广西花山岩体矿物学、年代学、地球化学特征及其大地构造意义
投稿时间:2017-11-11  修订日期:2018-03-18  点此下载全文
引用本文:蔡永丰.广西花山岩体矿物学、年代学、地球化学特征及其大地构造意义[J].地质与勘探,2018,54(5):940-956
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蔡永丰 桂林理工大学广西有色金属隐伏矿床勘查及材料开发协同创新中心&广西隐伏金属矿产勘查重点实验室广西桂林 zhouyun@glut.edu.cn 
基金项目:国家自然科学基金项目(编号 41502180和41503021)、广西高等学校科学研究项目(编号 KY2015ZD052)、同位素地球化学国家重点实验室(中国科学院广州地球化学研究所)(编号 SKLabIG-KF-16-06)和广西自然科学基金项目(编号 2015GXNSFBA139204和2017GXNSFAA198209)联合资助
中文摘要:中生代时期华南地区发育强烈的几乎同时期的花岗质岩浆作用和成矿作用,为阐明两者的联系,本文以桂东北花山岩体为研究对象,对其进行了详细的矿物化学成分、锆石U-Pb年代学和地球化学分析,并探讨了其成岩成矿作用。分析结果表明,花山岩体黑云母的含铁指数为0.68~0.80,属于铁叶云母,具有低的氧逸度;长石的端员组分主要为Ab,Or和An组分含量较低,斜长石主要为奥长石。年代学测试结果表明花山岩体形成于162 ± 1 Ma,为中侏罗纪晚期,与区域上钨锡成矿时代一致。花山岩体具有高硅富碱、贫CaO、MgO、Sr、Ba等特征,其FeOT/MgO和Ga/Al比值较高,同时富含Sn、Rb、Y、Zr、Nb和REE(除Eu外),表现出与A型花岗岩相似的地球化学特征。综合上述数据资料并结合区域地质资料,表明花山地区花岗岩的侵位时代分为燕山早期和燕山晚期两期次,而不是前人认为的形成于三个期次,其形成可能与岩石圈的拉张减薄有关;本区花岗岩低氧逸度、较高含铁指数及成岩温度等特征均有利于W-Sn矿床的形成,是本区钨锡矿床勘探的重点区域。
中文关键词:花岗岩 矿物化学 锆石U-Pb年代学 钨锡成矿作用 广西花山
 
Characteristics of mineralogy, geochronology and geochemistry of the granite in Huashan, Guangxi Province and its tectonic implication
Abstract:Mesozoic granitic magmatism and mineralization are common in South China. This work focused on the mineral composition, zircon U-Pb geochronology and geochemistry of the Huashan granite pluton intruded south of the Shiwandashan-Hangzhou belt. The purpose was to explore their relationship with the economically important Huashan tungsten–tin deposit in northeastern Guangxi Province, South China. Electron microprobe analyzer (EMPA) analysis indicates that biotite from the Huashan granite has high FeOT and low MgO contents with Fe/(Fe+Mg) values of 0.68 to 0.80, resembling to those of siderophyllite. The data of biotite thermometers show that they have low oxygen fugacities. Feldspar of the granite has high Ab and low Or and An contents similar to those of oligoclase. Geochronological analyses suggest that the pluton was intruded at 162 ± 1 Ma. Analysis results of geochemistry show that the Huashan granite pluton is characterized by high silicon and total alkali contents, and low CaO, MgO, Sr and Ba contents. The pluton has high FeOT/MgO and Ga/Al ratios and shows enrichment of Sn, Rb, Y, Zr, Nb and REE (except Eu). All these geochemical features are similar to A-type granite. Integrated with regional geological data, it is suggested that the Huashan granite formed in two periods, i.e., Early Yanshanian (~162 Ma) and Late Yanshanian (~148 Ma) rather than three stages proposed by previous studies. Both the Huashan granite and regional W–Sn deposits have the same formation age, suggesting that the ore-forming materials and fluids of these W–Sn deposits are closely related to the Early Yanshanian granitic magmatism, e.g., the Huashan granite pluton. Large-scale lithospheric extension and thinning should be responsible for the Mesozoic magmatism and mineralization in South China. Faults and folds cutting across the Huashan pluton including low oxygen fugacity and high Fe/(Fe+Mg) values of biotite might have provided favorable conditions for generating W-Sn deposits, which should be the key localities for W-Sn exploration.
keywords:granite, mineral composition, zircon U-Pb geochronology, W-Sn mineralization, Huashan
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