Title: Data report: permeability, porosity, pore size, grain size, and microporosity of sediments from IODP Expedition 372/375 Sites U1517, U1518, and U1519
Constant rate-of-strain consolidation, nuclear magnetic resonance transverse relaxation time distribution, mercury injection capillary pressure, grain size distribution, and nitrogen adsorption microporosity measurements were performed on 13 whole-round core samples from International Ocean Discovery Program (IODP) Expedition 372/375 along the Hikurangi margin offshore New Zealand. In this report, whole-round core samples were analyzed from three different sites along the Hikurangi margin subduction zone: Sites U1517 and U1519 on the upper slope and Site U1518 near the Hikurangi Trench. All samples were composed of mostly silty clay to clayey silt sediments. Measurements were used to constrain in situ permeability, porosity, pore size distribution, and consolidation characteristics. Across seven samples from Site U1517, in situ permeability of clayey silts ranged 3.0 × 10−17 to 1.5 × 10−15 m2 and median pore sizes ranged 180–246 nm. A transition from overconsolidated to underconsolidated sediments as expressed by the overconsolidation ratio was identified between 50 and 73 meters below seafloor that aligned with the observed base of the Tuaheni Landslide Complex. Across samples at Site U1518, in situ permeability of silty clays ranged 3.7 × 10−16 to 5.5 × 10−15 m2 and median pore sizes ranged 140–320 nm. Across samples at Site U1519, permeability of silty clays ranged 6.4 × 10−16 to 6.0 × 10−14 m2 and median pore sizes ranged 187–300 nm. more »« less
Screaton, E.J.; Summerfield, C.; Jaeger, J.M.; Whipple, J.
(, Proceedings of the International Ocean Discovery Program)
null
(Ed.)
A total of 15 whole-round core samples from International Ocean Discovery Program Expeditions 372 and 375 were tested for vertical permeability. The samples were recovered from four sites. Sites U1517 and U1519 are located on the upper slope, Site U1518 is located near the trench, and Site U1520 is located seaward of the trench. Measured vertical permeability varied from 5.7 × 10−19 m2 to 1.7 × 10−16 m2. Unless cores were too consolidated to disaggregate, subsamples were taken and analyzed for grain size. The tested samples contained 35.4%–66.3% clay-sized (<4 µm), 32.7%–51.7% silt-sized (4–63 µm), and 0.5%–23.1% sand-sized (>63 µm) fractions.
Fulton, PM; Kitajima, H
(, Proceedings of the International Ocean Discovery Program Expedition reports)
We report laboratory measurements of thermal conductivity and thermal diffusivity and calculated values of volumetric heat capacity for 56 core samples collected during International Ocean Discovery Program Expedition 375 from Sites U1518 and U1519 in the Hikurangi subduction zone. These sites are instrumented with borehole observatories that include downhole temperature sensors, enabling eventual integration of laboratory-derived thermal properties with in situ thermal data. Measurements were conducted under saturated conditions using a transient plane source technique and include repeated tests for quality control. Volumetric heat capacity was calculated as the ratio of thermal conductivity to thermal diffusivity, using measurements obtained simultaneously on the same sample. At Site U1518, thermal diffusivity averages 5.055 ± 0.610 × 10−7 m2/s (± one standard deviation) and volumetric heat capacity averages 2.588 ± 0.277 MJ/(m3·K). At Site U1519, thermal diffusivity averages 5.395 ± 1.027 × 10−7 m2/s and volumetric heat capacity averages 2.574 ± 0.350 MJ/(m3·K). Measured thermal conductivity values average 1.294 ± 0.123 W/(m·K) at Site U1518 and 1.354 ± 0.131 W/(m·K) at Site U1519 and are consistent with previous shipboard results. These new constraints on thermal properties provide key input for interpreting borehole temperature records and modeling transient heat transport in subduction zone fault systems.
