山东莱芜张家洼铁矿床金云母^(40)Ar/^(39)Ar定年及其对成矿构造背景的启示  

Phlogopite;Ar/;Ar dating of the Zhangjiawa iron deposit,Laiwu district,Shandong Province:implications for regional iron skarn mineralization of North China Craton

作　　者：段壮 高明波 高继雷 李春稼 冯启伟 李思远 高稳胜 王宪镇 徐仲义 李建威 DUAN Zhuang;GAO Mingbo;GAO Jilei;LI Chunjia;FENG Qiwei;LI Siyuan;GAO Wensheng;WANG Xianzhen;XU Zhongyi;LI Jianwei(Institule of Geoph ysical and Geochemical Ex ploration,Chinese Academy of Geological Sciences,Langfang,Hebei 065000,China;Key Laboratory for Geochemical Ex ploration Technology,Ministry of Natural Resources,Lang.fang,Hebei 065000,China;No.1 Institue of Geology and Mineral Resources of Shandong Province,Jinan,Shandong 250100,China;Shandong Engineering Laboratory for High Grade Iron Ore Ex ploration and Exploitation,Jinan,Shandong 250100,China;School of Earth Resources,China University of Geosciences,Wuhan,Hubei 430074.China;State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan,Hubei 430074.China;Geological Ex ploration Institute of Shandong Zhengyuan,China Metallurgical Geology Bureau,Jinan,Shandong 250101.China;Institute of Hydrogeology and Engineering Geology Shandong Provincial Bureau of Geology&Mineral Resources,J inan,Shandong 250014,China)

机构地区：[1]中国地质科学院地球物理地球化学勘查研究所,河北廊坊065000 [2]自然资源部地球化学探测重点实验室,河北廊坊065000 [3]山东省第一地质矿产勘查院,山东济南250100 [4]山东省富铁矿勘查技术开发工程实验室,山东济南250100 [5]中国地质大学资源学院,湖北武汉430074 [6]中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉430074 [7]中国冶金地质总局山东正元地质勘查院,山东济南250101 [8]山东省地质矿产勘查开发局八○一水文地质工程地质大队,山东济南250014

出　　处：《地质学报》2022年第4期1279-1296,共18页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号42002105);山东省地矿局局控项目(编号KY201902);中国地质调查局地质调查项目(编号DD20190571);科技部“973”项目(编号2012CB416802)联合资助的成果。

摘　　要：华北地区是我国最大的矽卡岩型富铁矿床集中区,但目前对区域铁矿床的成矿年代学研究尚不系统和全面,从而制约了对其成矿构造背景的理解。山东莱芜张家洼矽卡岩型铁矿床是华北克拉通东部最重要平炉富铁矿产地之一,铁矿体主要赋存于早白垩世矿山岩体与中奥陶统碳酸盐岩的接触带、石炭系本溪组与奥陶系间不整合面的层间构造破碎带。金云母是张家洼铁矿床最主要的含水矽卡岩矿物,且与磁铁矿密切共生,对其进行^(40)Ar/^(39)Ar定年可为张家洼铁矿床的成矿时代提供约束。本文对张家洼铁矿床I号矿区和港里矿区的两件金云母单矿物样品进行了激光阶段加热^(40)Ar/^(39)Ar同位素分析,获得很好的坪年龄,分别为129.7±0.8Ma和131.5±1.2 Ma(2σ)。上述年龄数据与矿山岩体的锆石和矽卡岩中热液榍石的U-Pb年龄一致,证实张家洼铁矿床的成矿时代为130Ma左右。对张家洼及华北克拉通其他矽卡岩型铁矿床现有同位素年龄数据的综合分析表明,整个华北克拉通内的矽卡岩型铁矿成矿作用具有同时性和爆发性,绝多大数矿床均形成于130Ma左右,指示华北地区大规模矽卡岩型铁成矿作用是对华北克拉通岩石圈减薄和破坏的响应。The North China Craton(NCC) hosts numerous iron skarn deposits, which are the most important source of high-grade iron ores in China. However, the comprehensive and systematic study of ore-forming geochronology for iron mineralization of the NCC are scarce, which hampers the understanding of its tectonic setting. The Zhangjiawa iron skarn deposit in the Laiwu district of Shandong Province is the most important high-grade iron deposit in the eastern NCC. The iron orebodies are mainly located along the contact zones between the Kuangshan dioritic intrusion and Middle Ordovician carbonate rocks, and hosted in fractures overprinting the unconformity between the Carboniferous Benxi Formation and middle Ordovician strata. The retrograde skarn stage is the main hydrothermal iron mineralization stage of the Zhangjiawa deposit, showing magnetite is closely intergrown with hydrothermal phlogopite. In this study, the two phlogopite samples from the Zhangjiawa I and Gangli mining areas yielded^(40)Ar/^(39)Ar plateau ages of 129.7±0.8 Ma and 131.5±1.2 Ma(2σ), respectively. Using integrated information about mineral paragenesis and the U-Pb ages of magmatic zircon from the Kuangshan intrusion and hydrothermal titanite from skarns, we infer that the^(40)Ar/^(39)Ar system in phlogopite remain closed with ore deposition, indicating that the Zhangjiawa iron skarn deposit formed in the early stage of Early Cretaceous about 130 Ma. In combination with existing isotopic age data of other iron skarn deposits and related intrusions in North China Craton, we conclude that iron skarn mineralization throughout the North China took place at ca. 130 Ma, coupled with the culmination of lithospheric thinning and destruction of the North China Craton, and show a genetic link between the two.

关 键 词：金云母 ^(40)Ar/^(39)Ar定年 张家洼铁矿床 成矿构造背景 华北克拉通 

分 类 号：P618.31[天文地球—矿床学]