ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    四川丹巴独狼沟金矿成因矿物学及指针矿物学特征

    Genetic Mineralogy and Prospecting Mineralogy of the Dulanggou Gold Deposit in Danba, Sichuan Province

    • 摘要: 四川丹巴独狼沟金矿床位于扬子地块西缘,是近年来大渡河金成矿带中发现的一个大型金矿床。区别于典型的造山型金矿,独狼沟金矿中主要的载金矿物为碲铋矿物,在成矿带中也较为特殊,极具研究价值。为精细厘定独狼沟金矿的成因类型,明确矿床深部及外围的找矿方向,笔者从成因矿物学和指针矿物学的角度出发,通过电子探针(EPMA)和激光剥蚀–电感耦合等离子质谱仪(LA-ICP-MS)对独狼沟金矿中的黄铁矿、磁黄铁矿、闪锌矿进行微区化学成分分析,利用二阶聚类判别黄铁矿和磁黄铁矿的指针矿物标识特征。测试结果显示,黄铁矿中Ni和Se含量分别为0×10–6~991.72×10–6和32.42×10–6~131.02×10–6,平均分别为326.06×10–6和77.74×10–6;磁黄铁矿中Ni含量为13.90×10–6~647.62×10–6,平均为324.02×10–6;闪锌矿中Fe、Zn 平均含量分别为8.77%和54.24%。黄铁矿和闪锌矿的地球化学特征显示独狼沟金矿属于热液型矿床。矿物温度计表明独狼沟金矿成矿温度较高,属于中高温矿床。成矿主阶段的流体logfS2值为−11.6~−4.5,而logfTe2值为−13.0~−7.9。磁黄铁矿和黄铁矿均形成于石英–绢云母–磁黄铁矿阶段,但磁黄铁矿和黄铁矿中的Ni含量均具有较大差异,主成矿阶段来自深源的交代岩石圈地幔热液可能造成了部分磁黄铁矿和黄铁矿中Ni含量明显增高。因此,可将黄铁矿和磁黄铁矿作为独狼沟金矿的指示矿物。

       

      Abstract: Dulanggou gold deposit in Danba, Sichuan, located on the western margin of the Yangtze Block, it is a large-scale gold deposit discovered in the Daduhe gold metallogenic belt in recent years. Distinguishing from typical orogenic gold deposits, the primary gold-bearing minerals in Dulanggou gold deposit are tellurium-bismuth minerals, which are relatively unique within the metallogenic belt and of great research value. To precisely determine the genetic type of Dulanggou gold deposit and clarify the exploration direction in its depth and periphery, this paper, from the perspectives of genetic mineralogy and indicator mineralogy, conducted micro-compositional analyses of pyrite, pyrrhotite, and sphalerite in Dulanggou gold deposit using Electron Probe Micro-Analyzer (EPMA) and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). Additionally, second-order cluster analysis was applied to investigate the indicator mineral signatures of pyrite and pyrrhotite. The test results show that the content ranges of Ni and Se in pyrite are 0×10–6 to 991.72×10–6 and 32.42×10–6 to 131.02×10–6, with an average of 326.06×10–6 and 77.74×10–6, respectively; Ni in pyrrhotite is 13.90×10–6 to 647.62×10–6, with an average of 324.02×10–6; and in sphalerite, the average content of Fe and Zn are 8.77% and 54.24%. The geochemical characteristics of pyrite and sphalerite suggest that the Duolangou gold deposit is a hydrothermal-type deposit. The mineral thermometer indicates that the Duolangou gold deposit formed at a relatively high temperature, classifying it as a medium- to high-temperature deposit. The fluid logfS2 values during the main mineralization stage range from −11.6 to −4.5, while the logfTe2 values range from −13.0 to −7.9. Both magnetite and pyrite formed during the quartz-sericite-magnetite stage; however, the Ni content in magnetite and pyrite varies significantly. The deep-source magmatic hydrothermal fluids during the main mineralization stage likely contributed to the increased Ni content in some magnetite and pyrite. Therefore, pyrite and magnetite can be considered indicator minerals for the Duolangou gold deposit.

       

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