鄂尔多斯盆地西北缘晚三叠世早期物源组成——来自碎屑锆石U-Pb年龄的指示  

Provenance Composition of the Early Late Triassic,Northwestern Ordos Basin:Indications from Detrital Zircon U-Pb Ages

作　　者：雷琳琳 赵红格[1] 邵晓州[2] 徐智[2] 郭惠 李亚男[1] 付星辉 李蒙[1] LEI LinLin;ZHAO HongGe;SHAO XiaoZhou;XU Zhi;GUO Hui;LI YaNan;FU XingHui;LI Meng(Geology Department/State Key Laboratory of Continental Dynamics,Northwest University,Xi’an 710069,China;Exploration and Development Research Institute,PetroChina Changqing Oilfield Company,Xi’an 710021,China;Jiangsu Suyan Jingshen Co.,Ltd,Huaian,Jiangsu 223200,China)

机构地区：[1]大陆动力学国家重点实验室/西北大学地质学系,西安710069 [2]中国石油长庆油田勘探开发研究院,西安710021 [3]江苏苏盐井神股份有限公司,江苏淮安223200

出　　处：《沉积学报》2020年第6期1258-1271,共14页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41330315,40902032);大陆动力学国家重点实验室团队项目(201210132);陕西省高校青年创新团队(盆地演化与能源矿产)项目;长庆油田5000万吨重大专项(2016E-0514);长庆油田科技项目(技2019-77)。

摘　　要：利用碎屑锆石LA-ICP-MS U-Pb测年方法,对鄂尔多斯盆地西缘北部贺兰山炭井沟、插旗沟和中部磁窑堡3个地区晚三叠世早期的物源进行分析。结果表明:研究区部分碎屑锆石阴极发光(CL)图像具有环带结构,大部分锆石Th/U值大于0.4,极少部分小于0.1,表明锆石来源以岩浆为主,变质为次。3个地区锆石年龄分布均有三组年龄峰值:古元古代早期—新太古代(2204.3~2610.1 Ma)、古元古代(1667~2171.8 Ma)和晚古生代(245.1~322.6 Ma),这3组年龄分别与新太古代末华北克拉通化的基本完成、古元古代晚期华北克拉通三大陆块(阴山陆块、鄂尔多斯陆块和东部陆块)之间的相互碰撞拼合以及晚古生代古亚洲洋向华北板块俯冲而形成的构造岩浆事件相对应。结合锆石年龄对比和岩相古地理分析得知,鄂尔多斯盆地西北缘晚三叠世早期物源来自北部和西北部地区,主要为古元古代孔兹岩带和阿拉善地块的变质岩和岩浆岩,其次为华北板块西部基底的岩浆岩和阿拉善地块海西期的岩浆岩。Laser ablation inductively coupled plasma-mass spectrometry(LA-ICP-MS)U-Pb was used on detrital zircons to analyze the provenance of the early Upper Triassic in the Tanjinggou,Chaqigou and Ciyaobao areas of the Helan Mountain in the northwestern Ordos Basin.It was found that Cathodoluminescence(CL)images of some zircons from the study area have annular structure.The Th/U ratio of most of the zircons was above 0.4,with very few below 0.1;these indicated that most of the zircons were from magma,with a small number from metamorphic rock.Three age peaks were evident in the age distributions of the zircons,one in each region:late Neoarchean-early Paleoproterozoic(2204.3-2610.1 Ma,corresponding to the completion of North China cratonization);Paleoproterozoic(1667-2171.8 Ma,corresponding to collision and assemblage of the Yinshan,Ordos and Eastern Continental Blocks);and late Paleozoic(245.1-322.6 Ma,corresponding to tectonomagmatic events related to subduction of the Paleo-Asian Ocean beneath the North China Plate).Comparison of zircon ages and palaeogeographic lithofacies analysis showed that early Upper Triassic provenances in the northwestern Ordos Basin were from the northern and northwestern regions,and were mainly derived from magmatic and metamorphic rocks of the Paleoproterozoic Alashan Block and Khondalite Belt.Secondary sources were the western basement of the North China Plate and the Hercynian magmatic rocks of the Alashan Block.

关 键 词：晚三叠世 碎屑锆石U-Pb定年 沉积物源 孔兹岩带 阿拉善地块 

分 类 号：P534.51[天文地球—古生物学与地层学] P597.3[天文地球—地质学]