.282687 0.000032 0.00101 0.00005 0.0260 0.0015 R33-2 0.282672 0.000040 0.00112 0.00005 0.0292 0.0016 R33-4 0.282734 0.000040 0.00143 0.00004 0.0364 0.0011 R33_3.FIN_ 0.282728 0.000034 0.00194 0.00002 0.0512 0.0007 R33-5 0.282748 0.000021 0.00131 0.00004 0.0343 0.0012 R33-7 0.282756 0.000027 0.00239 0.00002 0.0633 0.0006 R33-8 0.282724 0.000024 0.00157 0.00006 0.0408 0.0015 R33-9 0.282757 0.000022 0.00201 0.00005 0.0529 0.0019 R33-10 0.282759 0.000024 0.00170 0.00004 0.0439 0.0010 R33-11 0.282797 0.000042 0.00093 0.00013 0.0259 0.0039 R33-12 0.282718 0.000023 0.00181 0.00009 0.0496 0.0024 R33-13 0.282755 0.000028 0.00214 0.00007 0.0571 0.0023 R33-14 0.282688 0.000029 0.00202 0.00008 0.0540 0.0022 R33-15 0.282732 0.000031 0.00220 0.00008 0.0611 0.0026 R33-16 0.282720 0.000026 0.00144 0.00004 0.0396 0.0013 R33-17 0.282767 0.000028 0.00262 0.00001 0.0772 0.0006 R33-18 0.282715 0.000022 0.00180 0.00005 0.0488 0.0013 0.282733 Temora2_1.FIN_ 0.282603 0.000060 0.00093 0.00001 0.0233 0.0001 Temora2_2.FIN_ 0.282654 0.000027 0.00091 0.00001 0.0224 0.0003 Temora2_3.FIN_ 0.282646 0.000036 0.00051 0.00000 0.0127 0.0001 Temora2_4.FIN_ 0.282677 0.000056 0.00080 0.00001 0.0199 0.0003 Standards used for HfE and KlE zircon analyses: Sample 176 Hf/ 177 Hf 2SE 176 Lu/ 177 Hf 2SE 176 Yb/ 177 Hf 2SE MUNZirc2-1 0.282131 0.000028 0.002170 0.000130 0.066500 0.003300 MUNZirc2-2 0.282151 0.000023 0.003122 0.000087 0.100570 0.000570 MUNZirc2-3 0.282140 0.000025 0.001713 0.000009 0.054200 0.001700 MUNZirc2-4 0.282142 0.000024 0.001727 0.000011 0.055100 0.001700 MUNZirc4-1 0.282170 0.000037 0.011288 0.000034 0.330900 0.009700 MUNZirc4-2 0.282115 0.000036 0.011519 0.000090 0.327700 0.006300 MUNZirc4-3 0.282117 0.000035 0.011970 0.000110 0.344000 0.006100 MUNZirc4-4 0.282148 0.000042 0.012360 0.000200 0.357400 0.003900 0.282060 0.282080 0.282100 0.282120 0.282140 0.282160 0.282180 0.282200 0.282220 0 1 2 3 4 5 6 7 8 9 Std corr. 176Hf/177Hf MUNZirc StdCorrected R33-1 0.282765 0.000024 0.001815 0.000036 0.070240 0.000860 R33-2 0.282737 0.000027 0.001793 0.000035 0.071300 0.002500 R33-3 0.282746 0.000030 0.002018 0.000012 0.079700 0.002300 R33-4 0.282720 0.000022 0.001090 0.000035 0.040550 0.000450 R33-5 0.282737 0.000025 0.001547 0.000045 0.059100 0.004800 R33-6 0.282756 0.000027 0.002129 0.000017 0.085200 0.003700 R33-7 0.282764 0.000025 0.001272 0.000018 0.050000 0.001200 R33-8 0.282739 0.000029 0.001952 0.000022 0.080600 0.002300 R33-9 0.282753 0.000033 0.001831 0.000018 0.076300 0.002200 R33-10 0.282783 0.000034 0.004401 0.000092 0.178000 0.010000 FC1-1 0.282170 0.000027 0.001400 0.000004 0.058000 0.001700 FC1-2 0.282199 0.000030 0.001280 0.000003 0.053300 0.001600 FC1-3 0.282177 0.000026 0.001215 0.000015 0.050400 0.002200 FC1-5 0.282174 0.000024 0.000951 0.000011 0.039300 0.000700 FC1-6 0.282201 0.000033 0.001208 0.000007 0.053300 0.001500 FC1-7 0.282196 0.000026 0.001176 0.000010 0.049600 0.001200 FC1-8 0.282190 0.000027 0.001053 0.000014 0.044000 