漠河盆地西部二十二站组碎屑锆石U-Pb年龄、地球化学特征及其物源意义  

Detrital zircon U-Pb dating and geochemical characteristics of the Ershi’erzhan Formation in western Mohe basin and its provenance significance

作　　者：段明新 周传芳 杨华本 蔡艳龙 魏小勇 徐建鑫 赵佳琪 DUAN Mingxin;ZHOU Chuanfang;YANG Huaben;CAI Yanlong;WEI Xiaoyong;XU Jianxin;ZHAO Jiaqi(School of Earth Sciences and Resources,China University of Geosc iences(Beijing),Beijing 100083,China;Harbin Center for Integrated Natural Resources Survey,China Geological Surey,Harbin,Heilongjiang 150081,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国地质调查局哈尔滨自然资源综合调查中心,黑龙江哈尔滨150081

出　　处：《地质学报》2021年第11期3317-3334,共18页Acta Geologica Sinica

基　　金：中国地质调查局项目(编号DD2016007803、DD20191014、DD20208004和DD20211589)联合资助的成果。

摘　　要：大兴安岭北部漠河盆地内广泛发育二十二站组,其形成时代及物质来源一直以来备受争议。本文在野外地质调查及岩相学的基础上,利用碎屑锆石LA-ICP-MS U-Pb法测年,并结合岩石地球化学等方法,探讨了二十二站组形成时代、物源区大地构造环境及沉积物来源。测年结果显示132个测点年龄主要分布在4个群落,分别为508.3~492.3 Ma;486.9~435.5 Ma;278.3~254.2Ma;209.5~178.1 Ma。本次获得二十二站组最小碎屑锆石年龄为178.1 Ma,并结合漠河盆地东西部碎屑锆石的年龄,综合认为二十二站组形成时代应为中晚侏罗世。地球化学分析结果显示,二十二站组砂岩的稀土元素与活动大陆边缘的稀土元素曲线吻合较好,且相对亏损高场强元素(Nb和Ta)和大离子亲石元素(Ba和Sr),相对富集高场强元素(La、Th、Zr、Hf),地球化学特征与活动大陆边缘相似。综合古流向、源区母岩分析、碎屑锆石测年分析、微量元素特征等诸多因素,本次研究认为本区二十二站组砂岩的母岩主要来源于盆地南缘广泛分布的前中生代沉积-变质基底(兴华渡口岩群、佳疙瘩组、额尔古纳河组等)及各期中酸性火成岩。To address the controversy regarding the formation age of the Ershi’erzhan Formation sandstone,in the Mohe basin of the northern Da Hinggan Mountains,this study presents results of LA-ICP-MS detrital zircon U-Pb dating in this paper,and discusses its provenance and tectonic setting together with the geochemistry of major and trace elements.The zircon U-Pb dating results show that 132 data are distributed in the following four periods,508.3~492.3 Ma,486.9~435.5 Ma,278.3~254.2 Ma,and 209.5~178.1 Ma.It is considered that the age of the Ershi’erzhan Formation should be Middle-Late Jurassic combined with the minimum age(178.1 Ma)of the zircon and the age of zircon in the east and west of Mohe basin.The geochemical analysis results show that the REE curves of the Ershi’erzhan Formation sandstone are in good agreement with the REE curves of the active continental margin,and are relatively depleted in high field strength elements(Nb and Ta)and large ion lithophile elements(Ba and Sr),and are relatively enriched in high field strength elements(La,Th,Zr and Hf).Based on the analysis of paleocurrent,source rock,zircon dating and trace element characteristics,it is believed that the parent rocks of the Ershi’erzhan Formation sandstone are mainly from the pre-Mesozoic sedimentary metamorphic basement(Xinghuadukou Group,Jiageda Formation,Erguna River Formation,etc.)and the intermediate acid igneous rocks.

关 键 词：漠河盆地 二十二站组 形成时代 构造环境判别 物源 

分 类 号：P597.3[天文地球—地球化学]