巴颜喀拉山群中酸性侵入岩脉锆石U-Pb年龄及其意义  

U-Pb dating of zircons for intermediate-acidic dikes in Bayan Har Group and their geological significance

作　　者：王玺 陈泳霖 白国典 张铁林 王艳慧 WANG Xi;CHEN Yonglin;BAI Guodian;ZHANG Tielin;WANG Yanhui(Henan Academy of Geology,Zhengzhou 450001,Henan,China;Key Laboratory of Ore Forming Processes and Resources Utilization of Metal Minerals in Henan Province,Zhengzhou 450001,Henan,China)

机构地区：[1]河南省地质研究院,河南郑州450001 [2]河南省金属矿产成矿地质过程与资源利用重点实验室,河南郑州450001

出　　处：《矿产勘查》2023年第6期839-848,共10页Mineral Exploration

基　　金：中国地质调查局地质调查项目“青海省曲麻莱县卡巴纽尔多地区I46E003021、I46E004021、I46E005021幅1∶5万区域地质矿产调查”(12120113033018)资助。

摘　　要：巴颜喀拉山群是巴颜喀拉地块出露的主要地层单元,也是金、锑矿床的重要赋存层位和成矿物质来源。目前对出露于北巴颜喀拉山一带的砂岩与板岩组合,在沉积时代和归属上存在早—中三叠世与晚三叠世晚期两种不同认识。研究发现这套地层中发育较多中酸性岩脉,采用激光烧蚀多接收器电感耦合等离子体质谱仪(LA-ICP-MS)方法对具明显侵入特征的花岗闪长斑岩及二长斑岩岩脉进行了锆石U-Pb同位素年龄测定,前者加权平均年龄为(230.0±1.3)Ma,后者加权平均年龄为(207.1±1.6)Ma,认为该地区巴颜喀拉山群的沉积时代应不晚于中三叠世,而非前人认为的晚三叠世晚期。研究成果为这套地层形成于早—中三叠世进而归并为巴颜喀拉山群下亚群提供了有力证据,也为在该层位开展金、锑矿成矿规律研究等提供了有力支撑。The Bayan Har Group is the main stratigraphic unit exposed in the Bayanhar Terrain,and also an important hosting unit or source of the metallogenetic materials for the gold and antimony deposits.Two recogni-tions on depositional age and lithostratigraphic attribution of the association of sandstones and slates exposed in the North Bayan Har Mountain have been proposed as Early-Middle Triassic or Late Triassic.In this study,we found a series of intermediate-acid dykes intruding to the clastic sequence.Zircon U-Pb dating by LA-ICP-MS has been carried on a granodiorite porphyry and a monzonite porphyry of which field occurrences are both typical of intru-sions.The weighted mean 206Pb/238U ages of the granodiorite porphyry and monzonite porphyry samples are(230.0±1.3)Ma and(207.1±1.6)Ma,respectively.Consequently,the depositional age of the Bayan Har Group in the study area should be confined to earlier than~230 Ma,rather than the ending Late Triassic(Rhaetian Stage).We attribute the sandstone-slate association in the study area to Lower to Middle Triassic and thereby correlate it with the lower Bayan Har Group,which would further support the metallogenetic researches on gold and antimony deposits in this depositional sequence.

关 键 词：巴颜喀拉山群 中酸性侵入岩脉 锆石U-PB年龄 早—中三叠世 

分 类 号：P535[天文地球—古生物学与地层学]