内蒙古扎鲁特地区上二叠统林西组古盐度分析

通过对扎鲁特地区陶海营子剖面和鲁D2井泥岩样品中微量、常量元素和黏土矿物的测定,利用Adams和Couch古盐度计算公式及Walker相当硼判定法、锶钡比值法、硼镓比值法、生物标记化合物等方法,综合分析了扎鲁特地区林西组沉积时水体的古盐度特征.结果表明,鲁D2井林西组沉积时为半咸水环境,陶海营子剖面林西组则为淡水环境,扎鲁特地区林西组沉积时期水体环境有一个逐渐淡化的过程,下部为半咸水的湖泊环境,上部逐渐演化为淡水湖泊环境.半咸化的湖水环境为林西组巨厚层烃源岩的发育提供了有利条件.

ANALYSIS ON THE PALEOSALINITY OF UPPER PERMIAN LINXI FORMATION IN JARUD AREA,INNER MONGOLIA

Based on the determination of trace elements,major elements and clay minerals in the mudstone samples from the Taohaiyingzi section and Lu-D2 well in Jarud area,the Adams＇s and Couch＇s paleosalinity formulas are adopted,along with the decision methods of ＂equivalent boron＂ by Walker,Sr-Ba ratio,B-Ga ratio and biomarkers,to synthetically analyze the water salinity characteristics corresponding to the sedimentary period of Linxi Formation in Jarud area.The results show that the Linxi Formation at Lu-D2 well formed in brackish-water environment; while that at the Taohaiyingzi section,in freshwater environment.Furthermore,the water salinity appeared the decreasing trend in the sedimentary period of Linxi Formation in Jarud area.To be specific,the lower part strata corresponded to the brackish-water lake environment,while the upper part strata corresponded to the freshwater lake environment.Above all,the brackish-water lake environment could provide the favorable condition for developing thick source rock.