班公湖-怒江缝合带同碰撞海沟盆地砂岩物源分析及其大地构造意义  

Provenance analysis of sandstone in the syncollisional trench basin of the Bangong Lake-Nujiang suture zone and its tectonic implications

作　　者：潘应娣 胡修棉[1] 马安林 梁文栋 PAN Yingdi;HU Xiumian;MA Anlin;LIANG Wendong(School of Earth Sciences and Engineering,Nanjing University,State Key Laboratory of Metallogenic Mechanism of Endogenous Metal Deposits,Nanjing,Jiangsu 210023,China;Institute of Sedimentary Geology,Chengdu University of Technology,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu,Sichuan 610059,China)

机构地区：[1]南京大学地球科学与工程学院,内生金属矿床成矿机制研究国家重点实验室,江苏南京210023 [2]成都理工大学沉积地质研究院,油气藏地质及开发工程国家重点实验室,四川成都610059

出　　处：《地质学报》2023年第9期2992-3005,共14页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41888101)资助的成果。

摘　　要：同碰撞海沟沉积可为重建板块缝合带大地构造演化、约束陆块初始碰撞时间提供重要信息。本文对班公湖-怒江缝合带西段的改则县亚多组和日土县多仁组进行了沉积学、岩相学、碎屑锆石年代学、重矿物研究。沉积学分析表明,多仁组、亚多组沉积于海底扇环境。最年轻的碎屑锆石年龄限制了最早沉积时代为晚侏罗世。多仁组、亚多组砂岩Q:F:L分别为52:4:44、32:8:60,均以丰富的沉积岩和酸性火成岩岩屑及少量的变质岩屑为特征;重矿物以磷灰石、锆石、电气石等稳定重矿物为主。多仁组和亚多组具有相似的碎屑锆石年龄分布模式,主峰分布在350~200 Ma、550~450 Ma、900~750 Ma、1900~1800 Ma、2550~2450 Ma范围内。这些数据表明,亚多组、多仁组碎屑物质来源于沉积区北侧的班公湖-怒江缝合带增生杂岩及南羌塘岩浆岩。多仁组、亚多组出现的大量沉积岩岩屑,表明物源区经历了广泛的构造缩短作用,导致沉积岩和同期岩浆岩被剥蚀,因此多仁组、亚多组是拉萨-羌塘同碰撞的产物。据此推断,沿班公湖-怒江缝合带改则-日土区域拉萨-羌塘初始碰撞发生在晚侏罗世多仁组、亚多组沉积之前。Syncollisional trench deposits can provide important information for reconstructing the tectonic evolution of the suture zone and constraining the time of initial collision of land masses.In this paper,sedimentological,petrographic,detrital zircon geochronological,and heavy mineral studies were carried out on the Yaduo Formation of Gaize area and the Duoren Formation of Ritu area in the western Bangong Lake-Nujiang suture zone.Sedimentological analysis shows that the Duoren and Yaduo formations were deposited in a submarine fan environment.The youngest detrital zircon age of the Duoren Formation constrains the depositional age to the Late Jurassic.The sandstone of the Duoren and Yaduo formations have Q:F:L ratio of 52:4:44 and 32:8:60,respectively,and are characterized by abundant sedimentary and acidic volcanic rock fragments.The heavy minerals of the sandstones of the Duoren and Yaduo formations are dominated by stable heavy minerals such as apatite,zircon and tourmaline.Both these formations have similar detrital zircon age distribution patterns,with the main peaks mainly distributed in the ranges of 350~200 Ma,550~450 Ma,900~750 Ma,1900~1800 Ma,and 2550~2450 Ma.These data suggest that the detritus of the Yaduo and Duoren formations originated from the accretionary complex in the Bangong Lake-Nujiang suture zone and the magmatic rocks in South Qiangtang north of the depositional area.The large amount of sedimentary detritus occurring in the Duoren and Yaduo formations indicates that the source area experienced extensive structural deformation,leading to the denudation of sedimentary rocks and contemporaneous magmatic rocks,and which is considered as a product of the Lhasa-Qiangtang syncollision.On this basis,the timing of initial Lhasa-Qiangtang collision occurred prior to the deposition of the Duoren and Yaudo formations(Late Jurassic).

关 键 词：晚侏罗世 多仁组 亚多组 物源分析 拉萨-羌塘碰撞 

分 类 号：P548[天文地球—构造地质学] P588.212.3[天文地球—地质学]