Carbon dioxide degassing flux from two geothermal fields in Tibet, China

Abstract

Over geological time scales, Earth degassing has a significant impact on atmospheric carbon dioxide (CO2) concentrations, which are an important component of global carbon cycle models. In Tibet, structural conditions and associated widespread geothermal systems lead to carbon dioxide degassing during geothermal water migration. We characterized the hydrochemical conditions of two geothermal fields on the Tibetan Plateau. The chemical composition of geothermal waters was controlled by K-feldspar and albite. Geothermal waters in the Langjiu geothermal field were sodium chloride type and those of the Dagejia geothermal field were sodium bicarbonate type. Simulations of CO2 partial pressure within the two hydrogeothermal systems showed that CO2 degassing occurs during hot water migration from the aquifer to the surface. Carbon dioxide degassing flux from the Langjiu geothermal field was estimated to be ~3. 6×106 kg km-2 a-1, and that from Dagejia was ~3.3×106 kg km-2 a-1. © 2011 The Author(s).