Integrated Fluid Inclusion and P–T Dataset from the Himalayan Orogen: Recalculated Fluid Properties and Isochore Constraints with Implications for Fluid Evolution and the Global Carbon Cycle

This dataset represents a comprehensive compilation of mineral P–T conditions and fluid inclusion (FI) data from all lithotectonic units of the Himalayan orogen, significantly enhancing our understanding of this intricate geological system. It encompasses data from the Sub-, Lesser-, Higher-, and Tethyan Himalaya, as well as the Indus–Tsangpo Suture Zone and its associated magmatic arc. The compilation integrates previously published microthermometric results—eutectic temperature (Te), final ice-melting temperature (Tm,ice), CO2 homogenization temperature (ThCO2), and total homogenization temperature (Th)—to recalculate the salinity, density, and molar volume of trapped fluids using updated equations of state and modern fluid inclusion programs. Isochores have been constructed for each lithotectonic unit to infer the pressure–temperature (P–T) conditions of fluid entrapment, maximum burial depths, and metamorphic pathways.
The recalculated data offer a unified foundation for intercomparison across the orogen, facilitating a quantitative reconstruction of Himalayan fluid evolution through successive tectonometamorphic stages—from early diagenesis and subduction-related metamorphism to crustal thickening, partial melting, and exhumation. The results indicate that carbonic and aqueous–carbonic fluids are prevalent throughout the orogen, extending from the Lesser Himalayan metasediments to the ultrahigh-pressure eclogites of the Tso-Morari Complex. This continuous presence and movement of CO₂-bearing fluids during the orogenic cycle underscore the dynamic nature of the Himalayan orogen. Furthermore, the identification of N₂-rich inclusions in UHP rocks emphasizes the involvement of reduced nitrogen fluids in deep subduction and their potential role in redox buffering and crust–mantle volatile exchange.
Collectively, this dataset illustrates that CO₂- and N₂-bearing fluids were not only present but also served as key agents in metamorphic devolatilization, rock weakening, and carbon transfer throughout the Himalayan evolution. Their widespread occurrence suggests that the Himalaya operated as a dynamic trans-crustal fluid system capable of both releasing and sequestering carbon over geological timescales. These findings establish a crucial link between the fluid history of the Himalayan orogen and the global carbon cycle, emphasizing the role of collisional mountain belts as pivotal regulators of atmospheric CO₂ through deep Earth degassing and surface weathering feedbacks.