川西磨西断裂湾东地热水化学特征及成因机制  

Hydrochemical characteristics and genetic mechanism of geothermal water in the Wandong geothermal area along the Moxi fault in western Sichuan

作　　者：黄珣 张云辉[1,2] 李晓[2] 吕国森[1] 郭宏洋 HUANG Xun;ZHANG Yunhui;LI Xiao;LYU Guosen;GUO Hongyang(Faculty of Geosciences and Engineering,Southwest Jiaotong University,Chengdu 611756,China;State Key Laboratory of Geohazard Prevention and Geoenvironmental Protection,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]西南交通大学地球科学与工程学院,四川成都611756 [2]成都理工大学地质灾害防治与地质环境保护国家重点实验室,四川成都610059

出　　处：《煤田地质与勘探》2024年第6期91-101,共11页Coal Geology & Exploration

基　　金：国家自然科学基金项目(42102334,42072313);四川省科技计划项目(2022NSFSC0413,2023YFS0356);地质灾害防治与地质环境保护国家重点实验室开放基金项目(SKLGP2022K017)。

摘　　要：【目的】地热能开发是实现碳达峰、碳中和的重要途径。磨西断裂位于川西鲜水河断裂南段,拥有丰富的地热资源,是未来地热能开发的重点区域。【方法】对四川磨西断裂湾东地热区开展水文地球化学研究,通过水化学相关性分析其水-岩作用过程,利用地热温标、硅-焓混合模型等方法计算其热储温度、冷热水混合比例,采用氢氧同位素探明补给来源和补给高程。【结果和结论】结果显示:磨西断裂地热水的水化学类型包括HCO_(3)·Cl-Na型和HCO_(3)·SO_(4)-Ca·Mg型。地热水的水化学组分主要受水-岩作用(泥盆系大理岩方解石矿物溶解)影响,其中HCO_(3)·Cl-Na型地热水在磨西断裂深部受岩浆水混合和CO_(2)脱气作用影响。HCO_(3)·Cl-Na型地热水热储温度较高(159.16~228.57℃),沿磨西断裂循环深度较大;HCO_(3)·SO_(4)-Ca·Mg型地热水的热储温度较低(111.02~138.04℃),沿次级构造草科断裂运移,循环深度较小。地热水的补给来源均为大气降水和深部岩浆水,补给区为湾东地热区西部贡嘎山,补给高程在2 382~2 981 m。本次研究探明了湾东地热区存在2种不同成因模式,其水化学特征和热储温度差异显著,可为该区地热能开发提供更具针对性的理论依据。[Objective]Geothermal energy exploitation is identified as a vital way to achieve the goals of peak carbon dioxide emissions and carbon neutrality.The Moxi fault,located in the southern segment of the Xianshuihe fault zone in western Sichuan,boasts abundant geothermal resources,serving as a significant area for subsequent geothermal energy exploitation.[Methods]This study investigated the hydrogeochemistry of the Wandong geothermal area along the Moxi fault,analyzed the water-rock interaction process in the area based on the hydrochemical correlation,and calculated the reservoir temperatures and the mixing ratios of cold and hot water using geothermometers and the silica-enthalpy mixing model.Furthermore,this study investigated the recharge sources and elevations of geothermal water based on hydrogen and oxygen isotopes.[Results and Conclusions]Key findings are as follows:(1)Geothermal water along the Moxi fault exhibits hydrochemical types of HCO_(3)·Cl-Na and HCO_(3)·SO_(4)-Ca·Mg.The hydrochemical composition of geothermal water is subjected principally to water-rock interactions(i.e.,the dissolution of calcite in Devonian marbles).Besides,the HCO_(3)·Cl-Na geothermal water is further affected by the mixing of magmatic water and the CO_(2)degasification in the deep part of the Moxi fault.This type of geothermal water displays relatively high reservoir temperatures ranging from 159.16℃to 228.57℃and large circulation depths along the Moxi fault.In contrast,the HCO_(3)·SO_(4)-Ca·Mg geothermal water exhibits relatively low temperatures varying between 111.02℃and 138.04℃and small circulation depths along the Caoke fault,a secondary structure.(2)The geothermal water is recharged by meteoric water and deep magmatic water.Its recharge area resides in the Gongga Mountain in the western Wandong geothermal area,with recharge elevations ranging from 2382 m to 2981 m.Two genetic modes of geothermal water in the Wandong geothermal area were identified,manifesting significantly different hydrochemical characteri

关 键 词：地热水 水-岩作用 热储温度 补给来源 成因模式 四川磨西断裂 

分 类 号：P314[天文地球—固体地球物理学]