银岩斑岩锡矿的地质地球化学及其成因研究

GEOLOGY, GEOCHEMISTRY AND GENESIS OF YINYAN PORPHYRY TIN DEPOSIT

银岩斑岩锡矿产于花岗质岩浆演化晚期所形成韵浅成侵位的隐伏花岗斑岩小岩株中。花岗斑岩自下而上表现出强烈的蚀变分带:较新鲜的花岗斑岩(其中发育弱钾长石化)→黑鳞云母云英岩化→黄玉云英岩化→绢英岩化→顶部硅化核。矿化主要富集在黄玉云英岩化带。通过对矿物学、岩石学和微量元素等一系列地球化学特征的研究,作者认为银岩斑岩锡矿应属于华南陆壳改造型花岗岩类成岩成矿系列的斑岩锡矿。

The Yinyan porphyry tin deposit is a blind deposit associated with a small granite por-phyry stock. The petrology and geochemistry of the Yinyan granite porphyry suggest that it is genetically of transformation type, emplaced at the late stage of fractional crystallization within a highlevel magma chamber. Ore fluids appear to be derived predominantly from the granite magma and they intensely interacted with the wall rocks when finding their way upwards through the granite porphyry. From the lower part of the porphyry upwards the following alteration zones can be distinguished: (a) fresh granite porphyry, (b) protplithioniter quartz greisenization zone,, (c) topaz-quartz, greisenization zone, (d) sericite-quartz sericitiza-tion zone, (e) silicification zone (quartz core at the surface), Tin mineralization is related to greisenization, especially to topaz-quartz greisenization. Rock-forming and ore-forming temperatures and oxygen fugacities have been estimated, respectively. There are significant differences in many aspects between the Yinyan porphyry tin deposit and volcanic-subvolcanic porphyry tin deposits.