1. Geochemical evidence for the nonexistence of supercritical geothermal fluids at the Yangbajing geothermal field, southern Tibet.
- Author
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Wang, Yingchun, Li, Liang, Wen, Huaguo, and Hao, Yinlei
- Subjects
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SUPERCRITICAL fluids , *RADIOACTIVE decay , *GEOTHERMAL resources , *GEOTHERMAL wells , *URANIUM-lead dating , *CARBON dioxide , *ENERGY consumption , *GAS condensate reservoirs - Abstract
• The thermal decomposition of marine carbonates and metasediments is a source of CO 2. • The radioactive decay of U and Th within crustal granite is the dominant source of He. • Three thermal reservoirs were identified using multiple gas geothermometers. • The parent geothermal fluid had a temperature of ∼320 °C at an ∼8-km depth. • Yangbajing has no supercritical fluids, given its small, deep-seated magma chamber. Exploring and exploiting high-temperature (even supercritical) geothermal resources are significant to meet energy demands and reduce carbon emissions. The Yangbajing geothermal field is the most exploited in China, with the currently highest temperature (329.8 °C) measured in a geothermal well. However, whether there are supercritical geothermal fluids beneath the deep parts of this geothermal field is under controversy. In this paper, the water isotope, chemical compositions, and C–He isotopes of gas samples were collected and analyzed. The geothermal water originated from the mixing of meteoric water and magmatic water (25%). The sources of CO 2 in the geothermal field were dominated by the thermogenic degassing of carbonates and metasediments in the crust while the radioactive decay of U and Th in granite is the dominated source of He. The temperatures of three different reservoirs are 150 ± 15 °C, 250 ± 10 °C, and ∼320 °C (with a depth of ∼8 km), respectively. These were obtained using dissolved gas, soil CO 2 flux, and noble gas geothermometers. Unlike other supercritical geothermal fields worldwide with larger, shallower, basaltic magma chambers, the Yangbajing geothermal field has a deep-seated, small-scale, granitic magma chamber. Thus, its geological conditions are not conducive for gestating supercritical fluids. These results are of great significance for exploring and developing high-temperature (even ultra-high-temperature) geothermal resources in China. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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