四川盆地中下三叠统盐卤水水文地球化学特征及成因研究

发布时间：2018-05-29 08:08

本文选题：四川盆地 + 中下三叠统　；参考：《成都理工大学》2015年硕士论文

【摘要】：随着中国经济的快速发展,钾盐资源的需求增大,在中国的各大沉积盆地陆续都展开了钾盐资源勘探工作。四川盆地作为我国重要的沉积盆地,卤水资源丰富,特别是在三叠系地层中发现了富钾卤水,极具开发利用价值。本文研究四川盆地中下三叠统盐卤水的水文地球化学特征,总结了四川盆地的演化历史以及三叠系地层岩性,地质构造等水文地质条件,分析了四川盆地中下三叠统盐卤水水化学组成,矿化度及水化学常规组分的分布特征,并按照四川盆地三叠系含水层的水文地质条件差异,将其分成了多个区域,分析了各区的水化学组成,离子比例系数,并同海水蒸发各阶段的海水水化学组成对比。然后,对四川盆地部分盐卤水的氢氧、硫、硼同位素和气体组分的特征进行了分析。最后,追溯盐卤水的演化过程,讨论了不同的水文地球化学过程对盐卤水成分的影响。主要取得了以下几点认识:1、四川盆地为一个多岩层平行叠置的自流水盆地,自上而下可以分成多个含水层,中下三叠系地层作为其中一个主要的含水层,大部分深埋盆地腹地,含水层的边界受到区域断裂控制,含水层的岩性以碳酸盐类为主,在嘉陵江和雷口坡组中地层有多个稳定的储卤层。2、四川盆地中下三叠统盐卤水的矿化度差异较大,常量组分以Cl-、Na+为主,SO42-与HCO3-含量较低,部分微量含量较高,水化学类型以Cl-Na型水主。对盆地内不同区域中下三叠统地层中盐卤水水化学组分对比分析发现,川北、川西的盐卤水矿化度、Cl-和Na+含量较高;川南与川东的SO42-的含量较高;盆地内Mg2+、HCO3-的含量都很低,盆地内各区差异不大;川北和川中的Ca2+含量较高;川西和川东北部分K+含量异常高。3、通过水化学组分相关性分析发现,四川盆地中下三叠统盐卤水的矿化度与Cl-、Na+的相关性良好,而与HCO3-相关性较差,与SO42-呈现负相关。R型聚类分析表明,川西,川北、川西南地区的盐卤水具有相似的水化学成因。因子分析的结果表明,对研究区盐卤水水化学成分影响最大的是石盐、钾盐以及方解石和白云石的溶滤作用。对研究区盐卤水离子比例系数分析表明,各区卤水都显示了溶滤水的特征,川西、川中、川东北地区的盐卤水储层封闭程度较好,后期伴有强烈的变质作用。根据离子比例系数的Q型聚类分析表明,川西和川中的盐卤水的成因较为类似,而与盆地其他地区如川东和川南的成因差异较大。4、同海水蒸发浓度各阶段的海水水化学组分对比发现,研究区盐卤水的Na+、Cl-、K+随矿化度变化与海水蒸发类似,说明盐卤水同海相沉积关系密切,Mg2+的含量较海水蒸发同期低,Ca2+的含量较海水蒸发同期高,说明在卤水演化过程中发生了白云岩化作用和阳离子交换作用,SO42-含量较海水蒸发同期低,这是由于厌氧细菌通过生物化学作用将SO42-分解成为H2S所致。5、研究区盐卤水δD值为㧟7~㧟46‰,δ18O值为+1‰~+8‰,d值为㧟31~㧟66‰,其氢氧同位素组分接近原始海水,后期演化过程中受蒸发、地表水补给和周围石膏脱出的结晶水的影响,造成氢同位素组成略低于海水,水岩交换作用导致氧同位素组成偏高。研究区盐卤水δ34S的值为㧟15~㧟37‰,硫同位素与同层的硬石膏具有同源性,川25井的δ34S值异常高,反应了极强的生物化学作用。6、研究区盐卤水方解石、白云石大多处于饱和状态,石膏、岩盐以及钾盐处于未饱和状态,反向模拟实验结果表明,形成富钾卤水需要溶滤富钾矿物。研究区盐卤水的演化可以概括为三个阶段。沉积水形成阶段:原始沉积水多源自海水,当时盆地内海水浓度程度普遍到达了泻利盐沉积阶段。封闭埋藏阶段:川南部分地区由于构造隆起,其沉积水受到了大气降水的淋滤的影响,盆地大部分地区沉积水都受到了相邻岩层石膏脱水以及白云岩化的阳离子改造作用的影响。后期改造阶段:部分构造作用强烈区域的盐卤水溶滤相邻盐层的富钾矿物形成了富钾卤水。
[Abstract]:With the rapid development of China's economy and the increasing demand for potash resources, the exploration of potash resources has been carried out in the major sedimentary basins in China. As an important sedimentary basin in China, the Sichuan basin is rich in brine resources, especially in the Triassic strata, which has great potential for exploitation and utilization. This paper studies the Sichuan basin. The hydrogeochemical characteristics of the salt brine in the middle and lower three strata of the middle and lower strata, summarized the evolution history of the Sichuan basin and the hydrogeological conditions of the Triassic stratum lithology and geological structure, and analyzed the chemical composition of the salt brine water in the middle and lower middle three series of the Sichuan Basin, the mineralizing degree and the distribution characteristics of the conventional components of the hydrochemistry, and according to the Triassic water cut in the Sichuan basin. The hydrogeological conditions of the layer are divided into several regions, and the hydrochemical composition, the ion ratio coefficient and the chemical composition of the sea water in each stage of the seawater evaporation are analyzed. Then, the characteristics of the hydrogen, oxygen, sulfur, boron isotopes and the gas composition of the salt brine in the Sichuan basin are analyzed. Finally, the salt brine is traced. The evolution process has discussed the effects of different hydrogeochemical processes on the composition of salt brine. 1, the Sichuan basin is a parallel stacked self flowing basin with multiple strata, which can be divided into several aquifers from top to bottom, and the middle and lower Triassic strata are one of the main aquifers and most of the deep buried basins. In the hinterland, the boundary of aquifers is controlled by regional fracture, and the lithology of aquifers is dominated by carbonate. In the Jialing River and Lei Kou Poe formation, there are many stable halogen layers.2. The salinity of salt brine in the middle and lower three halides of the Sichuan basin is different, the component of the permanent component is Cl-, Na+ is the main, the content of SO42- and HCO3- is lower, and some trace content is high. The hydrochemical type is Cl-Na type water main. The comparison and analysis of the chemical composition of salt brine water in the middle and lower three strata of different regions in the basin shows that the salinity of salt brine, Cl- and Na+ content in the North Sichuan and Western Sichuan are higher; the content of SO42- in South and East Sichuan is higher; the content of Mg2+, HCO3- in