Structure and hydrothermal system of south Tibet, China

1994 Fiscal Year Final Research Report Summary

• Project/Area Number: 05044106
• Research Category: Grant-in-Aid for international Scientific Research
• Allocation Type: Single-year Grants
• Section: Joint Research
• Research Institution: KYUSHU UNIVERSITY
• Principal Investigator: EHARA Sachio Professor, Faculty of Engineering, Kyushu University, 工学部, 教授 (10002346)
• Co-Investigator(Kenkyū-buntansha): じん 宝福 西蔵地鉱局, 地球物理隊, 副隊長 ; 金 旭 長春地質学院, 応用地球物理系, 副教授 ; ITOI Ryuichi Associate Professor, Geothermal Research Center, Faculty of Engineering, Kyushu, 工学部, 助教授 (50108768) ; MOGI Tohru Research Associate, Faculty of Engineering, Kyushu University, 工学部, 助手 (80182161) ; JIN Xu Associate Proffessor, Deep Geophysical Research Section, Changchun University of ; JING Baofu Senior Engineer, Geophysics Exploration Team, Tibet Geology and Minerals Adminis
• Project Period (FY): 1993 – 1994
• Keywords: geothermal systems / geothermal reservoir / resistivity / geothermal alteration / Tibet, volcano / geothermal power / generation / geothermal energy development

Research Abstract

There are at least 60 high and intermediate temperature geothermal systems in the Himalayan Geothermal Belt. The Yangbajing geothermal field in south Tibet of China is one of typical, most active and most developed geothermal systems in the belt. However, the detailed geothermal structure was not clalified including the heat source (volcanic or non-volcanic) and the location of the upflow zone of deep geothermal fluids.
In this study, we conducted near-surface underground temperature measurements, geochemical surveys and magnetotelluric (AMT and ULFMT technique) surveys in and around the Yangbajing geothermal field. Near-surface temperature and geochemical data suggests a possibility of the deep upflow in the northern part of this field. The uprising deep geothermal fluids flow laterally to the southern part of the field.
The magnetotelluric data show shallow (shallower than 500m deep) and deep (several km depth) low resistivity zones in this field. The former is interpreted in terms of a shallow geothermal reservoir developed. in the Quaternary morainic layr and the latter in terms of hot intrusive rocks in the upper crust. This result shows that the origin of geothermal activities of this field may be volcanic, although recent volcanic rocks do not exsist at the surface.
Summarizing our data and previously obtained data. we constructed a conceputual hydrothermal model with deep vertical upflow in the northern part and shallow lateral flow of geothermal fluids in the southern part. Then we did numerical geothermal modelling based on the conceptual model. As a result, we obtained a good numerical hydrothermal model, which simulates well the observed temperature profiles and natural heat discharge data.