Deep Carbon Input and Shallow Decoupling in Tibetan Geothermal Gases Revealed by a C_He Isotope Consistency Framework

Geothermal gases from hot springs can carry information about fluids and carbon released from deep within Earth. However, these gases may be strongly changed as they rise toward the surface, for example by dissolution in groundwater, addition of crustal helium, or loss of carbon dioxide. This study compiles 612 geothermal gas samples from 308 hot_spring sites across the Tibetan Plateau and develops a carbon-helium isotope framework to test whether measured gas compositions are still consistent with deep sources.