豫西小秦岭东闯金矿床围岩蚀变研究

A STUDY ON WALL ROCK ALTERATION AT DONGCHUANG GOLD DEPOSIT IN XIAOQINLING MT. AREA, WEST HENAN

豫西小秦岭东闯石英脉型金矿床赋存于太古界太华群变质岩系中.本文研究了该矿的围岩蚀变类型、蚀变分带及各带的Au、Ag、Cu、Pb等成矿元素分布特征.探讨了围岩蚀变过程的温度、压力条件.用聚类分析、R型因子分析讨论了蚀变与矿化的关系,并比较了矿区两条不同矿化类型的主脉V.507和V.501在成矿作用方面的差别.

Dongchuang gold deposit is located in Xiaoqinling Mountain Area at the border between Henan and Shanxi province. The gold deposit consists of a series of hydrothermal veins emplaced in the faults striking east to west within the Precambrian metamorphic strata. The main metallic minerals associated with gold are pyrite, electrum, chalcopyrite, galena, sphalerite and native gold. Gangue minerals are dominantly quartz, and minorly sericite and calcite.The wall rocks surrounding ore-bearing veins are mainly hornblend plagioclasite, biotite plagioclase-gneiss and migmatite, and occasionally biotite granite and orthoclase porphyry at some veins. Field geology and observation from microsections showed that wall rock alteration were dominated by sericitization, silicification and pyritization, and chloritization, epidotization, carbonatization and biotitization were also found in some area. Four to five alteration zones can be divided in the different wall rocks, and Au, Ag and Pb concentration in the surrounding rocks decrease with the distance from the veins.The results of the cluster analysis and the factor analysis indicate that two of the largest orebearing veins, V. 507 and V. 501, are different not only in alteration types and mineral associations, but also in mineralzation of Au、Pb and other metal elements.