柴达木盆地北缘新近系重矿物特征及物源分析

The Heavy Minerals Characteristics and Provenance Analysis of the Neogene in North Margin of Qaidam Basin

为了查明柴达木盆地北缘新近系物源方向、指导沉积相和砂体的展布的研究,在重矿物类型详细分析的基础上,应用数理统计及Q型聚类分析,对柴达木盆地北缘新近系碎屑岩的重矿物进行了矿物稳定性及其组合特征分析。研究表明新近系的重矿物以稳定矿物锆石、磁铁矿、白钛矿、石榴子石为主;而且稳定矿物含量大于非稳定矿物的含量,表明该区物源搬运距离较长,离物源区较远;并根据重矿物种类将研究区分为五大重矿物组合带。综合分析得出柴达木盆地北缘新近系存在三个物源方向:北西部阿尔金山物源区、小赛什腾山与赛什腾山物源区、东部的祁连山-绿梁山物源区。各物源方向为独立物源供给,但在冷湖地区则受到阿尔金山和小赛什腾山物源区两者的共同影响。柴北缘中部地区的物源供主要有有两个方向,阿尔金山物源,自西北向东南方向,可抵达鄂博梁Ⅱ号构造;赛什腾物源,自东北向西南方向,可抵达鄂博梁Ⅲ号构造。

With the Q-type cluster analysis and correlation analysis, to analysis the heavy minerals stability and non-stability coefficients and assemblage characteristics of the clastic rocks from the Neogene in the north margin of Qaidam Basin, the heavy mineral of the Neogene shows that the stability coefficients are relatively higher than the opposite, reflecting a long distance carrying away from the provenance systems. The type of heavy minerals and their combining forms are almost approaching in the all formations of the Neogenein the north margin of Qaidam Ba- sin. It shows that the provenance directions of the north margin of Qaidam Basin did not change significantly and has an inheritance relationship in the sedimentation process. A comprehensive analysis gets that mainly existed three provenance systems： the northwest provenance from A-erh-chin Mountains, Xiaosaishitengshan and Saishit- engshan, and the east provenance from Qilian Mountain and Ltiliangshan. Each of these provenances can divide in- to some smaller provenances and they are all relatively without intersected. But in the fourth and fifth Lenghu tec- tonic units has common effects both the provenance from the A-erh-chin Mountains and Xiaosaishitengshan.