High-pressure serpentinization and abiotic methane formation in metaperidotite from the Appalachian subduction, northern Vermont

Serpentinization is the process of hydroxylation olivine-rich ultramafic rocks to produce minerals such as serpentine, brucite and magnetite. This commonly accompanied by Fe oxidation release H2, which can be involved in abiotic reaction pathways leading genesis light hydrocarbons methane (CH4). Examples this phenomenon exist at seafloor, serpentinite-hosted Lost City hydrothermal field, on land ophiolites relatively shallow depths. However, possibility for serpentinization occur greater depths, especially subduction zones, raises new questions convergent margin its impact deep carbon cycle. High-pressure bodies exhumed metamorphic belts provide insights mechanisms high-pressure zones chemistry resulting fluids. study focuses Belvidere Mountain complex belonging Appalachian belt northern Vermont, USA. Microstructures show overgrowth both primary (Mg# 0.91) 0.95) olivine delicate antigorite crystals, pointing least one stage high-temperature conditions consistent with evolution complex. Formation ubiquitous magnetite local Fe–Ni alloys testifies partial Fe2+ into Fe3+ generation reduced conditions. Fluid inclusion trails cross-cutting relicts suggest their formation during event. MicroRaman spectroscopy fluid inclusions reveals a CH4-rich gaseous composition, well N2, NH3 H2S. Moreover, precipitation daughter lizardite indicate initial presence H2O fluid. driven infiltration metasediment-derived aqueous fluids proposed origin CH4 other species preserved inclusions. suggests an example hydrocarbon related early Paleozoic zone.