鄂尔多斯盆地西南缘上奥陶统平凉组碎屑岩锆石U-Pb年龄及物源分析  

U-Pb Dating of Detrital Zircon from Upper Ordovician Pingliang Formation in Southwest Margin of the Ordos Basin and Provenance Analysis

作　　者：杨甫[1] 陈刚[1] 陈强[2] 丁超[3] 高磊[1] 雷盼盼[1] 张文龙[1] 师晓林[1] 童明军 

机构地区：[1]西北大学大陆动力学国家重点实验室/地质学系,西安710069 [2]长安大学地球科学与资源学院,西安710054 [3]西安石油大学地球科学与工程学院,西安710065 [4]陕西延长石油国际勘探开发工程有限公司,西安710075

出　　处：《地质论评》2015年第1期172-182,共11页Geological Review

基　　金：西北大学大陆动力学国家重点实验室科技部专项经费(编号:BJ14252);国家自然科学基金(编号41172101);中国地质调查局油气资源项目(编号1212011220761);国家基础科学人才培养基金(编号XDCX2014-18)资助的成果

摘　　要：运用碎屑锆石LA-ICP-MS U-Pb年代学分析方法,探讨分析了鄂尔多斯地块西南缘奥陶系平凉组沉积期的物源环境。结果表明：①平凉组凝灰质砂岩中的碎屑锆石U-Pb年龄大致包含3组：第一组为早古生代的407~477Ma,峰值为454Ma,占总体的72.5%;第二组为中—新元古代的588~1548Ma,峰值为962Ma,占总体的22.5%;第三组为古元古代的1612~2496Ma,占总体的5%。②集中在407~477Ma年龄组分指示其物源主要来自于祁连—北秦岭岛弧杂岩带,588~1548Ma和1612~2496Ma的年龄组分反映的物源主要来自于北秦岭造山带,祁连造山带和华北板块基底。③锆石年龄谱综合分析,平凉组碎屑沉积物质来源复杂,具有明显的多源性,指示晚奥陶世平凉期的沉积环境应属于祁连—北秦岭岛弧杂岩带与鄂尔多斯地块西南缘之间的局限残留边缘海盆地。The U-Pb ages of single zircon grains contained in the sandstone samples were analyzed by the LA- ICP-MS method, the sediment provenances and geological significance were discussed. The results show that： ① The detrital zircon age of the tuffaceous sandstone from the Upper Ordovician Pingliang Formation can be obviously divided into three groups, the first group is Early Paleozoic which ranges from 407 ~477Ma, the peak value is 454Ma, accounting for about 72.5% of the total dates. The second group is Meso--Neoproterozoie which ranges from 588 - 1548Ma, the peak value is 962Ma, accounting for about 22.5% of the total dates. The last group is Paleoproterozoic which ranges from 1612 ~ 2496Ma, accounting for about 5% of the total dates. ② The group of 407 ~477Ma indicates that its material provenances may mainly come from the North Qinling--Qilian island-arc complex belt in adjacent regions. The group between 588 - 1548Ma and 1612 - 2496Ma indicates that its material provenances were mainly from the Noah Qinling orogenic belt and the Qilian orogenic belt, with the little of material from the basement of North China block.③ A comprehensive analysis shows that the material provenances of Pingliang Formation were much more complicated and characterized by obvious diversity and complexity. The indication is that sedimentary environment is the limits of residual marginal sea basin between North Qinling-- Qilian island-arc complex belt and the southwest of Ordos block in the Pingliang age Ordovieian.

关 键 词：上奥陶统平凉组 锆石LA-ICP-MS U-PB定年 物源分析 鄂尔多斯盆地 

分 类 号：P588.21[天文地球—岩石学] P597.3[天文地球—地质学]