【作者】 刘昭；

【导师】 王贵玲；

【作者基本信息】 中国地质科学院 ， 地质工程， 2014， 博士

【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。区内分布的高温地热显示类型多种多样,蕴藏着丰富的地热资源。但区内仅对羊八井和羊易地热田进行过系统的调查及研究工作,本文选取研究区11个未开发的地热田,收集并采集区内地热流体数据,与喜马拉雅地热带其他典型高温地热系统进行对比研究,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。本文从热源、地热流体流体运移通道、地热流体来源及热储特征4个方面对区内典型高温系统进行了研究,得到了如下认识：研究区高温地热系统的热源主要是壳内局部熔融层的贡献,活动断裂及深部构造对区内热水活动有明显的控制作用,青藏高原腹地地表断裂、地震活动、地热分布存在密切关系,与深部地质过程具有动力学成因联系。从水化学数据分析,高温地下热水主要为Cl-Na、Cl·HCO3-Na水,中高温地下热水主要为HCO3-Na水,地下热水中Li、F、SiO2、HBO2与C1大体上存在正相关关系,显示可能有岩浆水的混入；用地下热水地球化学温标及气体温标,估算重点地热田热储温度为90～270℃；利用氯焓及硅焓图解估算地下热水中有25%-75%比例不等的冷水混入。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1TU,主要是次现代水的补给,月腊处氚含量为8.4TU,主要为现代水的补给,其他地热田地下热水是次现代和最近补给之间的混合；地下热水中碳硫同位素特征的研究,揭示区内地下热水碳源和硫源主要来源于沉积层的淋滤作用,随着冷水混入大气成因来源不断增加,多数介于二者的过渡类型,部分有深部物质的来源。地热气体以CO：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%。上述研究显示高温地热系统热源和热水组分主要为壳内局部熔融体的贡献,地热流体向上运移过程中不断有大气降水成分混入；气体He同位素数据显示,在宁中及玉寨地热田存在幔源物质侵位。最后,结合区内地质资料、深部探测、重点地热田物探成果及地热流体地球化学分析成果,概括区内典型高温地热田的成因模式,提出了玉寨高温地热系统的概念模型,为后期地热田深入研究及开发利用提供重要的科学依据。更多还原

【Abstract】 Study areas were located in Nimu-Naqu high-temperature geothermal belt, in the Middle-North section of Dangxiong-Yangbajing-Duoqingcuo activity structure. Various high temperature geothermal manifestations were distributed in study area, there were rich in geothermal resources in Tibet. However, the geothermal field of Yangbajing and Yangyi have been investigated and researched systematically. In the paper, we choose11untapped geothermal fields along Nimu-Naqu in Tibet. Collected and gathered hydrochemistry, hydrogen and oxygen isotopes data, geothermal gases and its isotopes data in the study area, comparison of other typical high-temperature geothermal systems in Himalaya geothermal belt. It was significance to improve the genesis of high-temperature geothermal systems and provide guidance on exploration and drilling in the area. From the heat source, geothermal fluid migration pathways, geothermal fluid sources and thermal storage area features four aspects, this article reasearched typical high-temperature system, obtained the following understanding:High-temperature geothermal heat source system in the study area was generally considered to be partial melting of the crust layer contributions. It was obviously that active faults and deep tectonic activity controlled geothermal activity. There was a close relationship with surface rupture, seismic activities, geothermal distribution in Qinghai-Tibet Plateau hinterland; they were relationship with the deep geological processes that have genetic relationship dynamics.Analysis hydrochemistry of geothermal fluids, the chemistry type of high-temperature thermal water were mainly Cl-Na or CIHCO3-Na, moderate and high-temperature thermal water were mainly HC03-Na, there was a positive correlation Cl, Li, F, SiO2, HBO2with Cl, indicated possible mixing of magmatic water. With chemical geothermometer of thermal water and gas geothermometer, estimated the geothermal reservoir temperature were90to270℃; there were25%to75%cold water mixed with thermal water, estimated with chlorine and silicon enthalpy diagrams.From stable isotopes data, thermal water showed mainly meteoric recharge, thermal water presence slight "Oxygen-18drift" in Dongweng, Ningzhong high-temperature geothermal fields, the phenomenon was obvious in Gulu geothermal field than other geothermal fields; the tritium contents were less than1TU in Ningzhong, Gulu and Luoma, mainly sub-modern water recharge, Yuela was8.4TU, inferred to modern water recharge, others were mixed sub-modern with recent hybrid water recharge. Analysis carbon and sulfur stable isotopic characteristics of thermal water, revealed carbon and sulfur sources in thermal water mainly from leaching of the deposited layer, atmospheric source increased with cold water mixed, most of between the two types, part of material may from deep source.Geothermal gases were mainly carbon dioxide and nitrogen; there was a good negative correlation between carbon dioxide and nitrogen. From carbon isotopes from carbon dioxide, helium isotopes and comprehensive index analysis, the source of gases was mainly from crust, however, monitored R/Ra values greater than1in Ningzhong and Yuzhai, there may be a significant release of mantle material phenomena, the proportion of mantle helium was2.73%to30.93%.The studies showed that high-temperature geothermal systems primarily for heat and thermal water components contribute partial melting body, with geothermal fluids upward migration process, there have been mixed precipitation composition of the atmosphere; Helium isotope data of geothermal gases showed emplacement of mantle-derived substances in Ningzhong and Yuzhai geothermal fields.Finally, comprehensive analysis of regional geological data, deep exploration, mainly geothermal field geophysical results and the analyze results of geothermal fluid geochemical, obtained high-temperature geothermal field’s genesis model in the study area, and proposed conceptual model of Yuzhai high-temperature geothermal systems, for the latter depth research and development and utilization provided an important scientific basis.更多还原