柴北缘赛坝沟金矿床花岗斑岩脉的成因及动力学背景:来自年代学和地球化学的证据  

Petrogenesis and Geodynamic Setting of Granite Porphyry Dike in Saibagou Gold Deposit,Northern Margin of Qaidam:Evidence from Geochronology and Geochemistry

作　　者：朱德全 唐名鹰 丁正江 朱海波 王炜晓 张宇 何宗围 吴洪彬 ZHU Dequan;TANG Mingying;DING Zhengjiang;ZHU Haibo;WANG Weixiao;ZHANG Yu;HE Zongwei;WU Hongbin(No.248 Geological Brigade of Shandong Nuclear Industry,Qingdao,Shandong 266000,China;School of Resources and Environmental Engineering,Shandong University of Technology,Zibo,Shandong 255000,China;No.8 Institute of Geology and Mineral Resources Exploration of Shandong Province,Rizhao,Shandong 276800,China;Key Laboratory of Nonferrous Metal Prospecting and Resource Evaluation in Shandong Provincial Bureau of Geology and Mineral Resources,Rizhao,Shandong 276800,China;No.6 Exploration Institute of Geology and Mineral Resources Exploration of Shandong Province,Weihai,Shandong 264209,China;Engineering Laboratory of Deep Gold Exploration Big Data Application and Development of Shandong Province,Weihai,Shandong 264209,China;Henan Institute of Geosciences,Zhengzhou,Henan 450001,China)

机构地区：[1]山东省核工业二四八地质大队,山东青岛266000 [2]山东理工大学资源与环境工程学院,山东淄博255000 [3]山东省第八地质矿产勘查院,山东日照276800 [4]山东省地矿局有色金属矿找矿与资源评价重点实验室,山东日照276800 [5]山东省第六地质矿产勘查院,山东威海264209 [6]山东省深部金矿探测大数据应用开发工程实验室,山东威海264209 [7]河南省地质调查院,河南郑州450001

出　　处：《现代地质》2022年第3期898-910,共13页Geoscience

基　　金：国家自然科学基金项目(41973048);山东省地矿局科技创新项目(Y201924)。

摘　　要：青海乌兰县赛坝沟金矿床位于柴北缘结合带东部,为一中型石英脉型金矿。为进一步确定该矿床形成年龄和成因,对矿区内与成矿关系密切的花岗斑岩脉进行锆石U-Pb年代学和岩石地球化学研究。花岗斑岩LA-ICP-MS锆石U-Pb年龄为(372.4±4.1)Ma,是晚泥盆世岩浆活动的产物。花岗斑岩具高硅、富碱的特征,分异指数(DI)为81.40~84.54,固结指数(SI)为3.56~8.17,表明岩石结晶分异程度较高;微量元素原始地幔标准化图解显示La、Hf、Rb、Th相对富集,而Nb、Ta、P、Ti、Ba、Sr相对亏损;稀土元素球粒陨石标准化配分曲线呈右倾的轻稀土元素富集型,且具轻微Eu元素负异常。综合判别图解分析,认为花岗斑岩属过铝质钙碱性的I型花岗岩。赛坝沟金矿床花岗斑岩形成时间与柴北缘中晚泥盆世陆内伸展时间一致,整体形成于柴北缘中晚泥盆世陆内伸展阶段的后造山构造环境中。脉岩紧邻矿体产出并充填在构造裂隙中,其形成与成矿年龄相接近,因此可将赛坝沟金矿形成时间上限限定在372.4 Ma。后期找矿勘查工作应重点围绕花岗斑岩脉展开。The medium-sized Saibagou quartz vein-type gold deposit is located in the eastern part of the northern margin of Qaidam.The granite porphyry zircon U-Pb geochronology and geochemistry were analyzed in this study.The LA-ICP-MS zircon U-Pb dating yielded(372.4±4.1)Ma,indicating Late Devonian magmatism.The granite porphyry is characterized by high SiO_(2) and alkali-rich,with differentiation index(DI)of 81.40-84.54 and solidification index(SI)of 3.56-8.17,indicating substantial fractionation.The geochemical features show remarkable enrichments in La,Hf,Rb,and Th,but depletions in Nb,Ta,P,Ti,Ba,and Sr.The total rare-earth element(ΣREE)is 71.80×10^(-6)-75.21×10^(-6),and the REE patterns are right-inclining with slightly negative Eu anomalies(δEu=0.77-0.96).Discriminant diagram shows that the granite porphyry is peraluminous calc-alkaline I-type,and was likely formed in a post-orogenic setting during the Middle-Late Devonian intracontinental extension in the northern margin of Qaidam.The granitic magmatism was likely syn-ore and occurred close to the orebodies and filled in structures.Therefore,the maximum age of the Saibagou gold mineralization can be set at 372.4 Ma,and future prospecting work should focus on the granitic porphyry dikes.

关 键 词：花岗斑岩 年代学 地球化学 构造环境 赛坝沟金矿床 柴北缘 

分 类 号：P588.1[天文地球—岩石学] P597[天文地球—地质学] P618.51