藏南扎西康锑硫盐多金属矿床成矿物质来源分析：兼论北喜马拉雅成矿带主要矿床矿质来源的差异性

The analysis of metallogenic material sources of the Zhaxikang antimony (sulfur salts) polymetallic deposits in Southern Tibet:Concurrent discussion on the differences of the ore sources of major mineral deposits in North Himalayan metallogenic belt

扎西康矿床是北喜马拉雅Sb-Au成矿带上一个较为特殊的大型-超大型锑硫盐多金属矿床,赋存于下侏罗统日当组。矿床容矿围岩以黑色含炭钙质板岩为主体,矿体严格受近南北向和北东向两组断裂控制,呈脉状、透镜状产出。矿石中金属矿物除闪锌矿、方铅矿、辉锑矿等常见硫化物之外,还大量发育硫锑铅矿、脆硫锑铅矿、黝铜矿、车轮矿等硫盐矿物;非金属矿物主要为菱锰矿、菱铁矿、石英和方解石,矿床的形成经历了中低温热液期和表生期。元素地球化学和硫、铅同位素研究表明,矿床中矿石和矿化岩石除富集Sb、Pb、Zn、Ag等主成矿元素外,还富含MnO、Cu、As、Cd、Au等矿化元素;容矿地层中Sb、As、Ag、Pb、Zn、Mn等成矿元素也较为富集,具备提供成矿物质的能力;矿石硫化物的硫同位素组成与容矿地层接近,指示成矿流体在运移过程中萃取了容矿地层中的Sb、As、Ag和S等组分,日当组为硫的主要提供者;铅同位素具变质结晶岩系特征,指示变质结晶岩系及与之有亲缘关系的淡色花岗岩为成矿提供了Pb、Zn等金属组分。北喜马拉雅成矿带主要典型矿床在矿质来源上存在着明显的差异,成矿带中部和北部的Sb和Sb-Au矿床的成矿物质主要来自于容矿地层和矿区岩浆岩(包括中生代中基性岩和新生代闪长岩),而在成矿带南部的Sb(-Au)-Pb-Zn矿床中,除容矿地层和矿区岩浆岩提供Sb、As、S之外,变质结晶岩系(拉轨岗日岩群)及与之有亲缘关系的淡色花岗岩也为成矿提供了Pb、Zn等金属组分。

The Zhaxikang deposit is a special super-large or large antimony （sulfur salts） polymetallic deposit, which occurred in Lower Jurassic Ritang Formation. Black carbon-bearing calcareous slates are served as the major ore-hosting wall rocks, while the ore-bodies are strictly controlled by south-north striking and north-east striking faults, with occurrences of veins and lenticular shape. This deposit had undergone epithermal and supergene stages during the mineralization. Thus, in additiorL to sphaterite, galena, stihnite and other common sulfides, the metallic minerals in ores of this deposit include some sulfur salts, such as boulangerite, iamesonite, tetrahedrite and bournonite. Non metallic minerals are rhodochrosite, siderite, quartz and calcite. The results of element geochemistry have shown that, in addition to the enrichment of major ore^forming dements （e. g. Sh, Ph, Zn and Ag） in mineralized rocks and ore of this mineral deposit, the mineralized elements, such as MnO, Cu, As, Cd and Au, are rich in these ore and rocks. Meanwhile, the oreforming dements, namely, SB, As, Ag, Ph, Zn and Mn, are also rich in orehosting strata, which can provide the material source for mineralization. For ore sulfides from the Zhaxikang antimony （sulfur salts） polymetallic deposits, their S isotopic composition are similar to the ones of ore-bearing strata, suggesting Sb, As, Ag, S and other components were extracted by ore-forming fluids during migration process, and that these sulfurwere mainly provided by the Ritang Pormatlon. Their Pb lsotopm coraposltlon shows the characteristics ot metamorphic crystalline rock series, suggesting that Pb, Zn and other metallic components were sourced from metamorphic crystalline rock series and leueogranites during the mineralization process. In North Himalayan raetallogenie belt, the ore sources of typical mineral deposits are of obvious differences. For the Sb and Sb-Au deposits occurred in the central and north parts of this rnetallogenic belt, the ore-Forming materials are sourced from ore-bearing strata and magmatic rocks; but for the Sg （ Au）-Pb-Zn deposits in the south part, in addition to Sb, Au and S that were derived from ore-hosting strata and magmatic rocks, the metamorphic crystalline rock series （Lhagoi Kangri group） and leucogranites also provided some ore-forming materials （for example, Pb and Zn） to the mineralization.