富县探区延长组微量元素特征及地质意义

Microelement and Geologic Significance of Yanchang formation in Fuxian Area, Ordos Basin

陕北的富县探区位于鄂尔多斯盆地的东南部,三叠系延长组发育了一套三角洲-湖泊相陆源碎屑含煤沉积建造。在延长组沉积期的沉积演化过程中,长10—长7油层组沉积期为湖盆扩张期,长6—长1油层组沉积期为湖盆收缩期。由于湖盆水体的性质及演化不但可提供盆地沉积演化的重要信息,而且它对湖盆三角洲的沉积作用也有着重要影响,因而了解沉积当时湖盆水体性质和气候条件对研究湖盆三角洲骨架砂体的成因类型及展布有重要意义。根据对富县探区延长组泥岩中微量元素的分析、研究,对晚三叠世延长组沉积期的湖盆水体性质、气候条件以及沉积作用等作出了分析、推断,为研究延长组砂体的成因及分布提供了佐证。

Fuxian area is located in southeastern part of Ordos basin where a set of delta-lacustrine terrigenous clastic sediments with coal is found in Yanchang formation of its Triassic system. During the process of sedimentation and evolution of Yanchang formation, Chang10-Chang7 members were characterized by lacustrine expansion, whereas Chang6-Chang1 members by lacustrine shrinkage. Since the character and evolution of the lacustrine water body could not only provide the important information of the basin's depositional evolution, but also it has the great influence on the sedimentation of the lacustrine-delta sand bodies. Based on the analyses of the microelecments obtained from the mudstones of Yanchang formation in Fuxian area, this paper makes study and prediction of the property of water body, palaeoclimate and sedimentation in period of Yanchang, which could be as a good supporting evidence for study of origin and distribution of the sand bodies in Yanchang formation.