吐拉盆地锆石U-Pb年代学:对成岩年龄、源区特征及阿尔金新生代走滑的制约  

Zircon U-Pb Age of Sandstones from Tula Basin and its Constrains on Sedimentary Ages,Provenances Characteristics,and Cenozoic Strike-slip along the Altyn Tagh Fault

作　　者：谢成龙[1] 孟栋材 王大华[2] 徐佑德[2] 王力[3] 常森 荆翰林 刘传泽 XIE Chenglong;MENG Dongcai;WANG Dahua;XU Youde;WANG Li;CHANG Sen;JING Hanlin;LIU Chuanze(School of Resources and Environmental Engineering,Hefei University of Technology,Hefei 230009,Anhui,China;Exploration and Development Research Institute,Shengli Oilfield Company of Petroleum,SINOPEC,Dongying 257200,Shandong,China;Geophysical Prospecting Research Institute,Jiangsu Oilfield Company of Petroleum,SINOPEC,Nanjing 210046,Jiangsu,China)

机构地区：[1]合肥工业大学资源与环境工程学院,安徽合肥230009 [2]中国石化胜利油田分公司勘探开发研究院,山东东营257200 [3]中国石化江苏油田分公司物探研究院,江苏南京210046

出　　处：《大地构造与成矿学》2020年第4期783-800,I0001-I0013,共31页Geotectonica et Metallogenia

基　　金：国家自然科学基金面上项目(41772210);国家自然科学基金重点项目(41830213);国家自然科学基金青年基金项目(41802220);国家级大学生创新实验项目(201810359053)联合资助。

摘　　要：吐拉盆地是青藏高原北缘的中、新生代陆相沉积盆地,其沉积物中的碎屑锆石年龄记录了重要的区域地质演化信息。本文以盆地西部吐拉牧场凹陷内原犬牙沟组砂岩为研究对象,应用LA-ICP-MS单颗粒锆石U-Pb定年法对7个样品中的650颗锆石进行了U-Pb同位素年代学分析,探讨了砂岩样品的成岩年龄、物源区特征、阿尔金断裂新生代大规模走滑等地质信息。分析结果显示,两个凝灰质砂岩样品中含有新生代岩浆锆石年龄信息,指示其沉积年龄应为66~51 Ma,因而地层应归属古近系,并非前人厘定的下白垩统犬牙沟组。砂岩中碎屑锆石年龄指示其沉积源区具有典型的劳亚大陆属性,并记录了罗迪尼亚大陆聚合与裂解、泛非造山、加里东造山及印支造山等全球关键构造事件年代学信息。物源分析显示其沉积物源应为南祁连及柴北缘块体,并非前人认为的阿尔金块体,其原始沉积位置相当于现今阿尔金断裂南缘冷湖以西一带。本次工作证实,吐拉盆地中生代时期原属柴达木盆地的一部分,在新生代阿尔金断裂大规模走滑作用下被拖拽分离至现今位置。区域构造分析表明,作为印度板块与欧亚板块碰撞的远程效应,阿尔金断裂左行走滑活动的开始时间应在51 Ma之后,滞后于板缘碰撞约4 Ma,两个阶段的总走滑位移量大于500 km。The Tula Basin is a Meso-Cenozoic continental deposit basin on the northern edge of the Tibetan Plateau,and the ages of detrital zircon from this basin bear important regional geological evolution information.To elucidate the sedimentary ages,provenances characteristics,and sinistral strike-slip along the Altyn Tagh Fault,LA-ICP-MS zircon U-Pb dating of 650 zircon grains selected from 7 sandstone samples from the Quanyagou Formation in the Tula Pastureland Sag,the westernmost unit of the Tula Basin was carried out.The Cenozoic ages ranging from 66 to 51 Ma acquired from two tuffaceous sandstone samples indicate that the strata belong to a Cenozoic unit rather than a Cretaceous one as was mentioned in previous literatures.The detrital zircon age spectra indicate that the provenances of these sandstones can be attributed to Laurasia,and may reveal globe critical tectonic events such as convergence and breakup of Rodinia,Pan-African orogeny,Caledonian orogeny,and Indosinian orogeny.Compared the zircon age spectra with those of the other blocks,we inferred that the provenances of the sediments were the North Qaidam and South Qilian blocks,but not the Altyn Tagh as was previously believed,and the initial sedimentary provenance was in the west of the present Lenghu area,along the south edge of the Altyn Tagh.It is confirmed that the Tula Basin was part of the Qaidam basin in Mesozoic,and was dragged from the Qaidam Basin to the present location due to sinistral strike-slip of the Altyn Tagh Fault in Cenozoic.As the remote effect of subduction of the Indian plate beneath the Eurasian plate,the onset of the sinistral strike-slip of the Altyn Tagh Fault was later than 51 Ma,and the displacement amount was far greater than 500 km.

关 键 词：吐拉盆地 物源分析 青藏高原 阿尔金断裂 左行走滑 

分 类 号：P542[天文地球—构造地质学] P597[天文地球—地质学]