藏北革吉北部竟柱山组地球化学与碎屑锆石U-Pb年代学特征及构造意义  

Geochemical characteristics, detrital zircon U-Pb geochronology,and its tectonic significance for the Jingzhushan Formation from northern region of Geji County, northern Tibet

作　　者：李宝龙[1] 范海滨 朱德全 彭勃 郭平 周磊[5] 李宇飞 LI Baolong;FAN Haibin;ZHU Dequan;PENG Bo;GUO Ping;ZHOU Lei;LI Yufei(NLR Key Laboratory of Metallogeny and Mineral Resource Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing,100037;Shandong Provinical No.4 Institute of Geological and Mineral Survey,Weifang,Shandong,261021;Shandong Provinical No.8 Institute of Geological and Mineral Survey,Rizhao,Shandong,276826;School of Earth Sciences and Resources,China University of Geosciences,Beijing,100083;Geochemistry Exploration Brigade of Sichuan Bureau of Exploration and Development of Geology and Minerals Resources,Deyang,Sichuan,618000;Hebei Building Materials Industry Design and Research Institute,Shijiazhuang,050000)

机构地区：[1]中国地质科学院矿产资源研究所,自然资源部成矿作用与资源评价重点实验室,北京100037 [2]山东省第四地质矿产勘查院,山东潍坊261021 [3]山东省第八地质矿产勘查院,山东日照276826 [4]中国地质大学地球科学与资源学院,北京100083 [5]四川省地质矿产勘查开发局化探队,四川德阳618000 [6]河北省建筑材料工业设计研究院,石家庄050000

出　　处：《地质学报》2020年第12期3657-3673,共17页Acta Geologica Sinica

基　　金：国家自然科学青年基金(编号41802103);国家重点研发计划(编号2018YFC0604101);中国地质调查局地质调查项目(编号DD20190167)资助成果。

摘　　要：沿班公湖-怒江缝合带近东西向不连续分布的上白垩统竟柱山组(K2j),是洋-陆转换后的陆相沉积。因其东西向空间跨度较大,其准确的形成时限和砂岩源区的构造环境存在争议。本文采集西藏革吉县北部竟柱山组粗砂岩,对其碎屑锆石进行LA-ICP-MS U-Pb测年和主微量元素分析。样品碎屑锆石U-Pb谐和年龄值范围集中于100~130Ma和150~170Ma;在碎屑锆石年龄频谱图上,主要出现111.7Ma和160.1Ma两个峰值。最新的碎屑锆石年龄加权平均值为105.3Ma,表明竟柱山组应在早白垩世末期之后沉积。SiO2含量为52.92%~69.47%,Al2O3含量为5.22%~14.34%。高场强元素Ta、Nb、Ti亏损,Hf、Th及REE富集;大离子亲石元素Ba亏损,Rb、K富集。主微量元素特征及判别图解表明,研究区竟柱山组砂岩源区构造背景为大陆岛弧环境,物源为中酸性火成岩。The Upper Cretaceous Jingzhushan Formation(K2j), distributed discontinuously along the Bangong Co-Nujiang suture zone with an approximately E-W trend, is a continental deposit followingthe ocean-continent fully completed conversion.Due to its large east-west spatial span, its exact formation time and the tectonic environment of the sandstones’ source area are controversial.We have collected the coarse sandstone of the Jingzhushan Formation from northern region of Geji County, Tibet, and analyzed the characteristics of detrital zircon LA-ICP-MS U-Pb age, and the main and trace elements of the sandstone. The U-Pb concordia age of sandstones from the Jingzhushan Formation is concentrated at 100~130 Ma and 150~170 Ma. The zircon age shows two peaks of 111.7 Ma and 160.1 Ma on the detrital zircon age spectrum map of the Jingzhushan Formation sandstone. The latest detrital zircon weighted average age is 105.3 Ma, indicating that the Jingzhushan Formation should have been deposited after the early Cretaceous. The content of SiO2 was 52.92%~69.47%.The content of Al2O3 was 5.22%~14.34%.High field strength elements Ta, Nb and Ti are depleted, while there is enrichment of Hf, Th and REE. Large ion lithophile elements Ba are depleted, and there is enrichmentin Rb and K. The characteristics of the main and trace elements and the discriminant diagrams show that the tectonic background of the source area of sandstones from the Jingzhushan Formation in the study area should be continental island arc, and the original rock of the Jingzhushan Formation sandstones is intermediate-acid igneous rock.

关 键 词：班公湖-怒江缝合带 竟柱山组 锆石U-PB年代学 砂岩地球化学 构造背景 

分 类 号：P597.3[天文地球—地球化学] P548[天文地球—地质学]