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Evidence for microbial activity in British and Irish Ordovician pillow lavas
Author(s) -
Parnell John,
Hole Malcolm,
Boyce Adrian J.
Publication year - 2014
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.2562
Subject(s) - pillow lava , pyrite , seafloor spreading , geology , ordovician , basalt , geochemistry , seawater , paleontology , oceanography , volcanic rock , volcano
Pyrite is consistently found in modern seafloor vesicular basalts and has a sulphur isotopic composition consistent with microbial activity. We present S isotope data from pyrite in Ordovician pillow lavas at localities across the British Isles, which yield a range of δ 34 S compositions consistent with two components of sulphur: groundmass pyrite (~0 ± 4‰) and 32 S‐enriched pyrite in the vesicles (−8‰ to −27‰). The latter are recorded from vesicular lavas in four different terranes, representing different settings at the margins of the Iapetus Ocean. Whereas a component of magmatic sulphate is recognized in the groundmass values, the isotopically light data in the vesicles are consistent with microbial reduction of seawater sulphate in sub‐seafloor lavas. This is consistent with modern examples and indicates considerable longevity for this sub‐seafloor microbial habitat. Copyright © 2014 John Wiley & Sons, Ltd.