藏南柯月铅锌多金属矿床矿物标型特征及成矿物质来源

Mineral Typomorphic Characteristics and Sources of Ore-Forming Materials of Keyue Lead-Zinc Polymetallic Deposit,Southern Tibet

为了解藏南柯月铅锌多金属矿床主要矿物的标型特征及成矿物质来源,在详细野外及室内工作基础上对柯月铅锌多金属矿床进行了矿物电子探针和S-Pb同位素测定。柯月铅锌多金属矿床硫化物种类较多,电子探针分析结果显示,硫化物伴随的Cu、Ag含量较高。闪锌矿具有层控矿床特征,方铅矿及黄铁矿的标型特征表明其与沉积改造作用相关,同时也受到了岩浆及火山作用的影响。S同位素δ^(34)SCDT为4.9‰~11.2‰,与日当组地层S源范围相近,Pb同位素显示^(206)Pb/^(204)Pb比值为18.53~19.78,平均为19.589;^(207)Pb/^(204)Pb比值为15.674~15.939,平均为15.848;^(208)Pb/^(204)Pb比值为38.618~40.559,平均为40.155,与附近扎西康矿床的Pb同位素呈线性排列且放射性成因Pb较高,模式年龄均为负值,落入了北喜马拉雅和高喜马拉雅变质结晶岩系的印度地盾端元内,指示来源于上地壳。综上认为柯月铅锌多金属矿床具有沉积改造型矿床的特征;日当组地层及围岩对成矿提供矿源初始物质并且与扎西康特大型矿床成矿物质来源相似。

In order to understand the main mineral typomorphic characteristics and sources of Keyue lead- zinc polymetallic deposit, southern Tibet, electronic microprobe （EMP） and S-Pb isotope analysis have been conducted based on detailed field and lab work. The EMP analysis of many kinds of sulfide in Keyue lead-zinc polymetallic deposit, shows that the Cu and Ag content is higher in sulfide. The typomorphic characteristics of sphalerite share the same features with strata-bound deposits, whereas galena and pyrite indicate that it is a sedimentary deposit reformed by magmatic and/or volcanic activities. The range of δ^34ScDT（%0） is 4. 9‰- 11.2‰, similar to that of Ridang Formation. The 206Pb/204 Pb, 207pb/204 Pb and 208pb/204Pb of Keyue are 18.53-19.78 with an average of 19. 589, 15. 674-15. 939 with an average of 15. 848,38. 618-40. 559 with an average of 40. 155 respectively. Combined with Pb isotope composition of Zhaxikang deposit, they display a linear distribution and show high radiogenic lead content. The calculated model age is negative, falling into the north Himalayan and high Himalayan metamorphic rock series of In- dian shield. This indicates that the upper crust provides ore forming materials. Above all, Keyue lead-zinc polymetallic ore deposit has the characteristics of sedimentary transformation type ore deposit, while Ridang Formation and wall rocks are the sources of metallogenic material, which is the same as Zhaxikang deposit.