the basin is very low, and the differences in each region in the basin are not very different; North Sichuan and Sichuan The content of Ca2+ in the Western Sichuan and northeastern Sichuan is very high, and the content of K+ is very high.3. Through the correlation analysis of hydrochemical components, it is found that the salinity of the salt brine in the middle and lower middle three series of the Sichuan basin is well correlated with Cl- and Na+, but the correlation with HCO3- is poor, and the negative correlation.R type cluster analysis with SO42- shows that the salt brine in Western Sichuan, North Sichuan and southwest Sichuan. Water has similar hydrochemical causes. The result of factor analysis shows that the greatest influence on the chemical composition of salt brine water in the study area is the dissolution and filtration of calcite and calcite and dolomite. The analysis of the ratio coefficient of the salt brine ions in the study area shows that the brine in the region shows the characteristics of the water soluble and filtration water, in Western Sichuan, in Sichuan and Northeast Sichuan. The salt brine reservoir has a better sealing degree and later strong metamorphism. According to the Q cluster analysis of the ion ratio coefficient, the cause of the salt brine in the Western Sichuan and Sichuan is similar, but the difference from the other parts of the basin, such as East Sichuan and South Sichuan, is larger than that of.4, and the comparison of the chemical composition of seawater hydrochemical components at each stage of the evaporation concentration in the sea water is found. The change of Na+, Cl- and K+ with salinity in the salt brine of the study area is similar to that of seawater evaporation, indicating that the salt brine is closely related to the marine deposition, the content of Mg2+ is lower than that of the evaporation at the same period in the sea water, and the content of Ca2+ is higher than that of the evaporation at the same period in the sea water. It shows that the dolomitization and cation exchange of the brine have occurred in the process of the evolution of the brine, and the content of SO42- is more evaporation than the evaporation of the sea water. The same period is low, because anaerobic bacteria decompose SO42- into.5 caused by H2S by biochemical action. The delta D value of the salt brine in the study area is 7~? 46 per thousand, the value of delta 18O is +1 per thousand ~+8 per thousand, D value is 31~? 66 per thousand, and its hydrogen and oxygen isotopes are close to the original sea water, and the effect of evaporation, surface water supply and the effect of the crystalline water out of the surrounding gypsum during the later evolution process The composition of hydrogen isotopes is slightly lower than that of sea water, and the oxygen isotope composition of the water and rock exchange results in high oxygen isotope composition. The value of the salt water delta 34S is 15~? 37 per thousand, the sulfur isotope is homologous to the anhydrite of the same layer, the delta 34S value of the 25 well in Sichuan is very high, which reacts the very strong biochemical action of the salt brine, and the salt brine calcite in the study area is mostly in the dolomite. The saturated state, gypsum, rock salt and potassium salt are in the unsaturation state. The results of the reverse simulation experiment show that the formation of potassium rich brine needs to be dissolved in the potassium rich mineral. The evolution of salt brine in the study area can be summarized as three stages. The formation stage of the sedimentation water is that the original sedimentary water is mainly from the sea water, and the degree of seawater concentration in the basin generally reached the salting salt at that time. The sedimentary stage, closed burial stage: due to tectonic uplift in some parts of South Sichuan, its sedimentation is affected by the leaching of atmospheric precipitation, and the sedimentary water in most of the basin is affected by the cation transformation of gypsum dehydration and dolomitization of the adjacent rock strata. Water - soluble potassium rich minerals from adjacent salt beds form potassium rich brines.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P619.211

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