西藏荣那超大型Cu-(Au)矿床黑云母矿物学特征及其对成矿的指示  

Mineralogical Features of Biotite from the Giant Rongna Cu-(Au)Deposit in Tibet and Their Implications for Mineralization

作　　者：刘通 张夏楠[2] 李光明 秦克章[3] 李金祥[4] 潘家永 余可龙[5] 赵俊兴 罗辉[1,2] LIU Tong;ZHANG Xianan;LI Guangming;QIN Kezhang;LI Jinxiang;PAN Jiayong;YU Kelong;ZHAO Junxing;LUO Hui(College of Earth Sciences,East China University of Technology,330013,Nanchang,PRC;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,330013,Nanchang,PRC;Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,100029,Beijing,PRC;State Key Laboratory of Tibetan Plateau Earth System,Environment and Resources(TPESER),Institute of Tibetan Plateau Research,Chinese Academy of Sciences,100101,Beijing,PRC;Zijin Mining Group Company Limited,361000,Xiamen,Fujian,PRC)

机构地区：[1]东华理工大学地球科学学院,南昌330013 [2]核资源与环境国家重点实验室,东华理工大学,南昌330013 [3]中国科学院矿产资源研究重点实验室,中国科学院地质与地球物理研究所,北京100029 [4]青藏高原地球系统与资源环境全国重点实验室,中国科学院青藏高原研究所,北京100101 [5]紫金矿业集团股份有限公司,福建厦门361000

出　　处：《江西科学》2025年第2期262-270,共9页Jiangxi Science

基　　金：国家自然科学基金项目(42102096,42462016);科技部第二次青藏高原科学考察研究项目(2019QZKK0806);江西省自然科学基金项目(20242BAB27002)。

摘　　要：荣那Cu-(Au)矿床位于西藏班公湖-怒江成矿带西段,是斑岩-高硫型浅成低温热液套合矿床,其成矿岩体为花岗闪长斑岩。根据黑云母的产状及成因,将荣那矿床中的黑云母分为3类:斑岩中浸染状黑云母(BtⅠ)、斑岩中斑晶黑云母(BtⅡ)和交代角闪石的新生黑云母(BtⅢ)。这些黑云母都比较富Mg,X_(Mg)=0.71~0.86,X_(Mg)=Mg/(Mg+Fe),其中Fe、Mg使用其摩尔分数计算。与岩浆成因的BtⅠ和BtⅡ相比,热液成因的BtⅢ的X_(Mg)值、Al_(2)O_(3)、SiO_(2)、F的含量更高,TiO_(2)、FeO、Cl的含量更低。BtⅢ的log(f(HF)/f(HCl))值小于BtⅠ和BtⅡ,即从岩浆到热液阶段f(HF)/f(HCl)值降低,可能是由于在熔流体分异过程中,Cl倾向于进入流体、F倾向于残留在熔体导致的。3类黑云母氧逸度均位于Ni-NiO(NNO)和Fe_(2)O_(3)-Fe_(3)O_(4)(HM)缓冲剂之间,表明荣那矿床的岩浆-热液体系具有较高的氧逸度。和岩浆成因的BtⅠ、BtⅡ相比,热液成因的BtⅢ氧逸度相对较低,这可能与磁铁矿的沉淀有关。The Rongna Cu-(Au)deposit is located in the western segment of the Bangong Lake-Nujiang metallogenic belt in Tibet.It is a telescoped porphyry high-sulfidation epithermal deposit,and its ore-forming rock is granodiorite porphyry.Based on the occurrence and genesis of biotite,the biotite in the Rongna deposit was divided into three types:disseminated biotite in porphyry(BtⅠ),phenocryst biotite in porphyry(BtⅡ)and newly-born biotite(replacing hornblende)(BtⅢ).The biotites from the Rongna deposit are relatively rich in Mg,with X_(Mg)values ranging from 0.71 to 0.86,X_(Mg)=Mg/(Mg+Fe),in which Fe and Mg are calculated using the mole fractions.Compared with magmatic BtⅠand BtⅡ,the contents of X_(Mg),Al_(2)O_(3),SiO_(2)and F in hydrothermal BtⅢare higher,while the contents of TiO_(2),FeO and Cl are lower.The log(f(HF)/f(HCl))values of BtⅠⅡare lower than those of BtⅠand BtⅡ,suggesting a decrease in f(HF)/f(HCl)from the magmatic to hydrothermal stage.This could arise from the different partition behavior of F and Cl during the exsolution of fluid from melt(Cl tends to enter fluid and F tends to remain in melt during the separation of melt and fluid).The oxygen fugacity of the three types of biotite is located between Ni-NiO(NNO)and Fe_(2)O_(3)-Fe_(3)O_(4)(HM)buffers,indicating that the magmatic-hydrothermal system of the Rongna deposit had relatively high oxygen fugacity.However,compared with magmatic BtⅠand BtⅡ,the oxygen fugacity of hydrothermal BtⅢis relatively lower,which may be related to the precipitation of magnetite.

关 键 词：Cu-(Au)矿床 黑云母 荣那 西藏 斑岩-浅成低温热液矿床 

分 类 号：P595[天文地球—地球化学]