This presentation reveals that Himalayan hot springs are key to understanding the region's carbon cycle, with geochemical analysis showing that fault-controlled meteoric water circulation drives metamorphic CO2 degassing. Water penetrates to depths of ~5 km, creating pathways for deep-sourced CO2 to reach the surface, particularly along seismically active faults. The hot springs release significant amounts of CO2 (up to 1.5 × 10¹¹ mol/yr, with total degassing flux reaching 3.0 × 10¹¹ mol CO₂ yr⁻¹), which is comparable to the region's silicate weathering sink. The degassed CO2 is primarily derived from metamorphic decarbonation (~78%) reactions, and can turn the orogen into a net source of CO2 on million-year time scales.
Indra Sen is an Associate Professor at the Indian Institute of Technology-Kanpur, India. His research interest is in the application of isotope geochemistry in tracing surface and deep Earth processes.