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引用本文:杜玉龙,方维萱,鲁佳. 玻利维亚TUPIZA铜矿床碱性火山岩的岩相地球化学特征及找矿预测[J]. 中国地质, 2020, 47(2): 315-333.
DU Yulong,FANG Weixuan,LU Jia. Lithofacies geochemistry characteristics of alkali volcanic rocks and prospecting prediction in Tupiza copper deposit, Bolivia[J]. Geology in China, 2020, 47(2): 315-333(in Chinese with English abstract).
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玻利维亚TUPIZA铜矿床碱性火山岩的岩相地球化学特征及找矿预测
杜玉龙1,2, 方维萱3, 鲁佳1
1.昆明理工大学国土资源工程学院, 云南 昆明 650093;2.中色地科矿产勘查股份有限公司, 北京 100012;3.有色金属矿产地质调查中心, 北京 100012
摘要:
在沉积型铜矿床中,蚀变火山岩具有特殊的成岩成矿意义。采用构造岩相学填图、火山岩岩相类型划分和电子探针分析等综合方法,对玻利维亚Tupiza铜矿进行研究,结果表明在玻利维亚Tupiza铜矿区内,发育中深成相、次火山侵入相(次火山颈相)、火山溢流相、火山碎屑流相、沉火山岩相等。岩石组合类型为辉绿岩-辉绿玢岩、辉长岩-辉长玢岩、碱性玄武岩、钾质粗面玄武岩、橄榄玄武粗面安山岩和安粗岩。在区域上,碱性玄武质岩浆侵位具多期多阶段性,在Tupiza铜矿区内,采用矿物温度-压力计估算,镁普通角闪石形成温度630.97~748.43℃,压力55~251 MPa,推测成岩深度为2.04~9.27 km,揭示经历多阶段减压增温(减压熔融)、减压降温的成岩演化过程,在岩浆减压侵位过程中具有高温高氧化成岩环境。绿泥石形成温度为112~305℃,lgf(O2)为-45.03~-56.68,lgf(S2)为-4.46~-18.07,属中—低温还原成岩成矿环境,代表铜(银)主成矿期。次火山热液蚀变成岩成矿作用形成了Tupiza铜(银)矿床,蚀变火山岩是铜矿床的成矿物质供给系统,铜(银)矿体富集于蚀变火山岩相体与构造叠加部位,在NNE与NW向构造交汇部位尤为富集。在上白垩统阿诺依菲雅组第三岩性段蚀变火山岩层之下的第二岩性段顶部黄铁矿化砂砾岩中,验证钻孔揭露了铜(钴)矿化体,是深部寻找隐伏沉积岩型铜(钴)矿体找矿标志。在蚀变火山岩和外围砂砾岩中具有明显的铜铅锌矿化和异常。本文认为,在Tupiza铜矿床内,次火山热液成矿系统中心分布在蚀变次火山颈相中,富集铜(银)矿体;周边脉状-网脉状断裂-裂隙-蚀变带为铜铅锌成矿系统的过渡相带;而以赋存在上白垩统Aroifilla组第二岩性段中砂砾岩型铜(钴)矿体和Cu-Pb-Zn异常,为铜(钴)铅锌成矿系统的外缘相带。在深部围绕蚀变次火山岩相体具有寻找铜(银)、铜(钴)和铜铅锌矿体的潜力。
关键词:  Manto型铜矿  碱性火山岩  岩相地球化学  成岩成矿环境  玻利维亚Tupiza  矿产勘查工程
DOI:10.12029/gc20200204
分类号:P623
基金项目:国土资源部公益性行业科研基金项目(201511016-1)、中战会(北京)矿业科技有限公司项目(2014-032)、云南省矿产资源评价工程实验室(2010)和云南省地质过程与矿产资源创新团队(2012)联合资助。
Lithofacies geochemistry characteristics of alkali volcanic rocks and prospecting prediction in Tupiza copper deposit, Bolivia
DU Yulong1,2, FANG Weixuan3, LU Jia1
1.Kunming University of Science and Technology, Kunming 650093, Yunnan, China;2.Sinotech Minerals Exploration Co., Ltd., Beijing 100012, China;3.China Non-ferrous Metals Resource Geological Survey, Beijing 100012, China
Abstract:
In sediment-hosted copper deposits, altered volcanic rocks have special significance for diagenesis and mineralization. Based on the methods of tectonic lithofacies mapping, volcanic lithofacies classification, and electron microprobe analysis (EPMA), the authors studied lithofacies types of volcanic rocks, their geochemical characteristics, physical-chemical conditions of magmatic evolution and their relationship with copper (silver) enrichment. The following results show that mesogenetic intrusive facies, subvolcanic intrusive facies (sub-volcanic neck facies), volcanic overflow facies, pyroclastic facies and sink volcanic rocks are developed in the Tupiza copper deposit. The assemblage of rock types is diabase, gabbro, alkaline basalt, potash-trachybasalt, olivine basalt trachyandesite, and latite. In this area, alkaline basaltic magmatic emplacement has multiple stages and phases. In the Tupiza copper mining area, mineral geothermometer-geobarometer was used to do estimation. When the formation temperature and pressure of hornblende respectively are 630.97-748.43℃ and 55-251 MPa, the depth of diagenetic formation is estimated to be 2.04-9.27 km, revealing that the diagenesis evolution process under decreasing pressure-increasing temperature (decompression melting) and decreasing pressure-decreasing temperature had a high-temperature and high-oxidation diagenetic environment during magmatic decompression and emplacement, suggesting a multi-stage emplacement. Chlorite formation temperature is 112-305℃, lgf(O2)=-45.03—-56.68, lgf(S2)=-4.46—-18.07, suggesting a low temperature reduced diagenesis mineralization environment representing the main copper (silver) ore formation period. The Tupiza copper (silver) deposit was formed by the subvolcanic hydrothermal alteration diagenetic mineralization. Altered volcanic rock is a metallogenic material supply system for copper deposits. Copper (silver) orebody is concentrated in altered volcanic lithosphere and structural superposition, particularly concentrated in the intersection of NNE and NW-trending structures. In the pyrite glutenite at the top of the second lithologic section below the third lithologic alteration volcanic rock in the Upper Cretaceous Aroifilla Formation, the verifying drilling revealed a copper (cobalt) mineralized body, which was the sign of deep prospecting for hidden sedimentary rock type copper (cobalt) orebodies. In this paper, it is believed that, in the Tupiza copper deposit, the central phase of the sub-volcanic hydrothermal metallogenic system is distributed in the altered secondary volcanic neck phases, enriching the copper (silver) orebody. Peripheral veinlet vein-fractured-alteration zone is the transitional facies zone of the copper-lead-zinc metallogenic system, while the glutenite-type copper (cobalt) ore and Cu-Pb-Zn anomaly in the second lithologic zone of the Aroifilla Formation is the outer fringe facies zone of the copper (cobalt) lead-zinc metallogenic system. It has the prospecting potential for copper (silver), copper (cobalt) and copper-lead-zinc orebodies in the deep surrounding altered subvolcanic facies.
Key words:  Manto-type copper deposit  alkaline volcanic rocks  lithofacies geochemistry  diagenetic and metallogenic environment  Tupiza,Bolivia  mineral exploration engineering