地学前缘 ›› 2014, Vol. 21 ›› Issue (6): 356-371.DOI: 10.13745/j.esf.2014.06.034

• 论文 • 上一篇    下一篇

西藏尼木—那曲地热流体成因及幔源流体贡献

刘昭，蔺文静，张萌，谢鄂军，刘志明，王贵玲   

  1. 1. 中国地质科学院 水文地质环境地质研究所, 河北 石家庄 050061 2. 中国地质大学(武汉) 环境学院, 湖北 武汉 430074 3. 西藏自治区地质矿产勘查开发局 地热地质大队, 西藏 拉萨 850032
  • 收稿日期:2013-12-04 修回日期:2014-03-26 出版日期:2014-11-15 发布日期:2014-11-15
  • 作者简介:刘昭(1983—)，男，博士研究生，主要从事地热及地下水资源研究。E-mail:liuzhao0129@126.com
  • 基金资助:

    中国地质调查局地质调查项目(1212011220840)；国家高技术研究发展计划“863”项目“干热岩地热地质资源评价与开发技术研究”(2012AA052802)

Geothermal fluid genesis and mantle fluids contributions in NimuNaqu, Tibet

  • Received:2013-12-04 Revised:2014-03-26 Online:2014-11-15 Published:2014-11-15

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摘要：

研究区位于尼木—那曲高温地热带，处在当雄—羊八井—多庆错活动构造带的中北段，本次选取11个未开发的地热田，收集并采集区内地热流体数据，与羊八井深、浅部热储进行对比研究，对完善区内高温地热系统成因机理，为后期勘探及钻探提供重要的参考意义。从水化学数据分析，高温地下热水主要为Cl-Na、Cl·HCO3-Na水，中低温地下热水主要为HCO3-Na水，地下热水中Li、F、SiO2、HBO2与Cl大体上存在正相关关系，显示可能有岩浆水的混入；从氢氧同位素数据分析，地下热水主要为大气降水补给，在董翁、宁中高温地热田发生轻微的氧18漂移，谷露地热田氧18漂移较其他地热田明显，宁中、谷露及罗玛地下热水中氚含量小于1 TU，主要是次现代水的补给，月腊处氚含量为8.4 TU，推断主要为现代水的补给，其他地热田地下热水推测是次现代和最近补给之间的混合；地热气体以CO2和N2为主，二者呈现良好的负相关，从CO2气体碳同位素、He同位素比值及综合指标分析，气体来源主要为壳源，在宁中及玉寨地热田，R/Ra值大于1，存在明显的幔源物质释放现象，幔源He所占比例为2.73%～30.93%。概括区内典型高温地热田的成因模式，为后期地热田深入研究及开发利用提供重要的科学依据。

 

关键词: 西藏, 地热流体, 气体, 幔源流体, 成因

Abstract:

Study area is located in the Nimu—Naqu hightemperature geothermal belt, within the MiddleNorth section of the DangxiongYangbajain—Duoqingcuo active tectonic belt. Eleven unexploited geothermal fields are selected for this study, the hydrochemistry, hydrogen and oxygen isotope data, geothermal gases and their isotope data are collected and gathered from the study area, and the comparison with shallow and deep reservoirs in Yangbajain are conducted, in order to improve the study of genetical mechanism of the hightemperature geothermal systems and provide guidance for exploration and drilling in the area. Based on the analytical data of hydrochemistry of geothermal fluids, the chemical types of the high temperature thermal water are mainly of Cl-Na or Cl·HCO3-Na type, and the lowtemperature thermal water is mainly of HCO3-Na type. There is likely a positive correlation between Li, F, SiO2, HBO2 and Cl, which indicates the possible mixing of magmatic water. From stable isotope data, the thermal water showed mainly meteoric recharge. The thermal water show slight “18O drift” in Dongweng, Ningzhong hightemperature geothermal fields. The phenomenon is more obvious in Gulu geothermal field than the others. The tritium contents are less than 1 TU in Ningzhong, Gulu and Luoma, indicating mainly submodern water recharge, the trtium content at Yuela is 8.4 TU, which can be inferred to modern water recharge. The underground thermal water from other geothermal fields is the hybrid water recharge of submodern with recent water. The geothermal gases are mainly composed of carbon dioxide and nitrogen; there is a good negative correlation between the contents of carbon dioxide and nitrogen. Judging from the carbon isotopes and helium isotopes from carbon dioxide, combining with comprehensive index analysis, the source of the geothermal gases is mainly derived from the crust. However, the monitored R/Ra values are greater than 1 in Ningzhong and Yuzhai,showing that there must be a significant release of mantle material. The proportion of mantle helium ranges from 2.73 to 30.93 percent. Finally, the comprehensive study of the genesis model for typical, high-temperature geothermal field in the study area, will provide an important scientific basis for the further research as well as the development and utilization of the geothermal fields.

 

Key words: Key words: Tibet, geothermal fluids, gases, mantle fluids, genesis

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