| 新疆塔什库尔干县曲曼地热田地下热水同位素研究 |
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| 引用本文：史杰,汪美华,马小军,文章,朱栗佟.2022.新疆塔什库尔干县曲曼地热田地下热水同位素研究[J].地球学报,43(5):645-653. |
| DOI：10.3975/cagsb.2022.040702 |
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| 基金项目:新疆维吾尔自治区地质勘查基金项目(编号: 2010006; N10-4-XJ01);中央返还两权价款项目(编号: N15-4-LQ1) |
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| 中文摘要:新疆塔什库尔干县曲曼地热田位于帕米尔高原中东部的塔什库尔干谷地北段, 钻孔揭露最高温度162 ℃。文章测定了曲曼地热田地下热水和地表水样品中的氢、氧、硫、氦等同位素, 结合B、Br、Cl等地热地球化学特征, 对地热田的补给来源、补给区高程和气温、热源、循环特征等进行了分析。测试结果显示: 地下热水中δ18O为–8.00‰ ~ –10.77‰, δD为–72.50‰ ~ –82.12‰, δ34SCDT为21.10‰~23.76‰; 其他水体中δ18O为–10.50‰ ~ –13.03‰, δD为–81.68‰ ~ –93.87‰, δ34SCDT为1.16‰~7.05‰; 4He值为0.01×10–4, 3He/4He为0.397 Ra; 地下热水中B含量为2.6~13.1 mg/L。对数据进行分析后得到以下结论: (1)曲曼地热田δD-δ18O分布在大气降水线下方且具有向右上方延伸的特点, TDS值为1~4 g/L, rNa/rCl(毫克当量比值)>0.85, Cl/Br(体积分数比值)>300, 是以大气降水为主要补给来源的循环型地下热水, 补给区为地热田西南侧的高山区, 其高程约4657 m, 雨季气温–3~2 ℃; (2)曲曼地热田孔口出水温度较高、热储温度较大的ZK7、ZK22表现出较大的“氧-18漂移”量, δ18O漂移值分别为2.12‰和2.35‰, 推测其属于岩浆热源型地热系统; (3)地下热水比冷水富集D超过4‰, 34S同位素显示地下热水体具有深源硫的特点, 3He/4He具有大气和地壳混源的氦同位素组成特征, 地下热水中B的质量浓度是其他水体的27倍多, 说明地下热水循环深度较大, 同时在深循环过程中可能有少量初生岩浆水混入。 |
| 中文关键词:曲曼高温地热田 同位素 水化学 地热来源 补给条件 |
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| Isotope and Hydrogeochemical Characteristics of the Quman High Temperature Geothermal Field in Taxkorgan, Xinjiang |
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| Abstract:The Quman geothermal field in the Xinjiang region is located in the northern section of the Taxkorgan Tajik Autonomous County in the east-central part of the Pamir Mountains. The borehole exhibits a maximum temperature of up to 162 °C in the Quman geothermal field. In this study, we determined the O, H, S, and He isotopes in geothermal and surface water samples from the field. Combined with hydrologic geochemistry features such as B, Br and Cl, the recharge source, elevation and temperature of the recharge area, heat source of geothermal field, and circulation characteristics were analyzed. The results showed that in the geothermal water, the values of δ18O, δD, and δ34SCDT were –8.00‰ – –10.77‰, –72.50‰ – –82.12‰, and 21.10‰ – 23.76‰, respectively. In the surface water samples, the values of δ18O, δD, and δ34SCDT were –10.50‰ – –13.03‰, –81.68‰ – –93.87‰, and 1.16‰ – 7.05‰, respectively. The value of B was 2.6 – 13.1 mg/L. The value of 4He was 0.01×10–4, and the ratio of 3He to 4He was 0.397 Ra. After analyzing the data, the following conclusions were derived: (1) The δD-δ18O distribution in the Quman geothermal field is below the precipitation line and extends to the upper right. The value of total dissolved solids (TDS) was 1 – 4 g/L, the value of rNa/rCl was higher than 0.85, and the ratio of Cl to Br was higher than 300. The Quman geothermal field has circulating geothermal water, which is mainly supplied by meteoric water. The recharge area is a high mountain area on the southwest side of the geothermal field, with an elevation of 4657 m, and the temperature during the rainy season ranged from –3 to 2 °C. (2) The ZK7 and ZK22 with higher outlet water temperature and higher thermal storage temperature in the Quman geothermal field show larger ‘Oxygen-18 drift’, the δ18O drift value of the two boreholes was 2.12‰ and 2.35‰, respectively, which should be that of the magmatic heat source geothermal system. (3) The concentration of D in the geothermal water was 4‰ higher than that of the cold water. 34S isotope showed that the geothermal water has the characteristics of deep source sulfur. The ratio of 3He to 4He has the characteristics of the helium isotope composition of mixed atmospheric and crustal sources, the mass concentration of B in the geothermal water was 27 times more than that in other water bodies, which indicated that the geothermal water circulation is relatively deep, and a small amount of primary magmatic water mixing may happen during the deep circulation. |
| keywords:Quman high temperature geothermal field isotope hydrogeochemistry geothermal source recharge conditions |
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