西天山Muruntau金矿床地质和S-Pb同位素示踪

Ore geology of Muruntau world-class gold deposit and S-Pb isotopic tracing

Muruntau金矿床位于乌兹别克斯坦卡拉库姆板块北缘,是世界规模最大的金矿床。赋矿地层为一套发生绿片岩相浅变质作用的含炭复理石建造。矿区主要经历了四期变形变质作用(D1-D4),矿体受构造控制明显,就位于桑格龙套-塔姆德套与穆龙套-道古兹套剪切带的构造交汇部位,金矿化主要产于次级韧脆性断裂中。对矿床的矿石硫化物及地层开展了系统S、Pb同位素研究,结果表明石英脉型及蚀变岩型矿石中硫化物的δ34S变化范围较大,集中于2.2‰~6.1‰,其中蚀变岩型矿石中毒砂样品δ34S值集中于2.2‰~4.6‰,含金石英脉中硫化物样品δ34S值集中于3.0‰~6.1‰,方解石-石英脉中硫化物样品δ34S值集中于3.5‰~4.0‰,表明矿石中硫主要来源于地层,可能有少量岩浆硫加入。2件黑色页岩中毒砂206Pb/^(204)Pb为19.906~20.378,^(207)Pb/^(204)Pb为15.730~15.750,208Pb/^(204)Pb为38.388~39.894;3件含金石英脉中黄铁矿206Pb/^(204)Pb为18.848~19.431,^(207)Pb/^(204)Pb为15.669~15.736,208Pb/^(204)Pb为38.346~38.879;2件方解石脉中毒砂206Pb/^(204)Pb为18.715~19.563,^(207)Pb/^(204)Pb为15.639~15.740,208Pb/^(204)Pb为38.640~39.295。6件地层岩石样品的铅同位素组成206Pb/^(204)Pb为19.416~20.600,^(207)Pb/^(204)Pb为15.675~15.746,208Pb/^(204)Pb为38.876~39.431。矿石铅与地层铅均落于上地壳与造山带之间,矿石铅显示较大的跨度,且与地层岩石铅具有部分重合,显示成矿物质具有双重来源,与赋矿地层及造山期变质流体均表现出密切成因联系。结合矿床地质特征总结分析,沉积地层的物质准备+多期构造运动驱动变质流体运移(D1-D4)+岩浆热液的后期叠加应该是Muruntau巨量金属富集的关键控制因素。

The Muruntau gold deposit may be the largest gold deposit in the world,which is located at the north margin of Karakum craton,Uzbekistan. Ore-hosted strata are carbonaceous flysch formation which underwent greenshist facies metamorphism. Four periodic deformation-metamorphisms（ D1-D4） occur in the ore district; the ore bodies were controlled by deforming zones and located in the intersection of the Sangruntau-Tamdytau and the Muruntau-Daugyztau shear zones. Gold mineralization occurs within secondary faults. Based on the systematic research of S and Pb compositions of sulfides and strata,it shows that the δ34S values of sulfides in the quartz vein and altered rocks range from 2. 2‰ to 6. 1‰. The δ34S values of arsenopyrite in the altered rocks range from 2. 2‰ to4. 6‰,the δ34S values of sulfides in the gold-bearing quartz vein vary from 3. 0‰ to 6. 1‰ and the δ34S values of sulfides in the calcite-quartz vein vary from 3. 5‰ to 4. 0‰,suggesting that the strata is the main source of sulfur and minor sulfur may be provided by magma.^（206）Pb /^（204）Pb ranges from 19. 906 to 20. 378,^（207）Pb /^（204）Pb from 15. 730 to 15. 750 and208 Pb /^（204）Pb from 38. 388 to 39. 894 for two arsenopyrite samples in the black shale.^（206）Pb /^（204）Pb ranges from 18. 848 to 19. 431,^（207）Pb /^（204）Pb from 15. 669 to 15. 736 and208 Pb /^（204）Pb from 38. 346 to 38. 879 for three pyrite samples in the ore-bearing quartz veins.^（206）Pb /^（204）Pb ranges from 18. 715 to 19. 563,^（207）Pb /^（204）Pb from 15. 639 to 15. 740 and208 Pb /^（204）Pb from 38. 640 to 39. 295 for two arsenopyrite samples in the calcite veins.^（206）Pb /^（204）Pb ranges from 19. 416 to 20. 600,^（207）Pb /^（204）Pb from 15. 675 to 15. 746 and208 Pb /^（204）Pb from 38. 876 to 39. 353 for six strata samples. The Pb-isotopic compositions of the ore and the strata show similar characteristics of the upper crust and orogeny. The broad range and some superposition with each other suggest that the metal in the gold mineralization derived from strata and metamorphic fluid. Combined with ore geology characteristics,material preparation of sedimentary strata ＋ fluid migration drived by multisuperimposed deformation（ D1-D4） ＋ superimposition of magmatic hydrotherm are the key factors controlling the gold mineralization in the Munruntau world-class gold deposit.