鄂尔多斯盆地西南缘二叠系山西组山1段-下石盒子组盒8段物源分析

针对鄂尔多斯盆地西南部上古生界山1段与盒8段沉积物来源以及这两个层段物源是否发生改变等问题，依据物源分析方法，对研究区古水流特征、重矿物特征、镜下长石、岩屑特征以及稀土元素特征进行系统分析。通过古水流特征可初步判断研究区山1段与盒8段为多物源；重矿物组合可将研究区盒8段分为四个区域，分别为研究区北部，西南，东南和中部，且根据锆石和白钛矿的含量又可将研究区北部分出两个小的区域；沉积物碎屑以及稀土元素等特征反映出研究区北部具有远源沉积的特征，南部具有近源沉积的特征；山1段物源与盒8段物源分析结果比较类似。综合以上分析结果得出:山1段时期，盆地北部的阴山古陆为研究区北部提供沉积物来源；研究区西南部沉积物质来源于西秦岭与祁连山古陆的中北部；东南部地层沉积物来源于盆地南缘的北秦岭地区，汇水区位于环县、华池一带；盒8段时期阴山古陆继续为本次研究区北部提供碎屑沉积物，研究区西南部碎屑沉积物来自当时的祁连古陆的中北部盒秦岭古陆的西部，东南部物源来自北秦岭古陆，沉积物交汇区同样位于环县、华池一带；山1与盒8两个时期的沉积物物源没有发生改变，二者沉积物源具有继承性；另外根据REE特征，可判断出沉积时期除汇水区地势较低外，研究区东南部也存在一处规模较小的洼陷。

Provenance Analysis of Permain Shan1 and He 8 Formation in Permian in Southwest Ordos Basin

Since there are little provenance documents about Permian of southwest Ordos Basin,this paper focuses on the provenance analysis of Permain Shan 1 and He 8 Formation in Permian to figure out provenance of the two forma-tions and whether there are differences between these two contiguous formation. Based on provenance analysis meth-ods,the characteristics of paleocurrent,heavy mineral,feldspar,fragments,and REE have been analyzed.The result will benefit for the prediction of favorable reservoir. The character of paleocurrent shows that the provenance of Permi-an in the southwest Ordos Basin is multiplied,and we can divide He 8 formation into four parts based on the combina-tion of heavy mineral:the north,southwest,southeast and the middle part of the study area. Besides the north study area can be divided into two parts based on the content of zircon and leucosphenite,the provenance of this two parts are the northwest and the northeast of Yin mountain divided by Ural mountains;The character of fragments and REE reflect that the north of study area have the character of distant deposition and the south of study area are close deposi-tion. The provenance characters of Shan 1 and He 8 Formation are very similar. The information above draw the con-clusion that in the study area the deposition in the north part of Shan1 Formation came from the Yin Mountains in the north of the basin, the southwest part from the middle north of Qilian Mountains and west Qinling Mountains and southeast part from the north Qinling Mountains in the south of the basin. And the sediment came across around Hua-nxian and Huachi.The provenance of He 8 Formation is similar to Shan1 Formation,the sediments in north part of the study area is from Yin Mountains in the north of Ordos basin;The middle east of Qilian Mountain and west Qinling Mountain provide sediments for southwest of study area,the provenance of southeast part of the study area is north Qin-ling Mountain in the south of the basin and the catchment area is also around Huanxian and Huachi. Results show that the provenance of the two formations did not change so much and the two formations have the character of succession. Besides The characters of REE shows that there are two locations in the study area have a lower altitude which shows a reducing environment.