渤海湾盆地北塘凹陷古近系沙河街组三段白云岩中方沸石的特征及成因

发布时间：2018-06-06 01:44

本文选题：白云岩 + 方沸石成因　；参考：《古地理学报》2017年02期

【摘要】：渤海湾盆地北塘凹陷古近系沙河街组三段白云岩中有多种矿物,X射线衍射(XRD)分析识别出的主要矿物有白云石、方沸石、石英、长石、黏土矿物、黄铁矿及方解石等,其中方沸石平均含量达38.8%。根据钻井岩心、岩石薄片、扫描电镜、电子探针和地球化学分析等资料,对沙三段白云岩中方沸石的矿物特征进行详细描述并探究其成因。结果表明,沙三段白云岩中的方沸石有2种分布样式,分别是纹层型和充填型,其中前者多与白云石互层、呈纹层状,偶见似结核状;后者形成较晚,方沸石以填隙物形式充填在裂缝、孔隙之中。这2种方沸石的存在形式、晶体形态、伴生矿物各不相同,其中纹层型方沸石多与白云石共生,晶体粒径小于0.04mm,为泥晶结构;充填型方沸石多与黄铁矿、有机质共生,晶体粒径大于0.04mm,为粉晶结构。根据主、微量元素及碳、氧同位素分析结果,计算出古盐度平均为28.8‰,Sr/Ba值平均为2.93,表明渤海湾盆地北塘凹陷沙河街组三段沉积时期为碱—咸溶液沉积环境,具备形成方沸石的条件。电子探针测试的Si/Al值表明,这2类方沸石母质来源不同,纹层型方沸石母质为黏土矿物,而充填型方沸石母质与热液有关。与国内含方沸石白云岩的盆地进行对比,并从岩石学特征、形成温度等方面进行分析,认为研究区方沸石有2种成因,其中纹层型方沸石是同生成岩阶段的产物,而充填型方沸石则受到热液流体的影响。
[Abstract]:There are a variety of minerals in the three segment of the Palaeogene Shahe Street formation in the Beitang sag, Bohai Bay basin. The main minerals identified by X ray diffraction (XRD) analysis are dolomite, zeolites, quartz, feldspar, clay minerals, pyrite and calcite. The average content of the zeolites is up to 38.8%. based on drilling core, rock thin slice, SEM, electron probe With the geochemical analysis and other data, the mineral characteristics of the Chinese zeolites in the three segment of the dolomite are described in detail and the causes are explored. The results show that there are 2 types of zeolites in the three segment of the dolomite of the sand, which are laminar and filling, the former is interbedded with dolomite, which is stratified and occasionally nodular; the latter is later formed. The zeolites are filled with fillings in the form of cracks and pores. The existence forms of the 2 kinds of zeolites, crystal morphology and associated minerals are different, in which the lamellar zeolite is mostly symbiotic with dolomite, and the grain size is less than 0.04mm and is a muddy crystal structure; the filling type zeolite is more than pyrite, organic matter is symbiotic and the crystal size is larger than 0.04mm and is powder. Structure. According to the results of the main, trace elements, carbon and oxygen isotope analysis, the average value of the paleo salinity is 28.8 per thousand and the average Sr/Ba value is 2.93. It shows that the three section of the Shahe Street formation in the Beitang sag of the Bohai Bay basin is the alkali salty solution sedimentary environment and the conditions for the formation of the zeolite. The Si/Al value of the electron probe test shows that the 2 kinds of the zeolite mother. The material source is different, the laminite parent material is clay mineral, and the filling type zeolite matrix is related to the hydrothermal fluid. Compared with the domestic zeolite dolomite basin, it is analyzed from the petrological characteristics and the formation temperature. It is believed that the zeolites in the study area have 2 causes, of which the laminite is the product of the same generation rock stage. And the filling type of zeolite is affected by hydrothermal fluid.
【作者单位】：南京大学内生金属矿床成矿机制研究国家重点实验室;莱斯大学地球科学系;中国地质大学(武汉)资源学院;金陵科技学院材料工程学院;
【分类号】：P578.974

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