云南者桑金矿床载金矿物标型特征研究

Typomorphic characteristics of gold-bearing minerals in Zhesang gold deposit, Yunnan Province

者桑金矿床处在滇黔桂“金三角”构造带中，该矿床的形成经历了沉积成岩期、热液成矿期及表生氧化期，黄铁矿及毒砂为矿床的重要载金矿物。通过岩相学特征、标型矿物研究，发现热液成矿Ⅰ阶段中主要载金矿物为毒砂，热液成矿Ⅱ阶段为金矿化最主要阶段，主要载金矿物为黄铁矿。黄铁矿呈胶状、细粒状、破碎状；毒砂呈粗粒板柱状，维氏硬度偏低为其载金标型。晶胞参数测试表明，黄铁矿“值在5．4300～5．4325A之间，成矿Ⅰ阶段至成矿Ⅱ阶段“值逐渐变大。载金毒砂明显富S、C0亏As，导致b、c、β均低于理论值。各成矿阶段的黄铁矿及毒砂中主量、微量元素及硫同位素组成呈现一定变化规律，成矿物质主要来自于富含有机质的围岩。者桑金矿床为中低温热液矿床。

The Zhesang gold deposit located in the structural belt of Yunnan-Guizhou-Guangxi gold triangle structural belt. The formation of the Zhesang gold deposit experienced three stages, i.e., sedimentary diagenesis, hy-drothermal mineralization and supergenic oxidation. Pyrites and arsenopyrites are two major Au-bearing miner- als. Petrographic and typomorphic observations reveal that arsennopyrites were formed in the hydrothermal min- eralization Ⅰ phase （HM Ⅰ ） whereas pyrites in the hydrothermal mineralization Ⅱ phase （HM Ⅱ ）, which was the primary gold formation phase. The gold-bearing pyrites are colloidal, fine-gained or fragmentized, while the gold-bearing arsenopyrites are in the coarse columnar form. Both of them have low reflectance. Lattice parame- ter measurement indicates that the a of pyrite is 5. 4300～5. 4325 A, which gradually becomes larger from HM to HM Ⅱ, suggesting that As was concentrated in the hydrothermal mineralization stage. Gold-bearing ar- senopyrites are rich in S, Co and poor in As and, as a result, b, c and β are lower than their theoretical values.Similarities of geochemical and S isotopic compositions between pyrites and arsenopyrites imply that organic wall rock contributed most of the metallogenic materials. It is thus concluded that the Zhesang gold deposit is a mid- dle-low temperature hydrothermal deposit.