桂东北姑婆山岩体矿物学和年代学特征及其成岩成矿意义  

Mineral Compositional and Chronological Characteristics of Guposhan Pluton in Guangxi and Its Petrogenetic and Metallogenic Significance

作　　者：蔡永丰[1,2] 刘风雷 冯佐海 周云[1] 曾长育 Cai Yongfeng;Liu Fenglei;Feng Zuohai;Zhou Yun;Zeng Changyu(Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,Guilin University of Technology,Guilin 541004,Guangxi,China;Collaborative Innovation Center for Exploration of Hidden Nonferrous Metal Deposits and Development of New Materials in Guangxi,Guilin University of Technology,Guilin 541004,Guangxi,China;Guangxi Geological Survey Institute,Nanning530023,Chin)

机构地区：[1]桂林理工大学广西隐伏金属矿产勘查重点实验室,广西桂林541004 [2]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,广西桂林541004 [3]广西地质调查院,南宁530023

出　　处：《吉林大学学报（地球科学版）》2020年第3期842-856,共15页Journal of Jilin University：Earth Science Edition

基　　金：广西自然科学基金项目(2018GXNSFBA281069,2015GXNSFDA139029,2017GXNSFAA198209);广西高等学校科学研究项目(KY2015ZD052);广西八桂学者项目(2018,有色金属成矿理论与勘查技术)。

摘　　要：为揭示桂东北姑婆山一带花岗岩的成岩成矿特征,本文对姑婆山岩体进行了黑云母矿物化学成分分析和锆石U-Pb年代学研究。花岗岩中黑云母化学成分分析结果表明:黑云母具有富铁镁、贫钙钠的特征,w(TFeO)为26.78%~31.06%、w(MgO)为2.98%~6.60%,且w(TFeO)与w(MgO)呈明显的负相关性,说明其结晶过程中主要发生了Fe^2+←→Mg^2+的置换反应;黑云母的含铁指数为0.68~0.84,属于高铁黑云母,氧逸度为-17.0^-15.5,结晶温度为680~705℃,平均为695℃;黑云母的全铝压力计显示黑云母结晶的压力为69~179 MPa,平均为115 MPa,对应的侵位深度相当于2621~6755 m,平均深度为4331 m。年代学分析结果显示,采自姑婆山岩体的两个代表性花岗岩样品形成年龄分别为(162±3)和(163±2)Ma,为燕山早期,与华南中生代大规模岩浆-成矿作用时代一致。综合上述分析,姑婆山岩体形成于较高温度、低氧逸度、较浅的环境,显示出良好的锡成矿性,具有良好的找矿前景。In order to reveal the distribution of Early Yanshanian magmatism and its petrogenetic and metallogenic significance in South China,the authors studied the mineral composition and LA-ICP-MS zircon U-Pb geochronological characteristics of Guposhan pluton,which intruded in Huashan-Guposhan belt in northeast Guangxi.The geochronological analyses show two crystallized ages of(162±3)and(163±2)Ma,which are consistent with the time of Mesozoic large scale magmatism and mineralization in South China.The result of electron microprobe analyzer(EMPA)suggests that the biotite from Guposhan pluton has high TFeOand low MgO contents with Fe/(Fe+Mg)values of 0.68-0.84,resembling those of siderophyllite.The negative correlation between TFeOand MgO shows that the replacement between Fe^2+ and Mg^2+ occurred during crystallization of biotite.The data of biotite thermometers show high crystallization temperature of 680-705℃and low oxygen fugacity of-17.0--15.5.The results of Al-in-biotite barometer indicate the biotite crystallization pressure is 69-179 MPa,suggesting a crystallization depth of 2621-6755 m.Integrated with regional geological data,it could be inferred that the Early Yanshanian(~162 Ma)granitic magmatism is a common geological process,and a large scale of lithospheric extension and thinning might be the key mechanism to drive the Mesozoic magmatism and the corresponding mineralization in South China.Relatively high temperature,low oxygen fugacity,and shallow environment are favorable for Sn mineralization.

关 键 词：花岗岩 黑云母 锆石U-PB年代学 姑婆山岩体 桂东北 

分 类 号：P588.1[天文地球—岩石学] P597.3[天文地球—地质学]