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1. Constraining Halogen Budgets in Continental Arcs at the Whole-Rock Scale

   Bucheli, César; Segee-Wright, George; Grabiec, Justine G; Cooperdock, Emily HG; Barnes, Jaime D; Lackey, Jade Star; Stockli, Lisa D; Stockli, Daniel F; Ardill, Katie (June 2024, 2024 V.M. Goldschmidt Conference Abstracts)

   Halogens (F, Cl, Br, I) are primary components of volcanic gas emissions and play an essential role in continental arc magmatic environments due to their solubility in fluids that generate metallic ore deposits. Despite their ubiquity, the behavior and budget of halogens in continental arc environments are poorly constrained. We investigated the plutonic and volcanic halogen budgets in intermediate-to-felsic igneous rocks (56–77 wt% SiO2) from the Sierra Nevada (California) - a Mesozoic continental arc where plutonic and volcanic outcrops can be correlated via their geographic, compositional, and geochronologic framework. We measured the halogen concentrations of bulk rock powders and their leachates via ion chromatography (F, Cl) and ICP-MS (Br, I). Halogen concentrations in our rock powders range between 107–727 μg/g F, 13–316 μg/g Cl, 2–323 ng/g Br, and 1–69 ng/g I. In contrast, leachates yielded 3–4 orders of magnitude less Cl and F, one order of magnitude less I, and similar amounts of Br compared to their corresponding bulk rocks. Preliminary data show no significant differences between volcanic and plutonic samples, suggesting that halogen concentrations in these rocks are insensitive to shallow fractionation. Although F and I exhibit no correlation with major element compositions, Cl and Br display negative trends with increasing SiO2 and K2O, and positive trends with increasing Fe2O3T, MnO, MgO, CaO, and TiO2, suggesting mafic minerals as important hosts of structurally bound halogens. Overall, Sierran plutonic rocks display low halogen contents (max. F, Cl = 727, 315 μg/g), consistent with biotite- and apatite-bearing granitoids reported in [1]. This work suggests that halogens do not preferentially enrich in shallow plutonic or volcanic portions of a continental arc system and that mafic mineral phases likely serve as primary reservoirs of these elements in intermediate-to-felsic igneous rocks. These hypotheses will be further investigated in future work through in-situ analysis of halogen concentrations in crystals. [1] Teiber, Marks, Wenzel, Siebel, Altherr & Markl (2014), Chemical Geology, vol. 374–375, pp. 92–109, doi: 10.1016/j.chemgeo.2014.03.006 

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2. Changes in andesite-dacite genesis over the 3-Myr lifespan of the Goat Rocks volcanic complex, central Cascade arc

   Wall, K.T.; Grunder, A.L (October 2019, American Geophysical Union)

   Documentation and interpretation of changes in composition and volume of magmas at the Goat Rocks Volcanic Complex, southwest Washington 

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3. Thermal Evolution of the 3 Ma to 0.1 Ma Goat Rocks Volcanic Complex, Washington Cascades

   Wall, K.T.; Grunder, A.L. (October 2021, American Geophysical Union)

   Interpretation of magma storage temperature in time at the Goat Rocks Volcanic Complex SW Washington Cascades 

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4. Origin and Evolution of Miocene Basanite to Comendite Lavas at the Mount Overlord Volcanic Field, Northern Victoria Land, Antarctica

   https://doi.org/10.1093/petrology/egaf014  

   Kim, Jihyuk; Kyle, Philip R; Lee, Mi Jung; Lee, Jong Ik; Heizler, Matthew; Im, Sunghwan; Gamble, John A; Noll, Mark R (March 2025, Journal of Petrology)

   Troll, Valentin (Ed.)

   Continental alkaline magmatism produces a wide variety of igneous rock types because of varying degrees of partial melting of heterogenous mantle sources, fractional crystallization, and magma contamination during transit through the continental crust. The Mount Overlord Volcanic Field (MOVF) is a continental alkaline volcanic province in northern Victoria Land, Antarctica. Mount Overlord and the associated vents that make up the volcanic field are some of the least-explored volcanic rocks in the western Ross Sea. The MOVF sits within the Transantarctic Mountains, which form the rift shoulder of the extensive West Antarctic Rift System. The compositions of volcanic rocks in the MOVF range widely from basanite to evolved trachyte and comendite with a suite of intermediate rock types. Here we present 40Ar/39Ar ages, petrography, and whole-rock and mineral geochemistry to establish the temporal and magmatic evolution of the magmatic system. Volcanic activity occurred from 21.2 to 6.9 Ma, making it one of the longest records of volcanism in the western Ross Sea area. Mount Rittmann, an active volcano that is part of the MOVF, is not discussed here but extends the timing of volcanism of the MOVF into the Holocene. At Mount Overlord and surrounding areas, there were eruptions of lava flows, domes, and pyroclastic rocks. Localized deposits of hyaloclastites formed by magma-ice interactions provide an insight into former ice levels. Geochemically the MOVF shows a single magma differentiation trend except for Navigator Nunatak lavas which have a potassic affinity rarely seen in northern Victoria Land. Partial melting of an amphibole-bearing mantle lithology at or near the base of the continental lithospheric mantle (CLM) was the main source of the parental basaltic magmas. Polybaric crystal fractionation of the primary basaltic magmas mainly occurred at lower crustal depths and involved fractionation of clinopyroxene, olivine, kaersutite, feldspars, biotite, Fe–Ti oxides, apatite, and sodalite. Crustal assimilation of c. 10% granite harbor igneous complex granitoids was important in the evolution of intermediate composition magmas. Trachyte, phonolite, and comendite magmas stagnated and evolved at shallow crustal depths (c. <8 km). Over 95% crystal fractionation was required to generate the comendites. Extraction of the comendite melt from a felsic crystal mush was an important process. The potassic Navigator Nunatak magma required partial melting of phlogopite-bearing metasomatized CLM. The metasomes had ‘HIMU-like’ or FOZO isotopic compositions that ultimately originated from recycling of materials in the mantle. The MOVF displays a stronger affinity toward FOZO than other northern Victoria Land basaltic rocks. This suggests that the interaction between parental melt and juvenile CLM was limited, which is similar to volcanic rocks from the oceanic Adare Basin seamounts. Our result emphasizes the critical importance of a thick CLM for the genesis of diverse alkaline magma compositions in a continental rift system. 

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5. Mantle sources interpreted from mafic volcanoes adjacent to the andesitic Goat Rocks volcanic complex, southern Washington Cascades

   https://doi.org/10.1130/abs/2020AM-359181  

   Wall, K.T.; Grunder, A.L.; Weis, D (October 2020, Proceedings of the Geological Society of America for)

   An assessment of changing sources of basalt magmas feeding the Goat Rocks Volcanic Complex, SW Washington Cascades, over the 3 million year lifespan of the system. 

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