Shuai Wang1, Xuelian Huang1, Xiaocheng Zhou2,3
(1 State Key Laboratory of Deep Geothermal Resources, School of Sustainable Energy, China University of Geosciences, Wuhan 430078, China; 2 Institute of Earthquake Forecasting, China Earthquake Administration, Beijing 100036, China; 3 School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China)
Abstract: Helium isotopes are sensitive tracers of deep fluid sources and pathways, yet their significance for testing models of plateau growth remains underexplored. The southeastern margin of the Tibetan Plateau (SETP) is commonly interpreted as a key region influenced by mid-lower crustal flow, but this model has been constrained mainly by geophysical and geodetic observations. Here we integrate newly collected geothermal gas data with published He-C isotope records to examine the spatial pattern of mantle-derived helium and its tectonic implications. A total of 78 gas samples from 44 hot springs along the Xianshuihe and Anninghe-Xiaojiang fault systems were analyzed for gas compositions, helium-neon isotopes, and carbon isotopes. After correcting for atmospheric components, samples from the Sichuan Basin and the middle Anninghe-Xiaojiang fault system show typical crustal helium signatures (RC/RA < 0.1), whereas mantle-derived helium is widely detected across much of the SETP (RC/RA > 0.1). High mantle helium signals occur in three focal regions: the Xianshuihe fault bending section, Tengchong volcanic field, and Simao volcanic field. In volcanic regions, the signals are related to shallow crustal magma degassing. In contrast, mantle helium anomalies above the cold Yangtze Craton and along the northern Anninghe-Xiaojiang fault system indicate that lateral crustal flow can transport and preserve mantle noble gas signals from the Tibetan Plateau toward the craton. The strongest signal in the Xianshuihe bending section further suggests that crustal movement, rapid uplift, denudation, and stress focusing may accelerate vertical ascent of mantle fluids. These results provide independent geochemical evidence for crustal-flow-driven growth of the SETP and highlight the need to consider active crustal deformation when interpreting noble gas signals in tectonically complex regions.
Keywords: Helium isotopes; Mantle-derived fluids; Crustal flow; Geothermal gases; Southeastern Tibetan Plateau; Tectonic degassing
Author Profile (first author): Shuai Wang, Male, Associate Professor, PhD, mainly engaged in geothermal geochemistry, noble gas isotope tracing, and deep fluid migration research. E-mail: wangshuai@cug.edu.cn
