Preservation of biosignatures in metaglassy volcanic rocks from the Jormua ophiolite complex, Finland

摘要: Evidence of microbially-mediated alteration basaltic glass is preserved in originally glassy basalts (rims pillow lavas, hyaloclastite breccias, and chilled margins dykes) from the well-preserved 1.95Ga Jormua ophiolite complex (JOC) Northeastern Finland. Although textural evidence microbial commonly observed relic recent oceanic crust some ophiolites, these textures have been destroyed during greenschist to lower amphibolite facies regional metamorphism deformation JOC. However, another robust biosignature found generally depleted d 13 C values disseminated carbonate extracted basalts, relative crystalline samples. The same distribution well documented samples as ophiolites Phanerozoic age. This characteristic contrastinthe Cvaluesofdisseminatedcarbonateisinterpretedtoresultfrommicrobe-inducedfractionationduringoxidation organic matter. X-ray mapping initial zones has identified residual carbon associated with highly-concentrated S that unrelated carbonate. We attribute biosignatures material prior emplacement. © 2004 Elsevier B.V. All rights reserved.