辽东前寒武纪沉积变质型铁矿床中伴生铀矿的成矿时代与测年结果可靠性分析  

The Ore-forming Age of the Uranium Mineralization Associated with Precambrian Sedimentary-Metamorphic Iron Deposits in Eastern Liaoning Province and Reliability Analysis of Dating Results

作　　者：孙欣宇 李立兴[2] 李厚民[2] 章永梅[1] 孟洁 李小赛[2] 王亿 SUN Xinyu;LI Lixing;LI Houmin;ZHANG Yongmei;MENG Jie;LI Xiaosai;WANG Yi(School of Earth Science and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Key Laboratory of Metallogeny and Mineral Assessment,Ministry of Natural Resources,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;Development and Research Center,China Geological Survey,Beijing 100037,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]自然资源部成矿作用与资源评价重点实验室,中国地质科学院矿产资源研究所,北京100037 [3]中国地质调查局发展研究中心,北京100037

出　　处：《岩矿测试》2023年第6期1090-1103,共14页Rock and Mineral Analysis

基　　金：国家重点研发计划项目(2022YFC2905400,2022YFC2903701);国家自然科学基金项目(42072112)。

摘　　要：辽东地区是中国成矿时代最古老的铀矿矿集区,有单铀型和铁矿伴生型两种,其中单铀型矿床成矿年龄已基本厘定,而铁矿伴生型铀矿成矿年龄尚不明确,制约了该类矿床的成因认识。晶质铀矿是铁矿伴生型铀矿中最主要的含铀矿石矿物,对其开展测年能够直接厘定铀矿成矿时代。本文对翁泉沟富蛇纹石磁铁矿矿石和弓长岭石榴子石蚀变岩中的晶质铀矿进行电子探针(EPMA)测年,并利用激光剥蚀电感耦合等离子体质谱法(LA-ICP-MS)对翁泉沟富蛇纹石磁铁矿矿石中的晶质铀矿进行U-Pb测年,两种测年结果相互验证,获得辽东地区铁矿伴生型铀矿的成矿时代为~1.85Ga,并在~1.78Ga遭受了后期热液事件的改造,与单铀型矿床成矿年龄一致,说明辽东地区单铀型和铁矿伴生型铀矿都形成于碰撞后伸展环境。辽东地区铁矿伴生型铀矿不同矿床的成矿热液在流体成分和温度上有差别,但都具有碱性和氧化的特征。BACKGROUND:The eastern Liaoning Province represents the eldest hydrothermal uranium ore cluster area in China.Two ore types are classified,including independent uranium mineralization and uranium mineralization associated with Precambrian sedimentary-metamorphic iron deposits.The ore-forming age of the former type has been well constrained at~1.85Ga,whereas the age of the latter type remains uncertain.Iron deposit-associated uranium mineralization developed in the Wengquangou B-Mg-Fe deposit,the Gaojiagou Fe deposit,and the Gongchangling Fe deposit.Geochronological studies on uraninite of the Wengquangou deposit yielded variable ages ranging from 2.0 to 1.8Ga[11-14],with some ages even older than the depositional ages of the hosting Liaohe Group(2.05 to 1.93Ga[15]).This inconsistency suggests that some uraninite grains used for dating are detrital in origin.The lack of reliable age constraints on the iron deposit-associated uranium mineralization has raised questions about its origin.It remains unknown whether the iron deposit-associated uranium mineralization resulted from the same hydrothermal process and formed at the same tectonic setting when compared with the independent uranium mineralization.OBJECTIVES:To determine the metallogenic age and verify the accuracy of the age in uranium.METHODS:The instrument JXA-iHP200F was used for analysis,and the age was calculated according to Ranchin’s empirical formula[38].The analytical conditions were 20kV acceleration voltage,50nA beam current,and 5μm beam spot size.A further LA-ICP-MS U-Pb dating method was used to verify the EPMA chemical ages of the uraninite,using a 193nm GeoLasPro and Agilent 7900 ICP-MS with a laser spot size of 16μm.RESULTS:The calculated age of the Wengquangou deposit ranges from 1899 to 1324Ma,but it is mainly concentrated from 1899 to 1741Ma.Two peaks at 1859Ma and 1784Ma are constrained by an age frequency distribution histogram.This result is younger than the deposition age of the Liaohe Group.The age of the Gongchangling deposit range

关 键 词：晶质铀矿 U-Pb定年 电子探针 电感耦合等离子体质谱法 铁矿伴生型铀矿 成矿时代可靠性分析 

分 类 号：O785.5[理学—晶体学] P612[天文地球—矿床学] P597.3[天文地球—地质学]