Collaborative Research: Geothermal Fluxes of Solutes, Heat, and Carbon Dioxide to the River System of Central Nepal

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0087671DerryIntegrated study of hot spring and stream chemistry in major tributaries of the Narayani river system of central Nepal, and stable isotope and fluid inclusion studies of associated hydrothermal vein material is underway. Data on the sources of solutes and sediments in Himalayan rivers indicate that active geothermal systems near the Main Central Thrust and in the Thakola graben are important sources of heat and solutes (including Na, K, Ca, Cl, Ge, Si and Sr), and release CO2 from metamorphic decarbonation reactions at depth 13C values from hot spring fluids are as high as +130/00, indicating a metamorphic source of CO2. About 25% of the flux of dissolved K and Sr, 12-15% of dissolved Si, and 90% of Cl at the confluence with the Trisuli river are derived from hydrothermal sources near the MCT. The heat loss from the surface springs is near 80 m W/m2 averaged over the area of the High Himalayan Crystalline series in the Marsyandi basin.This data indicate that geothermal activity along the MCT has a significant impact on geochemical and heat fluxes in the Himalaya.Data from hot springs and tributaries in the major tributary drainage of the Narayani (Kali Gandaki, Seti, Marsyandi, Bhuri, and Trisuli rivers) are being used to construct a chemical and water flux mass balance for the hydrothermal systems. Chemical mass balance of conservative tracers including SO4 /=Cl- and Ge/Se will be used to estimate hydrothernal contributions to river fluxes. Fluid inclusion and stable isotope analysis of undeformed "contribution to river Fluxes. Fluid inclusion and stable isotope analysis of undeformed "post-metamorphic" quartz and calcite veins will be used to estimate reservoir conditions, water-rock ratios, and local geothermal gradients in the convective system. The study is providing important data-driven estimate of geothermal heat flow and carbon degassing from the Himalaya that will help resolve difficulties with current Himalayan river budgets for radiogenic Sr and other dissolved species and new understanding to both our knowledge of Himalayan tectonic processes and how they impact geochemical fluxes.