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Ultrahigh-precision noble gas isotope analyses reveal pervasive subsurface fractionation in hydrothermal systems

2023; American Association for the Advancement of Science; Volume: 9; Issue: 15 Linguagem: Inglês

10.1126/sciadv.adg2566

2375-2548

David V. Bekaert, Peter H. Barry, Michael W. Broadley, David Byrne, Bernard Marty, C. J. Ramírez, J. Maarten de Moor, Alejandro Rodríguez, Michael R. Hudak, Adam V. Subhas, Sæmundur A. Halldórsson, Gerdhard L Jessen, Jenny M. Blamey, Andri Stefánsson, Antonio Caracausi, Karen G. Lloyd, Donato Giovannelli, Alan Seltzer,

Methane Hydrates and Related Phenomena

Mantle-derived noble gases in volcanic gases are powerful tracers of terrestrial volatile evolution, as they contain mixtures of both primordial (from Earth’s accretion) and secondary (e.g., radiogenic) isotope signals that characterize the composition of deep Earth. However, volcanic gases emitted through subaerial hydrothermal systems also contain contributions from shallow reservoirs (groundwater, crust, atmosphere). Deconvolving deep and shallow source signals is critical for robust interpretations of mantle-derived signals. Here, we use a novel dynamic mass spectrometry technique to measure argon, krypton, and xenon isotopes in volcanic gas with ultrahigh precision. Data from Iceland, Germany, United States (Yellowstone, Salton Sea), Costa Rica, and Chile show that subsurface isotope fractionation within hydrothermal systems is a globally pervasive and previously unrecognized process causing substantial nonradiogenic Ar-Kr-Xe isotope variations. Quantitatively accounting for this process is vital for accurately interpreting mantle-derived volatile (e.g., noble gas and nitrogen) signals, with profound implications for our understanding of terrestrial volatile evolution.