广西大厂矿田笼箱盖花岗岩与锌铜矿床和锡多金属矿床成矿关系分析  

Longxianggai granitic magmatism and its relationship with Zn-Cu and Sn-polymetallic deposits in the Dachang ore field,Guangxi,China

作　　者：廖娟 黄文婷[1] 伍静 张健 欧阳柳芸 梁华英[1] LIAO Juan;HUANG Wenting;WU Jing;ZHANG Jian;OUYANG Liuyun;LIANG Huaying(Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;University of Chinese Academy of Sciences,Beijing 100049,China;College of Resources,Environment and Materials,Guangxi University,Nanning 530004,Guangxi,China;MOE Key Laboratory of Environment Change and Resources Use in Beibu Gulf,Nanning Normal University,Nanning 530001,Guangxi,China)

机构地区：[1]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广东广州510640 [2]中国科学院大学,北京100049 [3]广西大学资源环境与材料学院,广西南宁530004 [4]南宁师范大学北部湾环境演变与资源利用教育部重点实验室,广西南宁530001

出　　处：《地球化学》2024年第6期886-900,共15页Geochimica

基　　金：国家自然科学基金项目(42062007、41772065);广西高校中青年教师科研基础能力提升项目(2020KY09024)联合资助。

摘　　要：广西大厂矿田笼箱盖黑云母花岗岩内外接触带发育矽卡岩型Zn-Cu矿床,远离岩体发育大型–超大型Sn多金属矿床。目前多数观点认为Sn多金属矿床和Zn-Cu矿床都和笼箱盖岩体岩浆作用有关。本研究通过大厂矿田成岩成矿年龄,笼箱盖黑云母花岗岩的主量、微量元素组成以及黑云母的矿物化学成分,探讨岩浆氧逸度、Sn和Cu成矿潜力及Sn多金属矿床与Zn-Cu矿床成矿关系。笼箱盖黑云母花岗岩主量、微量元素组成特征及矿物组成表明,黑云母花岗岩为S型花岗岩;岩体黑云母在Fe^(3+)-Fe^(2+)-Mg^(2+)三角图上,位于FMQ与NNO之间,略高于Sn成矿岩浆,接近Cu成矿岩浆;岩体黑云母中Sn含量高,平均为185×10^(-6),而岩体Sn含量较低,平均为18.2×10^(-6),据体积及比重计算,岩体中90%以上Sn主要以Sn4+形式赋存于黑云母中,表明笼箱盖岩体岩浆氧逸度较高,岩浆作用有利于Cu成矿,而不利于Sn成矿。笼箱盖黑云母花岗岩呈富集轻稀土元素、亏损重稀土元素、弱Eu负异常特征,其Zr/Hf和Nb/Ta值分别为17.4~38.9和3.37~10.1,表明岩浆结晶分异程度低于典型成Sn花岗岩,也不利于Sn成矿。此外,笼箱盖花岗岩的锆石U-Pb年龄大于Sn多金属矿床的成矿年龄,而与拉么Zn-Cu矿床的成矿年龄接近,表明笼箱盖花岗岩可能与Sn成矿无关。以上地球化学特征和笼箱盖岩体Cu内Sn外反向分带等特征,表明Sn多金属矿床和矽卡岩型Zn-Cu矿床不属于同一岩浆–热液成矿体系,矽卡岩型Zn-Cu矿床与笼箱盖岩体岩浆作用有关,而Sn多金属矿床和笼箱盖岩体岩浆作用关系不大。The skarn Zn-Cu deposit occurs in the inner and outer contact zone of the Longxianggai biotite granite,while the large and super-large Sn-polymetallic deposits are located far away from the granite in the Dachang ore field,Guangxi.Many researchers have suggested that both the Sn-polymetallic deposits and Zn-Cu deposit are genetically related to the Longxianggai biotite granite.To unravel the magmatic oxygen fugacity,Sn and Cu mineralization potential,and the genetic relationships of Sn-polymetallic deposits and Zn-Cu deposit,a comprehensive investigation of whole-rock elemental composition and mineral geochemistry of Longxianggai biotite granite integrated with previously published ages of mineralization and magmatism was carried out.The whole-rock geochemical data and mineral composition of the Longxianggai biotite granite indicate that it is a S-type granite.In the biotite Fe^(3+)-Fe^(2+)-Mg^(2+)ternary diagram,the granite is located between the FMQ and NNO buffers,slightly higher than the Sn-related magma but close to the Cu-related magma.The Sn content of biotite(with an average of 185×10^(-6))is much higher than that of the biotite granite(with an average of 18.2×10^(-6)),indicated that more than 90% of Sn in biotite granite is Sn^(4+)within the biotite.These characteristics suggest that the magma of biotite granite is rather oxidized,which hinders Sn enrichment during late magmatic evolution but facilitates Cu enrichment and mineralization.The biotite granite was LREE-enriched and HREE-depleted,with weak negative Eu anomalies and Zr/Hf and Nb/Ta ratios of 17.4-38.9 and 3.37-10.1,respectively,indicating that the biotite granite was less differentiated than typical Sn-related granites,which is unfavorable for tin mineralization.In addition,the Longxianggai biotite granite has U-Pb age older than the Sn mineralization but similar to the Zn-Cu mineralization.Therefore,we suggest that the Sn-polymetallic deposits and Zn-Cu deposit are not genetically related to the same magmatic-hydrothermal system.Our results

关 键 词：大厂矿田 Sn多金属矿床 矽卡岩型Zn-Cu矿床 黑云母 氧逸度 

分 类 号：P611[天文地球—矿床学]