Structure and hydrothermal system of south Tibet, China

中国藏南构造与热液系统

基本信息

批准号：
05044106
负责人：
EHARA Sachio
金额：
$ 2.56万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

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.

喜马拉雅地热带至少有60个高温和中温地热系统。我国藏南羊八井地热田是该带典型、最活跃、最发育的地热系统之一。然而，详细的地热结构尚未明确，包括热源（火山或非火山）以及深层地热流体上流带的位置。在本研究中，我们进行了近地表地下温度测量、地球化学调查和大地电磁（ AMT和ULFMT技术）羊八井地热田及其周边地区的调查。近地表温度和地球化学数据表明该油田北部可能存在深层上升流。上升的深层地热流体横向流向该气田南部。大地电磁数据显示该气田存在浅层（浅于500m）和深层（几公里深）低电阻率区。前者是根据已开发的浅层地热储层来解释的。就第四纪冰碛层而言，后者就上地壳的热侵入岩而言。这一结果表明，尽管地表不存在近期的火山岩，但该区域的地热活动起源可能是火山。总结我们的数据和之前获得的数据。建立了北部深层垂直上升流、南部浅层地热流体横向流动的热液概念模型。然后我们根据概念模型进行了地热数值模拟。结果，我们获得了一个良好的数值热液模型，该模型很好地模拟了观测到的温度剖面和自然放热数据。