藏南隆子县模麓温泉群水文地球化学特征及成因机制研究_周鹏.pdf

周鹏，孙明露，张云辉，等，2023.藏南隆子县模麓温泉群水文地球化学特征及成因机制研究J.沉积与特提斯地质，43(2)：322339.doi:10.19826/ki.1009-3850.2023.04003ZHOU P，SUN M L，ZHANG Y H，et al.，2023.Hydrogeochemical Characteristics and Genetic Mechanism of theMolu Geothermal Springs in the Longzi County,Southern TibetJ.Sedimentary Geology and Tethyan Geology，43(2)：322339.doi:10.19826/ki.1009-3850.2023.04003藏南隆子县模麓温泉群水文地球化学特征及成因机制研究周鹏1，孙明露2*，张云辉3，荣峰1，达娃1，万忠焱1，刘恭喜1，彭清华4，胡华山4，旦增4，刘振峰4（1.西藏自治区地勘局地热地质大队，西藏拉萨850000；2.西藏大学，西藏拉萨850000；3.西南交通大学，四川成都611756；4.中国地质调查局军民融合地质调查中心，四川成都611732）摘要：藏南地区地热资源丰富，是喜马拉雅地热带的重要组成部分，有望成为新的地热资源开发靶区。本文以藏南桑日-错那活动构造带内模麓温泉群为研究对象，以水化学和氢氧氚同位素为研究方法，分析模麓温泉群的水岩作用、热储温度、补给来源及径流时间，揭示了地热水的成因机制。模麓地热水 pH 在 6.67.2 之间，TDS 为 1 908mg/L2 326 mg/L，水化学类型以 HCO3Cl-Na 型和 HCO3Cl-NaCa 型为主。地热水中主要阴阳离子来源于硅酸盐矿物的溶解和少量地球深部物质。利用硅-焓方程法和硅-焓图解法计算的初始热储温度为 198256，冷水混入比例为 68%85%。此外，对地热水中的 Li、B、F 等微量元素分析得出，研究区温泉水中微量组分除来自水-岩作用外，应该还与深部流体的混入有关，且该地区的氢氧同位素特征表明地下水补给主要来源于大气降水，补给高程为 5 652m5 664m，模麓地热水中的氚含量0.5TU，表明其地热水为老水，有更长的径流时间，为水-岩作用提供了充足的时间，而宿麦郎曲河水为新水，补给径流时间短。研究区地热水与围岩遮拉组砂板岩发生水-岩作用，进行离子交换作用，在地下水运移过程中加热形成地热水，最终在有利构造部位出露形成温泉群。本次研究初步揭示了藏南模麓温泉的成因机制，可为藏南地热资源开发利用提供理论参考。关键词：模麓温泉；水文地球化学；热储温度；补给来源；成因机制中图分类号：P314 文献标识码：AHydrogeochemical Characteristics and Genetic Mechanism of the MoluGeothermal Springs in the Longzi County,Southern TibetZHOU Peng1，SUN Minglu2*，ZHANG Yunhui3，RONG Feng1，DA Wa1，WAN Zhongyan1，LIU Gongxi1，PENG Qinghua4，HU Huashan4，DAN Zeng4，LIU Zhenfeng4（1.Geothermal and Geological Party,Tibet Bureau of Mineral Resource Exploration and Development,Lhasa 850000,China；2.Tibet University,Lhasa 850000,China；3.Southwest Jiaotong University,Chengdu 611756,China；4.Civil-Military IntegratedGeological Survey Center of China Geological Survey,Chengdu 611732,China）Abstract：The geothermal resources in southern Tibet are abundant,being an important part of the Himalayan Geothermal Belt,isexpected to become a new prospective area for geothermal resource development.In this paper,we analyzed the water-rock 收稿日期：2022-01-09；改回日期：2023-03-07；责任编辑：曹华文；科学编辑：唐渊作者简介：周鹏（1987），男，工程师，从事地热地质调查研究。E-mail：通讯作者：孙明露（1996），女，硕士，主要从事地热成因研究。E-mail：资助项目：国家自然科学基金（42072313，42102334）、中国地质调查局项目（ZD20220418）、西藏自治区找矿专项资金项目（GZFCG2022-7078）第 43 卷 第 2 期 Vol.43 No.22023 年 6 月沉 积 与 特 提 斯 地 质 Sedimentary Geology and Tethyan GeologyJun.2023interaction,geothermal reservoir temperature,recharge source and runoff time of the geothermal springs in the active tectonic zone ofthe Sangri-Cuona in southern Tibet,and then revealed the genesis mechanism of geothermal water by hydrochemistry and hydrogen-oxygen-tritium isotopes.The pH values of the Molu geothermal water ranged from 6.6 to 7.2,and the TDS values were 1 908 mg/L to 2 326mg/L.The hydrochemical types were mainly HCO3Cl-Na and HCO3Cl-NaCa types.The main anions and cations in geothermalwater were originated from the weathering of silicate minerals and minor deep materials.The initial geothermal reservoirtemperatures calculated using the silica-enthalpy equation method and silica-enthalpy diagramming method were 198256,andthe cold water mixing percentages were 68%85%.In addition,the analysis of Li,B,F and other trace elements in geothermal watershowed that the trace components in geothermal water in the study area were not only from water-rock interaction,but also related tothe mixing of deep thermal fluids in geothermal water.The hydrogen and oxygen isotope characteristics of the area show that thegroundwater recharge was mainly from atmospheric precipitation,the recharge elevation is 5 652 m5 664 m,and the tritium contentin the geothermal water in the foot of the model was less than 0.5TU,indicated that the geothermal water was old water.It showedthat there was a longer runoff time,which provided sufficient time for water-rock interaction,while the Sumai Langqu River waterwas fresh water and the runoff time was short.The geothermal water in the study area had water-rock interaction in the diabase rocksof the Zhela Formation,and ion exchange was carried out.In the process of groundwater migration,geothermal water formed byheating and then exposed as geothermal springs in beneficial structural positions.This study preliminarily reveals the geneticmechanism of geothermal waters in southern Tibet,which can provide theoretical reference for the development and utilization ofgeothermal resources in southern Tibet.Key words：Molu geothermal spring；Hydrogeochemistry；Geothermal reservoir temperature；Recharge source；Geneticmechanism 0引言随着人口的增长、工业化的加速和生活水平的提高，能源短缺一直是全世界面临的严峻问题（Guo et al.,2017;Chang et al.,2021）。因此，近几十年来世界各地掀起了可再生能源开发利用的热潮（Wang et al.,2021;Erba and Bozda,2022）。地热能与水能、太阳能、风能等其它可再生能源对比，具有清洁、环保、用途多样的特点，且不易受季节、昼夜及气候变化等因素的影响，开发利用更为稳定，并且能源利用效率更高，将为实现“碳达峰、碳中和”目 标 做 出 重 要 贡 献（Zhang and Hu,2018;Moraga et al.,2022;Muther et al.,2022）。地热能开发利用的关键前提是探明地热资源的成因机制。目前水文地球化学、地球物理勘查和数值模拟等方法均被用来分析地热资源的成因机制（郭镜和夏时斌,2022;Gudala et al.,2022;Prez-Zrate et al.,2022;Zhou et al.,2022）。其中，水文地球化学分析在地热资源的成因机制研究中扮演着重要角色。水化学组分可以判定地热水的水化学类型和水岩作用过程，地球化学地热温标（阳离子、二氧化硅和硅-焓模型等）是估算地热储层温度的有效手段，氘氧（D-O）同位素分析能够追溯地热水的补给来源