Evidence for microbial activity in British and Irish Ordovician pillow lavas

John Parnell*, Malcolm Hole, Adrian J. Boyce

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


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 δ34S compositions consistent with two components of sulphur: groundmass pyrite (~0±4‰) and 32S-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.

Original languageEnglish
Pages (from-to)497-508
Number of pages12
JournalGeological Journal
Issue number4
Early online date15 May 2014
Publication statusPublished - 1 Jul 2015


  • Basalt
  • Deep biosphere
  • Ireland
  • Ordovician
  • Pillow lava
  • Scotland
  • Wales


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