云南个旧锡铜矿集区石榴子石地球化学特征及成矿指示  

Metallogenic indication from geochemical characteristics of garnet in Gejiu Sn-Cu ore-concentrated area,Yunnan Province

作　　者：张银平 邵拥军[1,2] 熊伊曲 席振铢[1,2] 芦磊 张敏 毛禹杰 ZHANG YinPing;SHAO YongJun;XIONG YiQu;XI ZhenZhu;LU Lei;ZHANG Min;MAO YuJie(School of Geosciences and Info-Physics,Central South University,Changsha 410083,Hunan,China;Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitor(Central South University),Ministry of Education,Changsha 410083,Hunan,China;Yunnan Tin Company Limited,Gejiu 661000,Yunnan,China)

机构地区：[1]中南大学地球科学与信息物理学院,湖南长沙410083 [2]中南大学有色金属成矿预测与地质环境监测教育部重点实验室,湖南长沙410083 [3]云南锡业股份有限公司,云南个旧661000

出　　处：《矿床地质》2022年第4期682-701,共20页Mineral Deposits

基　　金：国家自然科学基金项目(编号:42172085);湖南省创新团队项目(编号:2021RC4055);云南锡业股份有限公司大屯锡矿研究项目、湖南省重点领域研发计划项目(编号:2019SK2261);湖南省自然资源厅科技项目(编号:2021-16);国土资源评价与利用湖南省重点实验室开放课题(编号:#SYS-ZX-202105);湖南省地质院科研项目(编号:HNGSTP202105)联合资助。

摘　　要：云南高松矿床中高峰山矿段和老厂矿床中竹叶山矿段分别是个旧超大型锡铜多金属矿集区发育的典型矽卡岩型锡、铜矿段。为查明个旧矿集区锡铜成矿环境的差异,文章选取上述2个矿段矽卡岩中的石榴子石为研究对象,根据产状和矿物共生关系将石榴子石分为与高峰山花岗岩有关早期(Grt-GS1)、晚期(Grt-GS2)、与竹叶山花岗岩有关(Grt-ZS)和与玄武岩有关(Grt-ZX)共4类。电子探针(EPMA)和激光剥蚀等离子质谱(LA-ICP-MS)分析表明:Grt-GS1(Adr_(10.58-20.27)Grs_(38.62-48.28)Spe_(21.06-32.37)Alm_(11.88-18.03))成分复杂且变化范围较大,而Grt-GS2(Adr_(48.09-69.73)Grs_(23.84-48.87)Spe_(3.29-9.58))和Grt-ZS(Adr_(13.97-16.06)Grs_(78.08-79.71)Spe_(2.15-2.60))成分简单且变化小;稀土元素配分曲线均呈HREE富集、LREE亏损的“左倾型”,并具明显的负Eu异常。Grt-ZX成分简单且较均一(Adr_(20.12-21.99)Grs_(70.84-71.44)Pyr_(6.29-7.92)),稀土元素配分曲线呈HREE亏损、LREE富集的“右倾型”,呈明显的正Eu异常,且F、Cl、U、Th、Pb、V、Cr、Co、Ni、Zn、Ti等元素含量均高于其余3类石榴子石。所有石榴子石REE^(3+)与Mg^(2+)的正相关性表明,REE^(3+)受[X^(2+)]Ⅷ-1[REE^(3+)]Ⅷ+1[Y^(3+)]Ⅳ-1[Y^(2+)]Ⅳ+1替换机制的控制,REE^(3+)主要替代Mg^(2+)进入石榴子石晶格。石榴子石的U、Sn含量及稀土元素配分特征指示:高峰山石榴子石(Grt-GS1和Grt-GS2)在演化过程中氧逸度明显升高、竹叶山石榴子石(Grt-ZS和Grt-ZX)形成的氧逸度总体高于高峰山,但Grt-ZX形成时氧逸度低于Grt-ZS。稀土元素特征显示:Grt-GS1、Grt-GS2与Grt-ZS均形成于弱酸性环境,而Grt-ZX形成于近中性且富F、Cl的环境下。∑REE^(3+)与Y呈良好的正相关性和REE含量变化指示4类石榴子石均形成于封闭或近封闭的体系中,在接近平衡和低水岩比的条件中受扩散交代作用缓慢生长而形成。综合研究表明,玄武岩对成矿的影响在于改变了�The Gaofengshan ore section in the Gaosong deposit and the Zhuyeshan ore section in the Laochang deposit are two typical skarn tin and copper ore sections developed in the Gejiu giant tin-copper polymetallic ore concentration district,respectively.In order to find out the differences between tin-and copper-forming environment in ore concentration area,garnet from the two ore sections were studied in detail.According to the occurrence and mineral assemblages,garnet can be divided into Gaofengshan granite-related early stage(Grt-GS1),late stage(Grt-GS2),Zhuyeshan granite-related stage(Grt-ZS)and basalt related stage(Grt-ZX).Electron probe and Laser Ablation-inductively Coupled Plasma-Mass Spectrometry(LA-ICP-MS)analytical results show that Grt-GS1(Adr_(10.58-20.27)Grs_(38.62-48.28)Spe_(21.06-32.37)Alm_(11.88-18.03))has a complex and variable composition,while Grt-GS2(Adr_(48.0969.73)Grs_(23.84-48.87)Spe_(3.29-9.58))and Grt-ZS(Adr_(13.97-16.06)Grs_(78.08-79.71)Spe_(2.15-2.60))have simple and relatively homogeneous composition,and both three types of garnet are HREE-enriched and LREE-depleted with obvious negative Eu anomalies.The composition of Grt-ZX is simple and homogeneous(Adr_(20.12-21.99)Grs_(70.84-71.44)Pyr_(6.29-7.92)),and the rare-earth element patterns are HREE-depleted and LREE-enriched with obvious positive Eu anomalies,as well as the contents of F,Cl,U,Th,Pb,V,Cr,Co,Ni,Zn and Ti are higher than other three types of garnets.The positive correlation between REE^(3+)and Mg^(2+)in all garnet indicates that REE^(3+)is controlled by the[X^(2+)]Ⅷ-1[REE^(3+)]Ⅷ+1[Y^(3+)]Ⅳ-1[Y^(2+)]Ⅳ+1 substitution mechanism,and REE^(3+)mainly replaces Mg^(2+)into the garnet lattice.The U and Sn contents of garnet and the REE patterns indicate that the oxygen fugacity was significantly increased du-ring the evolution of Gaofengshan garnet(Grt-GS1 and Grt-GS2),and the oxygen fugacity of Zhuyeshan garnet(Grt-ZS and Grt-ZX)are generally higher than those of Gaofengshan garnet,while the oxygen fugacity of Grt-ZX was lower tha

关 键 词：地球化学 石榴子石 成矿指示 锡矿床 个旧 

分 类 号：P618.41[天文地球—矿床学] P618.44[天文地球—地质学]