Collaborative Research: Experimental controls on Clumped Isotope Signatures of Methane in Deep-Sea Vents

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The project will study the controls on the chemical characteristics of methane gas in ocean hydrothermal systems. This project will use laboratory experiments to explore the isotopic composition of methane gas and carbon dioxide. Those lab data will enable future studies of CH4 and CO2 in seafloor vents. The study will inform studies of the cycling of carbon between the Earth’s interior and oceans. It is also relevant to life in extreme environments and the origin of life. Project broader impacts include research opportunities for graduate and undergraduate students and high-school summer interns. Graduate students from California State University, San Bernardino (a minority-serving institution) will spend time at the University of Maryland and the Carnegie Institution of Washington. There they will gain experience with state-of-the-art isotope geochemistry.Deep-sea hydrothermal vent systems affect the cycling of carbon between the Earth’s interior and oceans by introducing organic compounds of thermogenic, abiotic and microbial origin to the overlying water column. Vent fluids from both basalt and ultramafic-hosted hydrothermal systems contain abundant CH4 in addition to other organic species. This project aims to explore the origin and evolution of CH4 in deep-sea vents by employing the use of double-substituted and doubly-deuterated isotopologues (13CH3D, 12CH2D2). In a series of hydrothermal experiments involving organic matter decomposition. CO2 reduction and non-equilibrated CH4 gases in the presence of mineral catalysts, the distribution of rare methane isotopologue will be assessed by the use of a high-mass-resolution gas-source multiple collector mass spectrometer (Panorama, UMD). Experiments will assess the equilibrium relationships in the 12CH2D2-13CH3D-12CH3D-12CH4-13CH4-HD-HDO-H2O system and describe isotope effects associated with the impact of mineral phases and H2O H isotope composition on the abiotic and thermogenic formation mechanisms. This study aims to be a comprehensive study of Delta-12CH2D2 and Delta-13CH3D evolution applied to subseafloor hydrothermal systems and water/rock interactions deeper in the oceanic crust.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.