鄂尔多斯盆地中西部延长组长6油层组物源分析

Provenance analysis of the Chang-6 pay sets of the Yanchang Formation in the west-central parts of the Ordos Basin

关键词:  上三叠统  延长组  物源分析  鄂尔多斯盆地

Key words:  Upper Triassic  Yanchang Formation  provenance analysis  Ordos Basin

摘要:

根据砂岩颗粒类型及特征、石英阴极发光、重矿物组合、砂体展布方向以及岩相古地理格局,对鄂尔多斯盆地中西部上三叠统延长组长6油组进行了物源分析。分析结果表明,酸性岩浆岩和中低级变质岩、浅海相碎屑岩及碳酸盐岩为研究区延长组主要的母岩类型,东北、西北、西部、西南和南部为5个主要的物源方向,且东北和西南影响范围最大;形成了东北安边三角洲沉积体系、西北盐定三角洲沉积体系、西部环县三角洲沉积体系、演武三角洲沉积体系、西南镇原辫状河三角洲沉积体系和南部固城-合水浊积扇沉积体系。

Abstract:

The types of the parent rocks and directions of sediment supply are discussed on the basis of the types and compositions of the sandstones,cathodoluinescence image of quartz,heavy mineral assemblages,sandstone distribution and palaeogeographic framework during the deposition of the Chang-6 pay sets of the Upper Triassic Yanchang Formation in the west-central parts of the Ordos Basin.The results of research in this study have disclosed that the parent rocks of the Yanchang Formation consist of acidic magmatic rocks,intermediateto low-grade metamorphic rocks and shallow-marine clastic rocks and carbonate rocks,and the principal sources of detritus lay to the northeast,northwest, west, southwest and south,especially the northeast and southwest. In these cases,there developed the deltaic depositional systems in Anbian in the northeast,Yanding in the northwest,Huanxian and Yanwu in the west;braided deltaic depositional systems in Zhenyuan in the southwest,and turbidite fan depositional systems in the Gucheng-Heshui region in the south.