同位素演化对固市凹陷地下热水成因分类及渭河断裂导水性的指示意义

发布时间：2018-06-26 03:56

本文选题：固市凹陷 + 地下热水　；参考：《长安大学》2016年硕士论文

【摘要】：同位素水文地球化学方法在研究地下热水的起源成因及赋存特征方面具有不可替代的优势。本文以固市凹陷和渭河断裂周边地下热水为研究对象,在野外实地取样调查及同位素测试分析的基础上,系统的研究了固市凹陷地下热水特征和渭河断裂导水机理。研究成果既可丰富对地下热水深循环理论的认识又为固市凹陷与渭河断裂相关的咸阳西安关中城市群带地热资源开发利用提供科学依据。固市凹陷地下热水的δD和δ18O同位素研究表明:固市凹陷地下热水在不同次级构造单元具有不同的赋存特征及不同的补给来源。13C同位素表明地下热水中HCO3-并非是气源或幔源成因而是来自碳酸盐溶解。δ13C与HCO3-的关系提示固市凹陷地下热水赋存封闭程度固市断凹二华断阶三原断阶。δ34S揭示固市凹陷热下热水可能经历了由大气降水补给的开放状态到封闭滞留状态的过程。固市凹陷地下热水水文地球化学特征研究表明:固市凹陷地下热水普遍发生了溶滤、混合、脱碳酸、阳离子交替吸附作用,且固市断凹地下热水的TDS为固市凹陷之最。同位素及水文地球化学演化特征揭示,三原断阶地下热水的补给来源为北东方向庙山大气降水,二华断阶地下热水主要受西南方向少华山古代大气降水补给,固市断凹地下热水是与关中盆地同时沉积形成的沉积水或残存沉积水。渭河断裂周边地下热水在沿断裂走向从西到东水化学类型从SO4-Na型演变为SO4-Cl-Na型,TDS逐渐升高,结合氘氧及锶同位素表明渭河断裂在沿断裂走向上具有明显的导水性。而渭河断裂南北两侧地下热水水化学类型、氘氧同位素富集程度、锶同位素含量、地下热水年龄均有较大差异,表明渭河断裂垂直断裂走向上水力联系不明显。渭河断裂周边地下热水与附近非断裂带地下热水相比具有更高的温度和循环深度,氘氧同位素研究表明断裂带地下热水混入了当地承压冷水,说明渭河断裂在铅垂方向上具有较好的导水性。渭河断裂对关中盆地腹部地下热水的形成、赋存有重要影响。
[Abstract]:Isotopic hydrogeochemical method has an irreplaceable advantage in studying the origin and occurrence characteristics of geothermal water. On the basis of field sampling and isotopic analysis, the characteristics of underground hot water and the mechanism of water conductivity of Weihe fault in Gushi sag are systematically studied in this paper, taking the geothermal water around Gushi sag and Weihe fault as the research object, and on the basis of field sampling and isotopic analysis. The research results can not only enrich the understanding of the theory of deep circulation of underground hot water, but also provide scientific basis for the exploitation and utilization of geothermal resources in Guanzhong urban agglomeration belt of Xi'an, Xianyang, which is related to Weihe fault. The 未 D and 未 18O isotopic studies of geothermal water in Gushi sag show that the geothermal water in Gushi sag has different occurrence characteristics and different recharge sources in different secondary tectonic units. 13C isotope shows that HCO _ 3- in geothermal water is not gas. The relationship between 未 13C and HCO _ 3- indicates that the geothermal water in Gushi sag is closed. 未 34S reveals that the hot water in Gushi sag may have experienced precipitation from the atmosphere. The process from an open state of recharge to a closed state of detention. The hydrogeochemical characteristics of geothermal water in Gushi sag show that dissolved filtration, mixing, decarbonation, cation alternate adsorption are common in the geothermal water of Gushi depression, and TDs of the geothermal water in Gushi fault depression is the most common in Gushi sag. The characteristics of isotopic and hydrogeochemical evolution reveal that the recharge of underground hot water in Sanyuan fault terrace is from Miaoshan atmospheric precipitation in the north east direction, and the geothermal water in the Erhua fault terrace is mainly recharged by the ancient precipitation in the southwest Shaohua Mountains. Gushi fault depression geothermal water is sedimentary water or residual sedimentary water formed at the same time as Guanzhong basin. The underground hot water along the Weihe fault zone evolved from so _ 4-Na type to so _ 4-Cl-Na type TDs along the fault strike. The combination of deuterium and oxygen and strontium isotope shows that the Weihe fault has obvious conductivity along the fault strike. However, the hydrochemical types, enrichment degree of deuterium and oxygen isotopes, strontium isotopic content and age of underground hot water on the north and south sides of Weihe fault are quite different, which indicates that the vertical strike of Weihe fault has no obvious hydraulic connection. The geothermal water around the Weihe fault has a higher temperature and cycle depth than that in the nearby non-fault zone. Deuterium and oxygen isotopic studies show that the geothermal water in the fault zone is mixed with local confined cold water. It shows that the Weihe fault has good water conductivity in the vertical direction. Weihe fault has an important influence on the formation and occurrence of underground hot water in the central part of Guanzhong Basin.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P314.1;P642.2

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