Alamoudi, O; Tisato, N; Van_Avendonk, H J; Garza, H; Bangs, N L
(, AGU)
The northern part of the Hikurangi margin (HM) regularly experiences shallow slow-slip events (SSEs), possibly extending into the thrust faults of the sedimentary prism. For example, offshore Gisborne SSEs occur every 1-2 years and can last several weeks, during which 5-30 cm of slip may be accommodated. Understanding what controls the timing of such events will help the comprehension of HM deformation and earthquake mechanics in general. One hypothesis for a slow slip mechanism is that the low permeability of the HM prism rocks and the large fluid volumes dragged deep into the subduction zone cause over-pressures along the megathrust and prism splay faults. Overpressure induces SSEs that locally increase permeability. After an SSE, swelling clays and ductile deformation reduce permeability within months, resetting the conditions for developing overpressure. We tested such a hypothesis by measuring the hydraulic permeability of fractured sedimentary rocks making up the core of the accretionary prism. Tests were performed using a newly developed X-ray transparent pressure vessel mounted inside a micro-computed tomography scanner (mCT) that allowed in-situ observation of fracture evolution as a function of confining pressure, time, and exposure to water. The tested rocks were probably subducted to ~7.5 km and are calcareous-glauconitic fine-grained sandstones with a silty matrix from the Late Cretaceous-to-Paleocene Tinui Group containing ~15% vol% of clay minerals. After exposure to high confining pressure and water, the samples regained pre-fracture permeability in tens of days. mCT imagery suggests that fracture clogging, possibly due to clay expansion, controls healing. We propose that slow slip events in the northern HM open fault fractures and allow drainage at the beginning of the slip cycle, followed by fracture clogging due to swelling clays and ductile deformation, with the duration of the cycle regulated by the interplay of these processes.
Underwood, M.B.
(, Proceedings of the International Ocean Discovery Program)
Sediments deposited on the upper slope of the Hikurangi subduction margin, offshore New Zealand, are composed mostly of hemipelagic mud with interbeds of silt to sand that were modified after deposition by strong bottom currents. Some of those deposits were spot cored at Site U1519 during International Ocean Discovery Program (IODP) Expedition 375. This report provides the results of 76 X-ray diffraction analyses of the clay-sized fraction (<2 µm spherical settling equivalent). Sampling focused on the background lithology of hemipelagic mud. Normalized weight percent values for common clay-sized minerals (where smectite + illite + undifferentiated [chlorite + kaolinite] + quartz = 100%) reveal unusually small amounts of scatter both within and between the two lithostratigraphic units. The mean and standard deviation (σ) values for Unit I are smectite = 44.1 wt% (σ = 3.7), illite = 34.0 wt% (σ = 2.8), undifferentiated (chlorite + kaolinite) = 10.7 wt% (σ = 1.3), and quartz = 11.2 wt% (σ = 2.2). The mean and standard deviation values for Unit II are smectite = 49.9 wt% (σ = 5.5), illite = 31.9 wt% (σ = 4.0), undifferentiated (chlorite + kaolinite) = 5.8 wt% (σ = 1.8), and quartz = 12.3 wt% (σ = 7.4). Large gaps between cored intervals preclude recognition of possible depth-dependent or age-dependent trends, but the values at Site U1519 closely match those at nearby Site U1517 (Tuaheni Landslide Complex). Two major unconformities were interpreted in seismic reflection profiles that cross Site U1519, and compositional differences across those features are trivial. Variations among indicators of clay diagenesis are also relatively small. The average value of the illite crystallinity index is 0.537Δ°2θ (σ = 0.019). The expandability of smectite + illite/smectite mixed-layer clay averages 79% (σ = 3%), and the average proportion of illite in illite/smectite mixed-layer clay is 13% (σ = 6%).
International Ocean Discovery Program (IODP) Expedition 372 combined two research topics, slow slip events (SSEs) on subduction faults (IODP Proposal 781A-Full) and actively deforming gas hydrate–bearing landslides (IODP Proposal 841-APL). Our study area on the Hikurangi margin, east of the coast of New Zealand, provided unique locations for addressing both research topics. SSEs at subduction zones are an enigmatic form of creeping fault behavior. They typically occur on subduction zones at depths beyond the capabilities of ocean floor drilling. However, at the northern Hikurangi subduction margin they are among the best-documented and shallowest on Earth. Here, SSEs may extend close to the trench, where clastic and pelagic sediments about 1.0–1.5 km thick overlie the subducting, seamount-studded Hikurangi Plateau. Geodetic data show that these SSEs recur about every 2 years and are associated with measurable seafloor displacement. The northern Hikurangi subduction margin thus provides an excellent setting to use IODP capabilities to discern the mechanisms behind slow slip fault behavior. Expedition 372 acquired logging-while-drilling (LWD) data at three subduction-focused sites to depths of 600, 650, and 750 meters below seafloor (mbsf), respectively. These include two sites (U1518 and U1519) above the plate interface fault that experiences SSEs and one site (U1520) in the subducting “inputs” sequence in the Hikurangi Trough, 15 km east of the plate boundary. Overall, we acquired excellent logging data and reached our target depths at two of these sites. Drilling and logging at Site U1520 did not reach the planned depth due to operational time constraints. These logging data will be augmented by coring and borehole observatories planned for IODP Expedition 375. Gas hydrates have long been suspected of being involved in seafloor failure; not much evidence, however, has been found to date for gas hydrate–related submarine landslides. Solid, ice-like gas hydrate in sediment pores is generally thought to increase seafloor strength, as confirmed by a number of laboratory measurements. Dissociation of gas hydrate to water and overpressured gas, on the other hand, may weaken and destabilize sediments, potentially causing submarine landslides. The Tuaheni Landslide Complex (TLC) on the Hikurangi margin shows evidence for active, creeping deformation. Intriguingly, the landward edge of creeping coincides with the pinch-out of the base of gas hydrate stability on the seafloor. We therefore hypothesized that gas hydrate may be linked to creep-like deformation and presented several hypotheses that may link gas hydrates to slow deformation. Alternatively, creeping may not be related to gas hydrates but instead be caused by repeated pressure pulses or linked to earthquake-related liquefaction. Expedition 372 comprised a coring and LWD program to test our landslide hypotheses. Due to weather-related downtime, the gas hydrate-related program was reduced, and we focused on a set of experiments at Site U1517 in the creeping part of the TLC. We conducted a successful LWD and coring program to 205 mbsf, the latter with almost complete recovery, through the TLC and gas hydrate stability zone, followed by temperature and pressure tool deployments.
