柴达木盆地古近系路乐河组重矿物特征与物源分析

柴达木盆地古近系路乐河组由于其沉积演化与青藏高原隆升密切相关,并且近几年来多口探井在该层系见到了良好的油气显示而被研究者所关注.沉积物源分析作为了解造山带构造演化、盆地沉积作用以及划分油气有利区带的重要方法是路乐河组研究的关键内容.前人对盆地不同区块第三系物源进行了研究但缺乏从全盆地范围整体探讨路乐河组物源的报导.本次研究通过重矿物组合、ZTR指数及重矿物稳定系数的平面展布特征结合岩屑类型对柴达木盆地古近系路乐河组地层进行系统分析,初步划分出昆特依-冷湖一-四号、马海-南八仙、红山、鄂博梁-碱山、油砂山-跃进、黄石-弯西等11个物源体系,基本确定了物源方向并恢复了母岩类型.研究表明,不同物源区沉积物特征差异较为明显,表现为昆仑山前物源搬运距离最长,阿尔金山前物源搬运距离最短,祁连山前物源搬运距离中等.上述认识为研究区沉积体系的精细划分、原型盆地恢复以及盆地构造演化提供了重要依据.

Heavy mineral feature and provenance analysis of Paleogene Lulehe Formation in Qaidam Basin

Many scholars are focusing on Paleogene Lulehe Formation of the Qaidam Basin as its sedimentary evolution is closely related to the uplift of Tibet Plateau and it has seen well evidences of oil and gas in recent years. The provenance analysis as an important method of understanding the orogenic belt evolution, the basin sedimentation and dividing the oil-gas favorable zone has become the key elements of researching Lulehe Formation. Former study about the tertiary sediment provenance analysis of Qaidam Basin were from different regions and strata of the basin but not included the Lulehe Formation from the whole basin scale. This study has a system analysis of the Paleogene Lulehe Formation in Qaidam Basin, which combined by the heavy mineral assemblage, distributional characteristics of the ZTR index and the stability factor in plane and the types of lithic fragment. We initially divide Lulehe Formation into 11 sediment provenance systems containing Kunteyi-Lenghu No.1~4, Mahai-Nanbaxian, Hongshan, Eboliang-Jianshan, Youshashan-Yuejin, Huangshi-Wanxi, etc. And we basically determine the source direction and the types of the parent rocks. The results show that characteristics of sediments are obvious differences in different source areas, indicating the sediments from the Kunlun Mountain has the longest transport distance, Altun Mountain has the shortest transport distance and Qilian Mountain has the medium transport distance. The understanding mentioned above provides the foundation for the fine division of provenance system in the study area, the restoration of prototype basin as well as basin tectonic evolution.