Abstract: The analcime dolostone and its rock association were found in Dujiatai reservior of the Member 4 of Paleogene Shahejie Formation in Leijia area of western sag of Liaohe Depression, Bohai Bay Basin. These rocks have complex mineral assemblages and sedimentary structures, and were regarded as argillaceous dolostone and dolomitic mudstone association previously. Through integrated study of petrography,X-ray diffraction whole rock analysis,scanning electron microscope analysis and electron probe analysis, abundant sedimentary analcites in study area are discovered firstly, and are mixed with lamellar argillaceous dolomites, forming analcimite locally. Carbon and oxygen isotope analyses show that their δ¹³C value are positive while their δ¹⁸O value are negative,similar with those of the hydrothermal dolostones reported by domestic and foreign papers. The rare earth element patterns of the analcite dolostones are similar with the alkali basalts in the same layer and the lower Fangshenpao Formation. By synthesis analysis of these results, the formation of the analcite dolostone and the mineral transformation of the basalt in Fangshenpao Formation are closely related with lake floor hydrothermal process, and they form hydrothermal sedimentary rocks by interactions.

Key words: Shahejie Formation, Fe-bearing dolomite, analcite, geochemistry, hydrothermal sedimentary rock, Liaohe Depression

摘要： 渤海湾盆地辽河坳陷西部凹陷雷家地区古近系沙河街组四段杜家台油层发现方沸石白云岩及其组合类型。该套岩石具有复杂的矿物组分和沉积构造,以往被认为是一套泥质白云岩和白云质泥岩组合。利用岩石薄片鉴定、X衍射全岩分析、扫描电镜、电子探针等方法,首次发现该套岩石含有大量沉积成因方沸石,其呈纹层状与泥晶白云石混杂沉积,局部可成为方沸石岩。地球化学分析结果表明,该套岩石δ¹³C值偏正而 δ¹⁸O 值偏负,与已报道的热水白云石碳、氧同位素数据非常接近;稀土元素配分曲线特征与其同层位及其下伏房身泡组大套偏碱性玄武岩相似,具有很好的亲缘性。综合上述分析结果认为,方沸石白云岩的形成与房身泡组玄武岩的矿物转变以及湖底热液作用密切相关,为二者共同作用形成的热水沉积岩。

关键词: 沙河街组, 含铁白云石, 方沸石, 地球化学, 热水沉积岩, 辽河坳陷

CLC Number: 

• P588.24＋5

• P595