广东丰顺汤坑地热田热水中稀土元素特征及其影响因素  

REE characteristics and their influencing factors of the geothermal water in Tangkeng geothermal field,Fengshun,Guangdong Province

作　　者：李义曼[1,2,3] 陈凯 天娇[1,5] 程远志 罗霁[6] 庞忠和 LI Yiman;CHEN Kai;TIAN Jiao;CHENG Yuanzhi;LUO Ji;PANG Zhonghe(Key Laboratory of shale gas and geoengineering,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,100029;Innovation Academy for Earth Science,Chinese Academy of Sciences,Beijing,100029;University of Chinese Academy of Sciences,Beijing,100049;China University of Mining and Technology(Beijing),Beijing,100083;Institute of Earthquake Forecasting,China Earthquake Administration,Beijing,100036;State Power Investment Corporation Research Institute,Beijing,102209)

机构地区：[1]中国科学院地质与地球物理研究所页岩气与地质工程重点实验室,北京100029 [2]中国科学院地球科学研究院,北京100029 [3]中国科学院大学,北京100049 [4]中国矿业大学(北京),北京100083 [5]中国地震局地震预测研究所,北京100036 [6]国家电投集团科学技术研究院有限公司,北京102209

出　　处：《地质论评》2022年第3期993-1005,共13页Geological Review

基　　金：国家重点研发计划课题(编号:2019YFC0604901);自然科学基金重点资助项目(编号:42072328)的成果。

摘　　要：华南火成岩地区发育多期次的花岗岩及丰富的地热资源,二者关系密切。目前关于该区岩石的REE分异特征及其富集机理研究较多,但对地热水中REE的特征及其影响因素等研究较少。笔者以广东丰顺汤坑地热田为例,分析了地热水稀土元素的特征并且与浅层地下水和榕江河水进行对比,探讨其赋存特征以及影响因素。结果表明:该区地热水较榕江河水和浅层地下水稀土元素含量偏低,具有MREE富集的Eu正异常、Ce负异常的REE配分模式,这是碱性水溶解硅酸盐矿物的结果。水的REE含量与pH值呈正相关关系,且其赋存形式受pH值影响较大。碱性地热水中REE以络合物Ln(CO_(3))_(2)^(-)和LnCO_(3)^(+)形式为主,中性的榕江河水则以络合物LnCO_(3)^(+)为主,而偏酸性的浅层地下水REE以Ln^(3+)为主,含一定量的LnSO_(4)^(+)。Objectives:Geothermal resources and multi-phases granite are widely developed in igneous rock regions of South China and they have close relationships.Studies on differentiation properties and enrichment mechanism of rare earth elements(REE)of granite rock have been done a lot while that for geothermal water is seldom.Taking Tangkeng geothermal field in Guangdong province,this paper focuses on chemical properties and species of REE of geothermal water as well as their influencing factors.Methods:Geothermal water,shallow groundwater and RongJiang river water samples were collected and analyzed for pH,TDS,chemical components and REE.The REE data were normalized using PAAS standards before discussion.Inorganic species of REE were calculated using PHREEQC which is a widely used geochemical program.Results:The REE concentration of geothermal water is ranging from 20 ng/L to 204 ng/L and is lower than that of shallow groundwater(64~275 ng/L)and Rongjiang river water(131~264 ng/L).Unlike the relative smooth pattern of REE in granite,REE of geothermal water,shallow groundwater and Rongjiang river water show consistent right deviation pattern.All of them has obvious negative Ce anomaly and positive Eu anomaly.Conclusions:Geothermal water exhibits REE distribution pattern with positive Eu anomaly and negative Ce anomaly enriched by MREE.This is probably caused by silicate minerals dissolution under alkaline conditions.REE content show positive correlations with pH and also its species are affected by pH.REE of alkaline geothermal water are dominated by complex of Ln(CO_(3))_(2)^(-)and LnCO_(3)^(+)while that of neutral Rongjiang River water and slightly acid shallow groundwater are mainly composed of LnCO_(3)^(+)and Ln^(3+)with certain content of LnSO_(4)^(+),respectively.

关 键 词：广东丰顺汤坑地热田 稀土元素 Eu正异常 花岗岩 华南火成岩 

分 类 号：P314[天文地球—固体地球物理学]