0.000890 FC1-9 0.282185 0.000024 0.000941 0.000017 0.037830 0.000400 FC1-10 0.282187 0.000035 0.000866 0.000006 0.037700 0.001800 FC1-11 0.282178 0.000023 0.001295 0.000004 0.055100 0.001600 Plesovice-1 0.282483 0.000019 0.000096 0.000002 0.005540 0.000120 Plesovice-2 0.282489 0.000020 0.000095 0.000002 0.005440 0.000110 Plesovice-3 0.282495 0.000020 0.000093 0.000001 0.005340 0.000110 Plesovice-4 0.282482 0.000022 0.000092 0.000001 0.005270 0.000110 Plesovice-5 0.282481 0.000020 0.000095 0.000002 0.005410 0.000110 Plesovice-6 0.282470 0.000018 0.000093 0.000001 0.005310 0.000110 Plesovice-7 0.282497 0.000020 0.000092 0.000001 0.005240 0.000110 Plesovice-8 0.282477 0.000019 0.000091 0.000001 0.005260 0.000110 Plesovice-9 0.282468 0.000021 0.000092 0.000001 0.005250 0.000110 Plesovice-10 0.282482 0.000018 0.000090 0.000001 0.005190 0.000100 Plesovice-11 0.282482 0.000022 0.000093 0.000001 0.005330 0.000120 Plesovice-12 0.282473 0.000027 0.000091 0.000001 0.005210 0.000110 Plesovice-13 0.282464 0.000024 0.000090 0.000001 0.005140 0.000120 Plesovice-14 0.282477 0.000019 0.000091 0.000001 0.005170 0.000100 Plesovice-15 0.282485 0.000018 0.000093 0.000002 0.005280 0.000093 Plesovice-16 0.282460 0.000021 0.000092 0.000002 0.005230 0.000110 Plesovice-17 0.282489 0.000020 0.000091 0.000001 0.005210 0.000120 Plesovice-18 0.282492 0.000024 0.000093 0.000002 0.005307 0.000094 Plesovice-19 0.282489 0.000022 0.000092 0.000002 0.005280 0.000100 Plesovice-20 0.282496 0.000021 0.000094 0.000002 0.005350 0.000100 Plesovice-21 0.282492 0.000016 0.000093 0.000002 0.005333 0.000094 91500-1 0.282310 0.000032 0.000292 0.000001 0.011200 0.000360 91500-2 0.282304 0.000043 0.000293 0.000001 0.011170 0.000390 91500-3 0.282302 0.000034 0.000292 0.000001 0.011120 0.000360 91500-4 0.282283 0.000030 0.000293 0.000001 0.011050 0.000340 91500-5 0.282297 0.000033 0.000291 0.000001 0.011090 0.000340 91500-6 0.282294 0.000029 0.000289 0.000001 0.011050 0.000320 91500-8 0.282298 0.000035 0.000290 0.000001 0.011410 0.000370 91500-9 0.282295 0.000035 0.000288 0.000001 0.010940 0.000320 91500-11 0.282290 0.000030 0.000292 0.000001 0.010990 0.000320 178 Hf/ 177 Hf 2SE 180 Hf/ 177 Hf 2SE Total Hf Duration 1.467274 0.000041 1.886790 0.000110 16.0 46 1.467226 0.000043 1.886783 0.000089 15.5 46 1.467218 0.000041 1.886756 0.000091 16.3 46 1.467288 0.000047 1.886728 0.000083 16.7 46 1.467244 0.000038 1.886719 0.000075 16.2 46 1.467245 0.000035 1.886790 0.000100 16.7 46 1.467270 0.000046 1.886770 0.000097 16.4 46 1.467230 0.000038 1.886810 0.000099 16.2 46 9 0.282680 0.282700 0.282720 0.282740 0.282760 0.282780 0.282800 0.282820 0.282840 0 2 4 6 8 10 12 Std corr. 176Hf/177Hf R33 StdCorrected 0.282120 0.282140 0.282160 0.282180 0.282200 0.282220 0.282240 0 Std corr. 176Hf/177Hf 0.282460 0.282470 0.282480 0.282490 0.282500 0.282510 0.282520 0.282530 Std corr. 176Hf/177Hf 0.282600 0.282650 0.282700 0.282750 0 2 4 6 8 10 0.282500 0.282550 0.282600 0.282650 0.282700 0.282750 0 0.5 