Hydrothermal alteration and microbial sulfate reduction in peridotite and gabbro exposed by detachment faulting at the Mid-Atlantic Ridge, 15 degree 20'N (ODP Leg 209): A sulfur and oxygen isotope study

Whole rock sulfur and oxygen isotope compositions of altered peridotites and gabbros from near the 15 degree 20'N Fracture Zone on the Mid-Atlantic Ridge were analyzed to investigate hydrothermal alteration processes and test for a subsurface biosphere in oceanic basement. Three processes are i...

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Bibliographic Details
Published in:Geochemistry, geophysics, geosystems : G3 geophysics, geosystems : G3, 2007-08, Vol.8 (8), p.np-np
Main Authors: Alt, Jeffrey C, Shanks, Wayne C, Bach, Wolfgang, Paulick, Holger, Garrido, Carlos J, Beaudoin, Georges
Format: Article
Language:English
Subjects:
Alterations
Gabbro
Microorganisms
Reduction
Rock
Sulfates
Sulfides
Sulfur
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Summary:Whole rock sulfur and oxygen isotope compositions of altered peridotites and gabbros from near the 15 degree 20'N Fracture Zone on the Mid-Atlantic Ridge were analyzed to investigate hydrothermal alteration processes and test for a subsurface biosphere in oceanic basement. Three processes are identified. (1) High-temperature hydrothermal alteration (250-350 degree C) at Sites 1268 and 1271 is characterized by super(18)O depletion (2.6-4.4ppt), elevated sulfide-S, and high [delta] super(34)S (up to 2 wt% and 4.4-10.8ppt). Fluids were derived from high-temperature (>350 degree C) reaction of seawater with gabbro at depth. These cores contain gabbroic rocks, suggesting that associated heat may influence serpentinization. (2) Low-temperature (
ISSN:1525-2027
1525-2027
DOI:10.1029/2007GC001617