白垩纪以来库车坳陷碎屑重矿物组成变化

碎屑沉积是山脉隆升和盆地沉积的直接记录,包括碎屑重矿物研究在内的碎屑沉积物的分析是开展盆山耦合研究的必要手段。本文对库车坳陷白垩系—新近系砂岩中重矿物含量特征进行了系统的研究,并应用电子探针技术分析碎屑石榴石和电气石的化学组成。研究表明:库车坳陷白垩-新近系源区主要由高级变质岩和沉积岩以及中-酸性火成岩组成。白垩纪和古近纪砂岩中的石榴石富钙镁铝榴石组份,与来自西南天山低温高压变质岩中石榴石组成相似,而新近系砂岩中的石榴石中富铁铝榴石组份,多来自高级变质沉积岩,而非高压变质岩。这些分析表明南天山的大规模隆升和剥蚀发生在渐新世以来,由于它的隆升遮挡了西南天山对库车坳陷的物质贡献。

CHANGES OF DETRITAL HEAVY MINERALS' COMPOSITION IN THE KUQA DEPRESSION FROM CRETACEOUS

Detritus sediment is a direct record of mountain uplifting and basin subsidence. The analysis of detritus sediment,including heavy minerals,is necessary means for basin-mountain coupling study.The contents of heavy minerals in the Cretaceous,Paleogene and Neogene from the Kuqa Depression were studied systemically in this paper,and the geochemical compositions of detrital garnets and tourmalines were analysed by electric probe.The results showed that the provenances of the Cretaceous,Paleogene and Neogene in the Kuqa Depression were mainly composed of high-grade metamorphic rocks,sedimentary rocks and intermediate-acid igneous rocks.The composition of garnets in the Cretaceous and Paleogene sandstones was similar with those in low temperature and high pressure metamorphic rocks from the South Tianshan.The garnets from Neogene were rich in almandine,which mainly come from meta-sedimenatry rocks in the South Tianshan.Based on these results,it could be suggested that there might be a large scale uplift and erosion in the South Tianshan from Neogene,which sheltered the contributions of high-pressure metamorphic rocks in the South Tianshan to the Kuqa Depression.