喜马拉雅东构造结地区地热成因分析

Analysis of Geothermal Origin in Eastern Himalayan Syntaxis

喜马拉雅东构造结地区是现今地球上构造活动最强烈、地貌演化最快的地区之一,属于地中海—喜马拉雅地热带,水热活动强烈。基于喜马拉雅东构造结的地热地质背景,采用野外调查、水化学和稳定同位素测试分析等手段,初步分析嘉黎地区深部地下热水发育特征及成因模式。结果表明,该区域地下热水均来自大气降水或冰雪融水,补给高程位于4500 m以上,推测补给区位于研究区西北部片麻岩山区;区内地下热水均为未成熟水,热水补给水源沿断裂循环至深部热储,随后受热对流上升至地表出露成温泉,热水上升至浅表部与冷水发生混合,冷热水最大混合比可达91%;采用二氧化硅温度计、阳离子温度计以及硅-焓模型估算出热储温度最高达380℃,热水在雅鲁藏布江结合带内循环深度达到6900 m。研究区深部热源主要来自雅鲁藏布江结合带及附近深大断裂,地表热显示主要受控于结合带两侧的次级张扭性断裂。本研究初步揭示了喜马拉雅东构造结嘉黎地区地热成因模式,可为该区重大工程建设和高温热害防治提供指导。

The eastern Himalayan syntaxis is one of the regions with the strongest tectonic activity and the fastest geomorphic evolution on the Earth.It belongs to the Mediterranean-Himalayan tropics with strong hydrothermal activities.Based on the geological background,the development characteristics and genetic model of the deep underground hot water at Jiali are preliminarily explored through field survey,hydrochemical and stable isotope analyses.The results show that the origin of local geothermal water comes from meteoric precipitation or ice/snow melting,and the recharge altitude is above 4,500 m.It is speculated that the recharge area is located in the mountainous gneissic region in the northwest of the study area.The geothermal water in the area is immature.The geothermal water replenishment source circulates along the faults to the deep thermal reservoir,and then ascends by heating and convection until it is exposed as hot springs.The geothermal water rises to the shallow surface and mixes with cold water at a mixing ratio reaching 91%.SiO2 thermometer,cation thermometer and silicon-enthalpy models are used to estimate the reservoir temperature,and the maximum reservoir temperature is 380℃.The depth of geothermal water circulation reaches 6,900 m in the Yarlung-Zangbo River junction zone.The local geothermal heat source comes mainly from the Yarlung-Zangbo River junction zone and the nearby deep faults,and the surface geothermal springs are mainly controlled by the secondary tensile and torsional faults on both sides of the junction zone.This study preliminarily revealed the geothermal genetic model at Jiali of the eastern Himalayan syntaxis,which can provide a scientific basis for the geothermal resource development and utilization,and for the planning and construction of major projects in the area.