A Comparative Study of Geothermal Fields Along the Qinghai-Tibet Railway

Abstract

Qinghai-Tibet Plateau is rich in high temperature geothermal resources, among which the graben along the Qinhai-Tibet Railway is a favorable zone in terms of development. However, which is the field with highest energy potential has been an unsettled issue. In August 2012, we collected water samples from four geothermal fields including: Gulu, Jidaguo, Ningzhong, and Yuzhai and measured water chemistry and isotopes to get insights into their water recharge and reservoir temperatures. The results found in the literature for Yangbajing geothermal field has been used for a comparison. The geothermal waters are originated from local meteoric precipitation, but exhibit obvious oxygen shift due to strong water-rock interaction at elevated temperatures. The oxygen shift at Gulu hot spring waters are the most intensive, higher than 2.7ñ, while it is lower than 2ñ for the other geothermal waters. The elevation of recharge area for the geothermal waters has been estimated from 5700 m in Jidaguo to less than 5000 m for other systems. The geothermal reservoir temperatures have been estimated using cation and silica thermometers. The highest temperature is 240Ž at Gulu geothermal field, slightly lower than that of Yangbajing but higher than other fields. In conclusion, Gulu is the best geothermal field among those to be developed.