Spatiotemporal characteristics of hydrothermal volatiles from the Tengchong volcanic field in the southeastern Tibetan Plateau: A probable constraint on the genesis of intraplate volcanism

Determining parent magmatic sources of active and dormant volcanoes is crucial for understanding their formation and geodynamic processes. The Tengchong volcanic field (TCV), an intraplate volcanic group located in the southeastern part of the Qinghai–Tibet Plateau, is linked to mantle disturbances through the eastward subduction of the Indian plate. By comprehensive analysis helium and carbon isotopes in hot springs in the TCV, this study revealed that volatile degassing within the TCV predominantly originated from the mantle. Volatile degassing history, coupled with a helium magma aging model, corroborated that the helium of the parent magma was similar to that found in oceanic island basalts , probable sourced from stagnant oceanic slab dehydration above the mantle transition zone, firstly providing compelling geochemical evidence for the upwelling of profound mantle materials. This research not only elucidates the enigmatic geothermal behaviors of intraplate volcanoes but also enhances our understanding of the tectonic dynamics of SE Tibetan Plateau. • Helium–carbon volatiles in modern groundwater detected mantle upwelling derived by subducting of Indian oceanic slab. • The degassing history of mantle helium combined with estimated initial helium indicates the location of primordial magma. • Subducted oceanic slab down to MTZ and dehydration provided parent magmatic materials for the Tengchong volcanic field.