| 甘肃省地热流体化学及环境同位素特征和形成年龄分析 |
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| 引用本文： | 张凌鹏,丁宏伟,张家峰,王玉玺,田辽西.甘肃省地热流体化学及环境同位素特征和形成年龄分析[J].干旱区地理,2020,43(6):1496-1504. |
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| 作者姓名： | 张凌鹏 丁宏伟 张家峰 王玉玺 田辽西 |
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| 作者单位： | 1.甘肃省地矿局第二地质矿产勘查院，甘肃 兰州 730020； 2 甘肃省地质矿产 勘查开发局，甘肃 兰州 730000；3 甘肃省地矿局第一地质矿产勘查院，甘肃 天水
741020； 4 甘肃省地矿局第三地质矿产勘查院，甘肃 兰州 730050；
5 甘肃省地矿局水文地质工程地质勘察院，甘肃 张掖 734000 |
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| 基金项目： | 中国地质科学院《中国矿产地质志?甘肃卷?水气资源》项目（DD20160346，DD20190379）；中国地质调查局项目（1212011
3077300）；甘肃省地下水工程及地热资源重点实验室开放基金项目（20190512） |
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| 摘 要： | 利用大量的地热流体化学成分及环境同位素（δD、δ18O、14C）测试数据，深入分析了隆起山地 构造对流型、沉降盆地传导型地热流体的化学特征及分布规律，进而对地热流体的环境同位素分 布特征及形成年龄进行了梳理总结，得出了明确的结论。结果表明：隆起山地构造对流型地热田 地热流体主要以断裂上升泉的形式出露，分布于西秦岭-祁连造山带，补给来源为当地及周边大气 降水入渗，地热流体形成年龄一般小于 5 000 ~ 30 000 a，水质较好，属“开启型”的地热系统；热储层 岩性、断裂规模及水热循环方式和深度等明显控制着地热流体化学类型、环境同位素特征和形成 年龄。沉降盆地传导型地热田地热流体主要以管井开采的方式出露；热储埋藏深度小于 1 600 m 的 地热井，地热流体补给来源为当地及周边大气降水入渗，形成年龄一般小于 5 000 ~ 30 000 a，水质
相对较好，属“半开启-半封闭型”的地热系统；热储埋藏深度介于 1 600 ~ 2 600 m 之间的地热开采 井，主要为地质历史时期逐步形成的“古水”，水化学类型复杂且水质较差，地热流体形成年龄介于
30 000 ~ 50 000 a,属“封闭型”的地热系统；热储层岩性、埋藏深度、地下水在岩层中的滞留时间与循 环深度等明显控制着地热流体化学类型、环境同位素富集程度和形成年龄。
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| 关 键 词： | 热流体 水化学 环境同位素 形成年龄 地热系统 |
Hydrochemistry and environmental isotopic characteristics and formation ages analysis of geothermal fluids in Gansu Province |
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| ZHANG Ling-peng,DING Hong-wei,ZHANG Jia-feng,WANG Yu-xi,TIAN Liao-xi.Hydrochemistry and environmental isotopic characteristics and formation ages analysis of geothermal fluids in Gansu Province[J].Arid Land Geography,2020,43(6):1496-1504. |
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| Authors: | ZHANG Ling-peng DING Hong-wei ZHANG Jia-feng WANG Yu-xi TIAN Liao-xi |
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| Abstract: | Based on a large number of chemical composition and environmental isotope (δD, δ18O, 14C) test data of geothermal fluid, this paper analyzes the chemical characteristics and distribution rules of the convective and conductive geothermal fluid in the uplifted mountainous area, Gansu Province, China. The environmental isotope distribution characteristics and formation ages of the geothermal fluid are then then analyzed. Results show that the geothermal fluid in the convective geothermal field in the uplifted mountainous area is mainly exposed in the form of fracture rising spring, which is distributed in the west Qinling and Qilian orogenic belt. The source of supply is the infiltration of local and surrounding atmospheric precipitation. The formation age of the geothermal fluid is generally less than 5 000- 30 000 a and good water quality is observed. Hence, the geothermal fluid belongs to the“open” geothermal system. The geothermal fluid in the conductive geothermal field in the subsidence basin is mainly exposed by tube well exploitation. Exploitation wells with a buried depth of less than 1 600 m are supplied by the infiltration of local and surrounding atmospheric precipitation. Here, the formation ages of the geothermal fluid are generally less than 30 000 a and the water quality is relatively good. Hence, this belongs to the“semi-open semi- closed”geothermal system. The geothermal open exhibits a buried depth of 1 600-2 600 m. The production wells are mainly the“ancient water”formed gradually in the geological historical period with a complex hydrochemical type and with poor water quality. This then belongs to the“closed”geothermal system with the formation ages of geothermal fluid between 30 000-50 000 a. Generally speaking, the lithology of the thermal reservoir, burial depth, retention time, and circulation alternation of groundwater in the rock layer obviously control the chemical type, environmental isotope, and formation ages of geothermal fluid. Based on the geothermal occurrence law, if the buried depth of the thermal reservoir is deeper, the geological conditions are more closed, and δD and δ18O are more enriched, indicating that the formation age of the fluid is older. |
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| Keywords: | thermal fluid hydrochemistry environmental isotope formation age geothermal system |
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