Pore Water Geochemistry of IODP Exp 315 and 316: The NanTroSEIZE Transect
Abstract
IODP Exp 315 and 316 drilled six sites as part of the first stage of NanTroSEIZE, an international, multi-year endeavor to elucidate earthquake-related processes. These six sites form a transect southeast of the Kumano Basin, Japan with boreholes that penetrated the Kumano forarc basin (C0002), the megasplay fault region (C0001, C0004, and C0008) and the frontal thrust including sediment from the subducting plate (C0006 and C0007). One element of this drilling is to evaluate the relationship between pore fluid behavior and slip and deformation in the crust. To help address this relationship 322 pore water samples were extracted from sediment whole rounds. Each of the whole rounds was scanned (CT) before it was processed within a nitrogen-filled glove bag and squeezed to express the pore fluid. In addition, 15 samples from C0002 underwent the GRIND technique to gather baseline pore water chemical data for future deep drilling where highly indurated sediments likely exist. Each of these pore water samples underwent a range of analytical procedures at sea. Additional procedures were conducted ashore. Combined, these procedures resulted in data for 30 chemical species including the stable isotopic composition of O and H in water. These data provide the most thorough preliminary reports tables in the history of DSDP, ODP and IODP, and ongoing measurements include a range of isotopic (e.g., I, B, Sr, Li, C), ionic (e.g., REE), and organic measurements. We will present all of the data that appear in the preliminary reports including GRIND samples for comparison to squeezed samples. Our presentation will highlight changes in pore water composition along the transect of boreholes, putting individual site-related pore water chemical profiles in a broader context. Pore water profiles in the upper about 30 m of the sediment column are dominated by microbially mediated reactions with a highly defined sulfate-methane transition. Deeper within the sediment the dissociation of gas hydrates and diagenetic reactions dominate the composition of pore waters. On the basis of these pore water chemical analyzes, no clear evidence for present or past fluid flow exists, even along major faults that were bisected during drilling.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.T31B1990W
- Keywords:
-
- 1031 Subduction zone processes (3060;
- 3613;
- 8170;
- 8413);
- 1050 Marine geochemistry (4835;
- 4845;
- 4850);
- 3004 Gas and hydrate systems;
- 3021 Marine hydrogeology;
- 3060 Subduction zone processes (1031;
- 3613;
- 8170;
- 8413)