Occurrence of Greigite in Gas Hydrate-bearing Frontal Thrust Sediments of the Hikurangi Margin, New Zealand at Site U1518, IODP Expedition 375
Abstract
Microbial activity, fluid and gas circulation, and gas hydrate are amongst very important factors which impact the original magnetic mineral assemblages in marine sediments. Secondary magnetizations related to the formation of ferrimagnetic iron sulfides have been reported in sediments from accretionary prisms (e.g. Nankai Trough, Cascadia Margin). In this study, we present rock magnetic results obtained in marine sediments from IODP Expedition 375 Site U1518 located at the northern Hikurangi Trough, offshore New Zealand. Site U1518 lies on the frontal accretionary wedge, west of the deformation front, and penetrates the Papaku Fault, a major thrust fault possibly hosting slow slip events. Our study is part of the characterization of deformation and physical properties in the hanging wall and footwall of the fault. We conduct a rock magnetic study in fine-grained sediments from the surface to 480 mbsf to characterize the magnetic mineral assemblages (abundance, grain size, composition). Preliminary results show downcore variations in coercivity which are related to the presence of greigite as evidenced by a gyroremanence acquisition and FORC measurements. The occurrence of greigite at Site U1518 is likely due to an elevated methane flux that leads to a shallow sulfate-methane transition and methane hydrate occurrences.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGP21A..08K
- Keywords:
-
- 0419 Biomineralization;
- BIOGEOSCIENCES;
- 1512 Environmental magnetism;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1522 Paleomagnetic secular variation;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1540 Rock and mineral magnetism;
- GEOMAGNETISM AND PALEOMAGNETISM