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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.
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Data report: thermal diffusivity, thermal conductivity, and volumetric heat capacity at borehole observatory Sites U1518 and U1519, Hikurangi Subduction Zone, IODP Expedition 375
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.
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- Award ID(s):
- 2412279
- PAR ID:
- 10646894
- Publisher / Repository:
- International Ocean Discovery Program
- Date Published:
- Journal Name:
- Proceedings of the International Ocean Discovery Program Expedition reports
- Volume:
- 372375
- Issue:
- 213
- ISSN:
- 2377-3189
- ISBN:
- 978-1-954252-65-3
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Book Chapter:
- https://doi.org/10.14379/iodp.proc.372B375.213.2025