Nole, M, and Daigle, H. Data report: permeability, porosity, pore size, grain size, and microporosity of sediments from IODP Expedition 372/375 Sites U1517, U1518, and U1519. Retrieved from https://par.nsf.gov/biblio/10572652. Proceedings of the International Ocean Discovery Program Expedition reports 372B/375.211 Web. doi:10.14379/iodp.proc.372B375.211.2024.
Nole, M, & Daigle, H. Data report: permeability, porosity, pore size, grain size, and microporosity of sediments from IODP Expedition 372/375 Sites U1517, U1518, and U1519. Proceedings of the International Ocean Discovery Program Expedition reports, 372B/375 (211). Retrieved from https://par.nsf.gov/biblio/10572652. https://doi.org/10.14379/iodp.proc.372B375.211.2024
Nole, M, and Daigle, H.
"Data report: permeability, porosity, pore size, grain size, and microporosity of sediments from IODP Expedition 372/375 Sites U1517, U1518, and U1519". Proceedings of the International Ocean Discovery Program Expedition reports 372B/375 (211). Country unknown/Code not available: International Ocean Discovery Program. https://doi.org/10.14379/iodp.proc.372B375.211.2024.https://par.nsf.gov/biblio/10572652.
@article{osti_10572652,
place = {Country unknown/Code not available},
title = {Data report: permeability, porosity, pore size, grain size, and microporosity of sediments from IODP Expedition 372/375 Sites U1517, U1518, and U1519},
url = {https://par.nsf.gov/biblio/10572652},
DOI = {10.14379/iodp.proc.372B375.211.2024},
abstractNote = {Constant rate-of-strain consolidation, nuclear magnetic resonance transverse relaxation time distribution, mercury injection capillary pressure, grain size distribution, and nitrogen adsorption microporosity measurements were performed on 13 whole-round core samples from International Ocean Discovery Program (IODP) Expedition 372/375 along the Hikurangi margin offshore New Zealand. In this report, whole-round core samples were analyzed from three different sites along the Hikurangi margin subduction zone: Sites U1517 and U1519 on the upper slope and Site U1518 near the Hikurangi Trench. All samples were composed of mostly silty clay to clayey silt sediments. Measurements were used to constrain in situ permeability, porosity, pore size distribution, and consolidation characteristics. Across seven samples from Site U1517, in situ permeability of clayey silts ranged 3.0 × 10−17 to 1.5 × 10−15 m2 and median pore sizes ranged 180–246 nm. A transition from overconsolidated to underconsolidated sediments as expressed by the overconsolidation ratio was identified between 50 and 73 meters below seafloor that aligned with the observed base of the Tuaheni Landslide Complex. Across samples at Site U1518, in situ permeability of silty clays ranged 3.7 × 10−16 to 5.5 × 10−15 m2 and median pore sizes ranged 140–320 nm. Across samples at Site U1519, permeability of silty clays ranged 6.4 × 10−16 to 6.0 × 10−14 m2 and median pore sizes ranged 187–300 nm.},
journal = {Proceedings of the International Ocean Discovery Program Expedition reports},
volume = {372B/375},
number = {211},
publisher = {International Ocean Discovery Program},
author = {Nole, M and Daigle, H},
}
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