1 1.5 2 2.5 Temora2 Std. Corrected 1.467275 0.000037 1.886832 0.000095 14.0 46 1.467302 0.000047 1.886860 0.000110 13.0 46 1.467216 0.000043 1.886827 0.000082 12.8 46 1.467263 0.000038 1.886811 0.000068 15.1 46 1.467240 0.000044 1.886720 0.000110 13.8 46 1.467270 0.000044 1.886800 0.000110 13.1 46 1.467260 0.000039 1.886776 0.000088 14.1 46 1.467236 0.000041 1.886743 0.000095 12.3 46 1.467245 0.000042 1.886886 0.000090 12.1 46 1.467268 0.000041 1.886780 0.000100 14.1 46 1.467278 0.000040 1.886930 0.000100 11.9 46 1.467252 0.000045 1.886800 0.000100 11.7 46 1.467291 0.000048 1.886810 0.000100 11.7 46 1.467237 0.000046 1.886790 0.000088 11.2 46 1.467283 0.000059 1.886770 0.000150 12.8 26 1.467232 0.000040 1.886793 0.000091 11.9 46 1.467245 0.000045 1.886770 0.000100 12.0 46 1.467294 0.000049 1.886780 0.000095 12.4 46 1.467248 0.000046 1.886680 0.000120 13.2 30 1.467209 0.000049 1.886790 0.000100 12.2 41 1.467283 0.000039 1.886810 0.000110 14.7 46 1.467258 0.000041 1.886832 0.000087 14.6 46 1.467274 0.000046 1.886834 0.000089 14.6 46 1.467282 0.000049 1.886840 0.000130 14.6 46 1.467272 0.000048 1.886820 0.000110 14.8 46 1.467258 0.000046 1.886785 0.000089 14.9 44 1.467261 0.000037 1.886767 0.000070 14.3 46 1.467249 0.000041 1.886850 0.000110 14.5 46 1.467255 0.000029 1.886843 0.000084 14.5 46 1.467295 0.000041 1.886829 0.000087 14.4 46 1.467276 0.000052 1.886807 0.000070 14.8 46 1.467277 0.000035 1.886831 0.000098 14.7 46 1.467261 0.000043 1.886882 0.000098 14.8 46 1.467260 0.000049 1.886876 0.000092 14.4 43 1.467283 0.000039 1.886780 0.000085 14.8 46 1.467245 0.000042 1.886800 0.000100 14.9 43 1.467257 0.000042 1.886785 0.000095 14.9 46 1.467274 0.000039 1.886790 0.000110 14.9 46 1.467237 0.000045 1.886770 0.000110 14.7 46 1.467286 0.000046 1.886801 0.000090 15.0 46 1.467259 0.000041 1.886795 0.000097 14.4 46 1.467279 0.000065 1.886830 0.000110 7.3 46 1.467237 0.000055 1.886780 0.000140 7.3 46 1.467244 0.000056 1.886790 0.000150 7.1 46 0.282430 0.282440 0.282450 0.282460 0.282470 0 Std corr. 176Hf/177H 0.282240 0.282260 0.282280 0.282300 0.282320 0.282340 0.282360 0 1 Std corr. 176Hf/177Hf 1.467178 0.000056 1.886700 0.000130 7.3 46 1.467273 0.000060 1.886810 0.000150 7.1 46 1.467247 0.000061 1.886860 0.000120 7.1 46 1.467255 0.000052 1.886820 0.000140 7.8 34 1.467274 0.000058 1.886820 0.000140 7.2 46 1.467304 0.000050 1.886820 0.000120 7.5 46 zircon doped with hafnium and rare earth elements: A reference material for in situ hafnium isotope he "laser ablation split stream" method. Geochemistry, Geophysics, Geosystems, 15(1). ural standard for U-Pb and Hf isotopic microanalysis. Chemical Geology, 249(1-2), 1-35. for U-Th-Pb, Lu-Hf, Trace Element and REE Analyses. Geostandards and Geoanalytical Research, 19(1), 1itu Hf Isotope Determination. Geostandards and Geoanalytical Research, 29(2), 183-195. 5 6 7 8 9 nit analyses only) 10 12 14 16 ted 10 12 14 16 ed 20 25 30 ected ted 2 4 6 8 10 12 FC1 StdCorrected Plesovice StdCorrected