Authigenic Greigite as an Indicator of Methane Diffusion in Gas Hydrate-Bearing Sediments of the Hikurangi Margin, New Zealand

Authigenic ferrimagnetic iron sulfides, essentially greigite (Fe 3 S 4 ), are commonly found in gas hydrate-bearing marine sediments of active accretionary prisms. Greigite is a by-product, either intracellular or extracellular, microbial activity, and therefore provides good indication processes which closely related to the occurrence hydrate. A high-resolution rock magnetic study was conducted at Site U1518 International Ocean Discovery Program Expedition 375, located frontal wedge Hikurangi Margin, offshore New Zealand. Samples were collected throughout entire recovered stratigraphic sequence, from surface ?492 m below seafloor (mbsf) includes P?paku fault zone. This aims document properties composition mineral assemblage U1518. Based on downhole coercivity variations, studied interval divided into five consecutive zones. Most samples have high remanent (above 50 mT) first-order reversal curves (FORC) diagrams typical single-domain greigite. The top hanging wall has intervals that display lower coercivity, similar coercivities measured zone footwall. widespread distribution linked methane diffusion hydrate mainly disseminated within sediments. In three footwall intervals, investigated higher resolution, an improved signal, especially stronger FORC signature, likely enhanced activity favors formation preservation Our findings Margin show close linkage between greigite, activity.