Open AccessThinned crust in southwest Pacific may harbor gas hydrate
Author(s) -
Auzende JeanMarie,
Dickens Gerald R.,
Van de Beuque Sabrina,
Exon Neville F.,
François Caroline,
Lafoy Yves,
Voutay Olivier
Publication year - 2000
Publication title -
eos, transactions american geophysical union
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.316
H-Index - 86
eISSN - 2324-9250
pISSN - 0096-3941
DOI - 10.1029/00eo00127
Subject(s) - clathrate hydrate , geology , lithology , crust , sediment , hydrothermal circulation , hydrate , seawater , continental crust , seabed , mineralogy , oceanography , geophysics , geomorphology , petrology , paleontology , chemistry , organic chemistry
The Lord Howe Rise (LHR) is a large, complex, and poorly studied fragment of thinned continental crust submerged 750–3000 m beneath the oligotrophic waters of the central Tasman Sea (Figure 1). Deep seismic profiles taken during recent cruises in the region have revealed an intriguing phenomenon: the eastern slope of the LHR has a prominent and extensive bottom simulating reflector (BSR) that cross‐cuts lithology at 0.65–0.75 s two‐way travel time (twt) [ Exon et al ., 1998; Lafoy et al ., 1998]. Given best estimates for sonic velocity (1600 m/s) and thermal gradients (0.9+0.04°C/m) in sediment on the LHR, predicted temperatures and pressures at the depth of the BSR lie on the CH 4 ‐CH 4 hydrate‐seawater equilibrium curve. Thus, the BSR on the LHR most likely represents an interface between gas hydrate and free gas [e.g., Dickens et al ., 1997]. Although BSRs and gas hydrates are increasingly found in the marine realm, the LHR discovery has raised an interesting conceptual problem c oncerning the origin of gas hydrates.