关键词: 毒砂, 标型特征, 八克金矿, 微量元素, 稀土元素, 黔东

Abstract:

The Bake gold deposit is characterized by high richness in gold in ore body and widely distributed arsenopyrite in surrounding rocks, which make a clear distinction with other gold deposits of this area. Based on the analysis of the geological background, regional geological conditions of mineralization, oreforming mechanism, by applying theories and methods of minerageny and prospecting mineralogy, using the modern testing technology, the typomorphic characteristics of arsenpyrite in the Bake gold deposit were studied in this paper, achieving important information on the genesis of ore deposits from the view of another point. The results show that goldbearing arsenopyrite in ore bodies have the features of small size, poor crystallinity, unit cell parameters close to the theoretical value, Ntype thermoelectricity, and the mean value of -1956 μV/℃ for pyroelectric coefficient which is significantly lower than that of arsenopyrites adjacent to the surrounding rocks (-1851μV/℃)  and that far away from the surrounding rocks (-1746μV/℃). For the chemical compositions, S/As is more than 1, and Fe /(As+S) is less than 05. From the morphology by electron probe observation, arsenopyrite particles are relatively broken, fractures develop, and galenas are filling being associated minerals. The results of rare earth elements and trace elements indicate that, REE contents in arsenopyrite of ore body are obviously lower than those of surrounding rock, and show strong Eu negative anomaly. Ore forming fluids are rich in chalcophile elements and LREEs, lose HFSEs, belong to a fluid system with weak deoxidation and rich Cl. Through the study on Y/Ho, Zr/Hf, Nb/Ta and Co/Ni ratio, Bake gold deposit is inferred to be a magmatic hydrothermal type deposit with medium temperature.

Key words: arsenopyrite, typomorphic characteristics, Bake gold deposit, trace element; , REE, Eastern Guizhou Province