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Physical Properties and Gas Hydrate at a Near‐Seafloor Thrust Fault, Hikurangi Margin, New Zealand
Author(s) -
Cook Ann E.,
Pagai Matteo,
Clennell Michael Benedict,
McNamara David D.,
Nole Michael,
Wang Xiujuan,
Han Shuoshuo,
Bell Rebecca E.,
Solomon Evan A.,
Saffer Demian M.,
Barnes Philip M.,
Pecher Ingo A.,
Wallace Laura M.,
LeVay Leah J.,
Petronotis Katerina E.
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl088474
Subject(s) - geology , seafloor spreading , fault (geology) , clathrate hydrate , petrology , seismology , accretionary wedge , thrust fault , fault gouge , drilling , subduction , geophysics , tectonics , hydrate , mechanical engineering , chemistry , organic chemistry , engineering
The Pāpaku Fault Zone, drilled at International Ocean Discovery Program (IODP) Site U1518, is an active splay fault in the frontal accretionary wedge of the Hikurangi Margin. In logging‐while‐drilling data, the 33‐m‐thick fault zone exhibits mixed modes of deformation associated with a trend of downward decreasing density, P ‐wave velocity, and resistivity. Methane hydrate is observed from ~30 to 585 m below seafloor (mbsf), including within and surrounding the fault zone. Hydrate accumulations are vertically discontinuous and occur throughout the entire logged section at low to moderate saturation in silty and sandy centimeter‐thick layers. We argue that the hydrate distribution implies that the methane is not sourced from fluid flow along the fault but instead by local diffusion. This, combined with geophysical observations and geochemical measurements from Site U1518, suggests that the fault is not a focused migration pathway for deeply sourced fluids and that the near‐seafloor Pāpaku Fault Zone has little to no active fluid flow.