Abstract
The thermal-waters resources in Weihe Basin of Shaanxi province, NW China are historically classified as middle- to low- temperature thermal-waters in China. Recent exploitation of the deep thermal reservoir in the centre part of the basin (i.e. Xi’an and Xianyang) had observed plentiful supply of thermal fluid with higher measured maximum temperature (120°C) and higher hydraulic pressure (80.50 MPa) in the deeper (more than 4,000 m deep) sedimentary basin. A recent isotope study shows that deep geothermal waters in the cities of Xi’an and Xianyang are characterized by an observable horizontal oxygen-18 (δ18O) shift and minor deuterium (2H) enrichment. The considerable oxygen shift is possibly due to the following four reasons: water–rock interaction at high temperature, slow circulation rate of water, low water-to-rock ratio, and old age. On the end number of the δ18O shift, minor δ2H enrichment occur when there is higher concentrations of H2S, CH4, I and Br with lower rate of rSO4 2−/rCl− and r +Na /r −Cl suggesting relatively isolated geological environment. In a few thermal waters points, \(r{\text{Na}}^{{\text{+}}} {\text{/}}r{\text{Cl}}^{-}\) < 0.85. This shows possible presence of formation waters. Combining the results from isotopic study and chemical analysis, we can classify the types of geothermal waters into three groups, the shallow and fast circulating system, the semi-circulating system and the deep and slow circulating system.
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The work described has been carried out with the financial support of the China Geological Survey Bureau and the National Science Foundation of China.
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Ma, Z., Yu, J., Su, Y. et al. δ18O shifts of geothermal waters in the central of Weihe Basin, NW China. Environ Earth Sci 59, 995–1008 (2010). https://doi.org/10.1007/s12665-009-0092-7
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DOI: https://doi.org/10.1007/s12665-009-0092-7