First Estimates of Hydrothermal Helium Fluxes in Continental Collision Settings: Insights From the Southeast Tibetan Plateau Margin

Continental regions are essential for the outgassing of deeply-sourced helium in response to volcanic and tectonic processes. However, the helium fluxes remain largely unknown for continental collision settings such as the Tibetan Plateau. Here, we focus on hydrothermal helium degassing from the Simao block, Southeast Tibetan Plateau margin, and report flux estimates of (0.03 - 32) x 10(5) atoms m(-2) s(-1) for He-3 and (3.2 - 32) x 10(10) atoms m(-2) s(-1) for He-4, with mantle fractions of helium fluxes up to 2-3 orders of magnitude greater than those of stable continents. Geologically recent magma recharge beneath Quaternary volcanoes is proposed to account for the high mantle helium fluxes and He-3/He-4 up to 7.24 Ra. Active tectonics driven by the India-Asia continental collision possibly maintained efficient release of crustal helium over geological timescales. These findings present the first flux estimates for hydrothermal helium degassing controlled by volcanic and tectonic processes in continental collision settings.