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摘 要：云南个旧锡多金属矿床接触带中的石榴石通过电子探针分析主要为钙铝榴石和钙铁榴石，含少量的镁铝榴石和锰铝榴石。从接触带内侧到外侧，石榴石中的Fe元素总体上具降低趋势，而Al和Mn元素具明显的增大趋势，Sn元素具弱的增大趋势，这主要与钙铁榴石成分的逐渐降低和锰铝榴石成分的逐渐增加有关。在接触带内侧的石榴石可见环状生长纹，Sn含量小于0.03%；在接触带外侧的石榴石可见环状分带构造，Sn含量为0.50%～0.55%。石榴石环状成分分带反映出成矿流体化学成分的波动性，这主要与岩浆期后热液在对围岩进行渗滤交代的过程中物理化学条件发生周期变化有关，在接触带外侧比内侧更有利于Sn的富集和沉淀。

关键词：石榴石；环带构造；矿物地球化学；电子探针分析；矽卡岩；渗滤交代；锡矿；云南

中图分类号：P59；P618.44 文献标志码：A

文章编号：1672-6561（2016）05-0578-09

Abstract： The electron microprobe analysis results show that the garnets in the contact zones between granite and carbonate from Gejiu Sn polymetallic deposit of Yunnan are mainly grossularite， andradite and a few of pyrope and spessartite. From the inner to outer contact zones， the content of Fe of garnet has the decreasing trend， but the contents of Al and Mn have the obviously increasing trend， and the content of Sn has the weakly increasing trend. The trend is mainly related to the decrease of andradite in the inner side and the increase of spessartite in the outer side. The content of Sn of garnet with ring growth lines in the inner contact zone is less than 0.03%； the content of Sn of garnet with zonal structure in the outer contact zone is 0.50%-0.55%. The ring growth lines and zonal structure of garnet imply the chemical composition volatility of metallogenic fluid. It is related to the periodicity change of physical and chemical conditions in post-magmatic hydrothermal infiltration metasomatism between granite and surrounding rocks. Compared with the inner contact zone， the outer contact zone is more favorable to the enrichment and precipitation of Sn.

Key words： garnet； zonal structure； mineral geochemistry； electron microprobe analysis； skarn； infiltration metasomatism； Sn deposit； Yunnan

0 引 言

石榴石在不同类型的变质岩、花岗岩、伟晶岩、酸性火山岩、金伯利岩和一些交代岩中较为常见。钙铝榴石主要产于不纯的钙质岩受热液变质或区域变质的岩石中，也可产在钙质交代的岩石中；钙铁榴石通常产于接触带或不纯的钙质岩受热液变质后的岩石中，特别是在与这种变质作用有关的交代矽卡岩矿床中[1]。梁祥济在实验室合成出了钙铝-钙铁榴石及它们之间的过渡性矿物[2]。前人对不同产状中的石榴石及其成分环带已进行了大量的研究[3-17]。在云南个旧锡多金属矿床花岗岩与碳酸盐围岩的接触带中，石榴石矿物为一种较为常见的硅酸盐矿物。……