鄂尔多斯盆地北部杭锦旗地区下石盒子组多物源体系:来自矿物学及碎屑锆石U-Pb年代学的证据

鄂尔多斯盆地北部上古生界砂岩碎屑组分、岩屑类型和重矿物组合具有明显的东西分带性,但是其物源来源及差异性尚不明确.利用锆石LA-ICP-MS U-Pb定年方法,对鄂尔多斯盆地北部杭锦旗地区下石盒子组碎屑锆石年龄分布及变化特征进行了研究,明确了不同年龄组分碎屑锆石的来源,并分析了不同物源体系及差异性.结果表明:不同地区下石...

Multiple Provenance System of Lower Shihezi Formation in Hangjinqi Area,Northern Ordos Basin: Evidence from Mineralogy and Detrital Zircon U-Pb Chronology

The detrital mineral contents,debris types and heavy mineral assemblages of Upper Paleozoic sandstone are obviously different from the east to west in the northern Ordos Basin.However,the provenance of sandstone still remains unclear.The distribution and variation characteristics of detrital zircon ages were studied using LA-ICP-MS dating of the detrital zircons from sandstones of Lower Shihezi Formation in the Hangjinqi area,Ordos Basin.The source of detrital zircons of different age components is identified,and difference of provenance system is analyzed.The main conclusions can be drawn as follows.Detrital mineral content of Lower Shihezi Formation is different in different regions,with quartz content decreasing and lithic fragment content increasing from west to east.Detrital zircons of Lower Shihezi Formation yield four peak ages of 280-340 Ma,400-450 Ma,1700-2000 Ma,and 2200-2500 Ma,and the proportion of Phanerozoic age of zircons gradually increases from east to west,with zircons having age range from 400 Ma to 450 Ma only appearing in the western and middle regions.By comparing the isotopic ages for the plutons in and around research areas,the sandstone of Lower Shihezi Formation in the western region mainly sourced from Alxa Block while in the middle and eastern regions mainly sourced from Daqingshan-Wulashan,Yinshan and Jining areas,and the provenance of middle region was also affected by Alax Block.Based on the difference of zircon ages,detrital mineral content and rock fragment component of Lower Shihezi Formation,it is believed that multiple provenance systems exist,which can be divided into western provenance,middle mixture provenance and northeast provenance in the Hangjinqi area.