鄂尔多斯盆地陇东地区长9油层组物源区分析

Provenance analysis of Chang 9 oil reservoir set in Longdong area,Ordos Basin

长9油层组沉积时期陇东地区可能存在多个物源供给区。物源分析是研究长9油层组三角洲发育特征的基础,也是对砂体进行评价和预测的依据。通过石英含量相对变化、重矿物组合特征、石英阴极发光分析、岩屑组分分析及古盐度恢复等研究发现,陇东地区同时受西南、西北、南部及东北等多个方向物源的影响和控制,其中主要物源来自陇东地区西南部,次要物源来自陇东地区南部、西北部和东北部。西南部主物源母岩为祁连构造带的中—高级变质岩与火山岩,南部、西北部和东北部次要物源分别来自南秦岭构造带、阿拉善古陆和阴山古陆的花岗岩及低—中级变质岩,以上几个方向的物源在元城—华池—马家砭—太白一带交汇。

There maybe exist multiple source supply during the sedimentation period of the Chang 9 oil reservoir set in Longdong area.Provenance analysis is not only the basis of study the delta development characteristics of Chang 9 oil reservoir set,but also the foundation for evaluation and prediction of sand bodies.Based on the relative change of quartz content,heavy mineral assemblages,quartz cathodoluminescence,debris content and paleosalinity recovery,it is considered that the deposition is controlled by the sources from the southwest,the northwest,the south and the northeast of Longdong area at the same time.The southwest of the study area is the main source area,followed by the south,the northwest and the northeast.The parent rocks in the southwest are middle-high grade metamorphics and volcanics in the Qilian tectonic belt,while the source in the south,the northwest and northeast is granite and low-middle grade metamorphics from the Southern Qinling tectonic belt,Alaschanica ancient land and Yinshan ancient land respective.The sediments that come from different directions converge at the area of Yuancheng-Huachi-Majiabian-Taibai.