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引用本文:许鹏,谭红兵,张燕飞,张文杰. 特提斯喜马拉雅带地热水化学特征与物源机制[J]. 中国地质, 2018, 45(6): 1142-1154.
XU Peng,TAN Hongbing,ZHANG Yanfei,ZHANG Wenjie. Geochemical characteristics and source mechanism of geothermal water in Tethys Himalaya belt[J]. Geology in China, 2018, 45(6): 1142-1154(in Chinese with English abstract).
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特提斯喜马拉雅带地热水化学特征与物源机制
许鹏, 谭红兵, 张燕飞, 张文杰
河海大学, 地球科学与工程学院, 江苏 南京 210000
摘要:
西藏地热资源丰富,特别是其南部特提斯喜马拉雅地热带是一条现今仍然十分活跃的地热带。通过对该地热带10处代表性温泉野外调查及采样分析,讨论了水化学特征及水体中异常富集元素的物源机制。根据热储温度、水化学类型及水体中溶解的典型稀有分散性元素浓度,这些温泉可划分为两大类:一类包括卡乌、曲参岗、查巴曲珍和古堆温泉群,这些温泉热储温度均高于120℃,水化学类型以Na-Cl-HCO3型为主,特征性稀有分散性元素如Li、B和As等显著富集;另一类包括锡钦、哲古和曲果温泉,热储层温度相对较低,变化于60~110℃,水化学类型以CaNa-HCO3和Na-HCO3型为主,Li、B和As等元素浓度较低。第一类温泉系统,水化学成分除与水循环深度大、热储温度高导致更强的水岩作用过程密切相关外,水体中异常富集的Li、B和As等特殊化学成分更可能与演化晚期的残余岩浆流体来源有关。相比之下,第二类温泉系统主要代表了水循环深度较浅、地下水更替频繁、冷水混入比例较大的温泉,水化学成分主要受控于水-岩作用的强弱。因此,特提斯喜马拉雅带地热水体异常富集的稀有分散性元素物源机制主要受控于深部富含这些元素的流体混入过程。
关键词:  特提斯喜马拉雅地热带  水化学特征  热储温度  物源机制
DOI:10.12029/gc20180605
分类号:P641.3;P314.1
基金项目:国家自然科学基金(91747203,41173049,41872074)、中央高校基本科研业务费重点发展领域科研专项资金(2017B19614)联合资助。
Geochemical characteristics and source mechanism of geothermal water in Tethys Himalaya belt
XU Peng, TAN Hongbing, ZHANG Yanfei, ZHANG Wenjie
School of Earth Science and Engineering, Hohai University, Nanjing 211100, Jiangsu, China
Abstract:
Geothermal resources are very abundant in Tibet. A very active geothermal zone called the Tethys Himalaya geothermal belt has been developed in the southern part of the Tibetan Plateau. This belt is one of the most intense geothermal zones in modern as well as in ancient period in China's mainland, accounting for over 80 percent of the geothermal resources in Tibet. Through field investigations and sampling analyses for 10 typical hot springs from the geothermal area, the hydrochemical characteristics and source mechanisms are discussed. According to the thermal reservoir temperature, the hydrochemical type and the concentration of typical rare and dispersed elements dissolved in the water, the hot springs can be classified into two types:one type includes Kawu, Qucangang, Chabaquzhen and Gudui hot springs, their thermal reservoir temperatures are higher than 120℃ and they belong to NaCl-HCO3 type; some rare and dispersed elements such as Li, B and As are obviously enriched. The other type includes Xinqin, Zhegu and Quguo hot springs, their geothermal reservoir temperatures are relatively low (60-110℃); these springs show lower concentrations of elements of Li, B and As with water chemistry dominated by Ca-Na-HCO3 and Na-HCO3 type. The high concentration of water chemical composition in the first group is closely related to the deeper water circulation and the higher thermal reservoir temperature, and abnormal enrichment of Li, B and As in the hot springs are more likely to be related to the source of residual magmatic fluids. In contrast, the second group of hot springs mainly denotes a shallower water circulation depth and frequent cold groundwater replenishment and mixing. The formation and evolution of chemical compositions of water are mainly related to water/rock interactions.
Key words:  Tethys Himalayas geothermal belt  hydrochemical characteristics  temperature of thermal reservoir  source mechanisms