Massive production of abiotic methane during subduction evidenced in metamorphosed ophicarbonates from the Italian Alps.

ABSTRACT: Alteration of ultramafic rocks plays a major role in the production of hydrocarbons and organic compounds via abiotic processes on Earth and beyond and contributes to the redistribution of C between solid and fluid reservoirs over geological cycles. Abiotic methanogenesis in ultramafic rocks is well documented at shallow conditions, whereas natural evidence at greater depths is scarce. Here we provide evidence for intense high-pressure abiotic methanogenesis by reduction of subducted ophicarbonates. Protracted (≥0.5-1 Ma), probably episodic infiltration of reduced fluids in the ophicarbonates and methanogenesis occurred from at least ∼40 km depth to ∼15-20 km depth. Textural, petrological and isotopic data indicate that methane reached saturation triggering the precipitation of graphitic C

SUBMITTER: Vitale Brovarone A 

PROVIDER: S-EPMC5322563 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature