Venting the roof of the world: Active faults circulate meteoric fluids through upper-crustal geothermal systems of the Himalaya-Tibet orogen

Abstract Geothermal activity is widespread across the Himalaya-Tibet orogen, yet links between upper-crustal fluid circulation and deeper heat and fluid sources remain poorly understood. We integrate geochemical and isotopic data from 214 thermal springs with fault maps to characterize heat sources and permeability pathways. Stable isotopes (δ18O–δD) show meteoric recharge is the primary fluid source, with little to no direct interaction with magma bodies. Fault-controlled springs—slightly over half the data set—are statistically hotter and dominate among the hottest springs. Southern Tibet hosts the highest density of hot springs, typically along north-south rifts or conjugate northwest- and northeast-striking strike-slip faults, yielding crustal 3He/4He ratios. Springs in northern Tibet are on average cooler but have mantle-derived 3He/4He ratios, with the hottest springs associated with active strike-slip faults. The hotter temperatures, yet crustal 3He/4He signature, in southern-Tibet springs relate to upper-crustal heat flow elevated by partial melting and Neogene exhumation, despite a colder deep lithosphere. Geothermal systems are controlled by extensional and transtensional fault geometries that enhance upper-crustal permeability within the convergent orogen, enabling meteoric circulation in a region of average to high continental heat flux.