青海祁连郭米寺铜多金属矿床黄铁矿化学成分特征及其意义

Characteristics and Significance of the Chemical Composition of Pyrite from the Copper Polymetallic Deposit in Qilian County,Qinghai Province

郭米寺铜多金属矿床位于北祁连成矿带,属北祁连走廊南山成矿亚带的块状硫化物矿床.文章利用矿相显微镜及电子探针分析技术,对矿区内黄铁矿矿物组构及成分特征进行了研究,研究结果表明:本区黄铁矿呈自形-半自形粒状结构,多呈碎裂状,常被方铅矿及闪锌矿交代溶蚀形成骸晶、孤岛状等交代残余结构.Fe/S的比值范围为0.89~0.93(>0.875),表现出富Fe、亏S的特征;Co/Ni的比值范围为1.56~24.67,平均值为5.76.综合本矿床宏观地质特征及黄铁矿化学成分特征表明,郭米寺铜多金属矿床成因类型属与海相火山岩有关的火山喷气块状硫化物型矿床.

The Guomisi Copper Polymetalhc Deposit is located in the North Qilian metallogenic belt,which is a massive sul- fide deposit in the Nanshan corridor metallogenic sub belt of the North Qilian. The mineralogical characteristics and chemi- cal compositions of pyrites from the Guomisi Copper Polymetallic Deposit were studied by microscopic observation and elec- tron probe micro-analysis （EPMA） based on detailed field investigation on the geological characteristics of the ore deposit. The results show that the pyrite is euhedral to sub-euhedral granular texture, and are replaced by galena and sphalerite to form a skeleton- or island-shaped metasomatic residual texture. The results of EPMA show that the ratio of Fe/S in pyrite is from 0. 89 to 0.93 （ 〉0. 875）, showing the characteristics of Fe-rich and S-deficient; the ratio of Co/Ni in pyrite is from 1.56 to 24. 67, and the average value of ratios of Co/Ni is 5, 76. The macroscopic geological characteristics of the deposit and the characteristics of the chemical composition of the pyrite suggest that the Guomisi copper polymetallic deposit be a volcanic massive sulfide （VMS） deposit.