四川盆地川东三叠系（含盐系）及卤水地球化学特征研究

发布时间：2018-05-29 06:30

本文选题：杂卤石 + 溴氯系数　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：我国是目前世界上最大的钾肥消费国家,但钾肥资源的储备在中国缺乏,很难满足农业的需求。四川盆地三叠纪是中国重要的成盐盆地,以前的探索发现三叠纪嘉陵江组和雷口坡组有厚达千米的含盐系。除了大量的盐和混合卤化物,还发现有钾明矾石及钾镁盐等,说明了该地区有较好的成钾条件。本论文依托于中国地质科学院矿产资源研究所973项目“中国陆块海相成钾规律及预测研究”第二课题“四川三叠纪古特提斯海盆成钾条件、机理和后期演化”,主要对四川盆地长平三井含盐系钻井岩心及四川盆地内的卤水样品进行了岩石学,矿物学,地球化学和氢、氧同位素等方面的研究,并结合前人的研究资料,初步尝试探讨了这些实物资料揭示的成盐成钾条件。通过钻孔编录分析,将长平三井含盐系分为自上而下的三个成盐沉积旋回。反复的海进和海退现象在该套地层的沉积过程中时常伴随,使得原始水体的浓度发生反复变化。长平三井含盐系包含有三个主要的含盐层位,盐层累计厚度达到52.37m。其含盐系主要矿物有石盐、硬石膏、杂卤石、白云石、方解石等,通过对杂卤石的鉴定分析,认为其中的微粒状杂卤石,主要呈薄层状集合体分布于石盐中,为水体在发生蒸发浓缩时原生析出形成;蕉叶状或短柱状杂卤石多为单体颗粒,为水体早期蒸发浓缩的成盐过程中经过重结晶作用而形成。通过对长平三井含盐系地球化学溴氯系数的研究,发现长平三井含盐系溴氯系数普遍较高,部分层位溴氯系数值显示已达钾镁盐的析出阶段。并有来自盆地内或其他次级盆地的浓卤水的补给发生在各个盐层的沉积起始阶段。通过对四川盆地内三叠系卤水样品的地球化学分析,发现卤水主要成分为Na Cl,大多数样品显示较贫Ca2+、Mg2+和SO42-。其中,有4个样品的K含量较高,已达开采及工业生产利用的经济价值。对卤水样品氢、氧同位素的分析,认为卤水的成因绝大多数属于海相沉积-大气降水叠加型,其成因既与大气降水的渗入有关,同时也与海水的补给有关,并有较为活跃的水-岩交换作用的伴随。
[Abstract]:China is the largest potash consumption country in the world at present, but the reserve of potash fertilizer resources is scarce in China, so it is difficult to meet the demand of agriculture. The Triassic of Sichuan Basin is an important salt-forming basin in China. Previous explorations have found that the Jialingjiang formation and the Leikoupo formation of Triassic have a salt bearing series of km thick. In addition to a large amount of salt and mixed halides, potassium alunite and potassium magnesium salts are found, which indicates that there are better conditions for potassium formation in this area. This paper is based on the project 973 of the Institute of Mineral Resources of the Chinese Academy of Geological Sciences, "study on the regularity and prediction of the formation of potassium from land blocks and seas in China", the second topic, "conditions, mechanisms and late evolution of the Triassic Paleotertes basin in Sichuan Province". In this paper, petrology, mineralogy, geochemistry and hydrogen and oxygen isotopes were studied in the core of the salt bearing well of Changping well No. 3 in Sichuan Basin and the brine samples in Sichuan Basin. The conditions of salt forming and potassium formation revealed by these physical data were preliminarily discussed. Through the analysis of borehole cataloguing, the salt bearing system of Changping Sanjing is divided into three salt forming cycles from top to bottom. The repeated transgression and regression phenomena are often accompanied by the sedimentary process of this set of strata, which makes the concentration of the original water body change repeatedly. The salt bearing system of Changping Sanjing has three main salt-bearing beds, and the accumulative thickness of the salt beds is 52.37 m. The main minerals of the salt bearing series are stone salt, anhydrite, heterohalite, dolomite, calcite and so on. Through the identification and analysis of the heterohalite, it is considered that the microgranular heterohalide is mainly distributed in the salt as a thin layer aggregate. It is suggested that the primary precipitate is formed when the water body evaporates and condensed, and the banana leaf or short columnar heterohalite is formed by recrystallization during the salt forming process of evaporation and concentration in the early stage of evaporation and concentration of water body, most of which are monomeric particles. Based on the study of the geochemical bromochlorine coefficient of salt bearing series in Changping Sanjing well, it is found that the bromine chlorine coefficient of salt bearing system in Changping Sanjing well is generally high, and the bromine chlorine coefficient value of some layers indicates that the precipitation stage of potassium and magnesium salt has been reached. The recharge of the concentrated brine from the basin or other secondary basins occurs at the sedimentary initiation stage of each salt bed. Based on the geochemical analysis of Triassic brine samples in Sichuan Basin, it is found that the main component of brine is NaCl, and most of the samples show poor Ca2 Mg2 and SO42-. Among them, four samples have high K content, which has reached the economic value of mining and industrial production. Based on the analysis of hydrogen and oxygen isotopes of brine samples, it is concluded that the origin of brine is mostly marine sedimentation-atmospheric precipitation superposition type, which is related to the infiltration of atmospheric precipitation and the recharge of sea water at the same time. And there is a more active water-rock exchange with.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P619.211

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