Geology, mineralization, and fluid inclusion characteristics of the Koitash redox-intermediate W–Mo skarn and W–Au stockwork deposit, western Uzbekistan, Tien Shan
Geology, mineralization, and fluid inclusion characteristics of the Koitash redox-intermediate W–Mo skarn and W–Au stockwork deposit, western Uzbekistan, Tien Shan
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DOI：
10.1007/s00126-019-00869-5
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发表时间：
2019-03
影响因子：
4.8
通讯作者：
S. Soloviev;S. Kryazhev
中科院分区：
文献类型：
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作者：
S. Soloviev;S. Kryazhev
天山金矿带的 Koitash W-Mo 矽卡岩矿床在蚀变夕卡岩中含有 60 kt WO3 资源（平均 0.56% WO3 和 0.029% Mo），在不同的物蚀岩带中还含有 42 kt WO3（平均 0.30% WO3、0.97 g/t Au、0.67% Cu 和 0.67% Cu）。 0.02% Bi）。它与早二叠世多相花岗闪长岩-花岗岩-淡色花岗岩岩体有关，该岩体由中至高钾、过渡准铝质到过铝质、弱氧化-弱还原、钛铁矿-钛矿系列花岗岩组成。该岩体位于一个具有推断古代大陆地壳的构造域中；后者，加上热软流圈物质可能的上升，很可能定义了在碰撞后环境中形成的独特的 W-Mo-Au 成矿组合。该矿床包括氧化还原中间顺行和逆行辉石-石榴石夕卡岩，部分被青盘岩和叶岩蚀变组合覆盖，包括白钨矿、辉钼矿、Cu-Bi-Ag-Te 硫化物和硫盐，以及天然 Bi 和 Au。 W-Mo 矿床（在晚期蚀变组合中含有 Au-W-Cu-Bi 矿化）与该地区同期侵入相关的以 Au 为主（含少量 W、Bi 等）矿床之间的成分相似性支持了它们可能的成因联系。流体包裹体数据表明，涉及不含碳的中等盐水（10.5–15.0 至 8.0–11.7 wt% 氯化钠当量）、高压（2000 至 1500 巴）、热（> 550–600 °C）水性流体，其源自结晶岩浆并形成顺钙质夕卡岩。该流体之后是中等含盐、富钙（14-16 wt% NaCl、19-21 wt% CaCl2）、低压（800 bar）流体，进入逆行矽卡岩阶段，沉积白钨矿、磁黄铁矿和辉钼矿，局部伴有少量萤石。丙烷石英-角闪石-绿泥石-寡长石-方解石，含有白钨矿、磁黄铁矿、局部辉钼矿，是由高甲烷含水碳流体在 370-400 °C 温度和 950-1000 bar 压力下沸腾形成的组合物。石质石英-绢云母-铁-碳酸盐，局部含有钠长石、萤石、绿泥石、白钨矿、辉钼矿和其他硫化物，还有 Bi 和 Au 矿物，蚀变组合最初由均匀的水-碳、低盐度流体在 365-370 至 300-315 °C 的温度和压力下形成，然后形成。 ~ 2000 条。δ34S 从逆行夕卡岩 (δ34S = + 2.0 至 + 2.3‰) 通过青绿岩 (δ34S = + 3.0 至 + 3.4‰) 增加到叶状蚀变 (δ34S = + 4.2 至+ 4.7‰）阶段。
The Koitash W–Mo skarn deposit in the Tien Shan Gold Belt contained resources of 60 kt WO3in altered skarn (averaging 0.56% WO3and 0.029% Mo) and an additional 42 kt WO3in separate zones of phyllic alteration (averaging 0.30% WO3, 0.97 g/t Au, 0.67% Cu, and 0.02% Bi). It is related to an Early Permian multiphase granodiorite–granite–leucogranite pluton that is composed of medium- to high-K, transitional metaluminous to peraluminous, weakly oxidized–weakly reduced, ilmenite–titanite series granitoids. The pluton was emplaced in a tectonic domain with inferred ancient continental crust; the latter, coupled with possible ascent of hot asthenospheric material, has likely defined a distinct W–Mo–Au metallogenic assemblage forming in a post-collisional environment. The deposit includes redox-intermediate prograde and retrograde pyroxene–garnet skarns, partially overprinted by propylitic and phyllic alteration assemblages, comprising scheelite, molybdenite, Cu–Bi–Ag–Te sulfides, and sulfosalts, as well as native Bi and Au. Compositional similarities between W–Mo deposits, containing Au–W–Cu–Bi mineralization in late alteration assemblages, and coeval intrusion-related Au-dominant (with minor W, Bi, etc.) deposits in the region support their possible genetic links. Fluid inclusion data indicate the involvement of carbonic-free moderately saline (10.5–15.0 to 8.0–11.7 wt% NaCl-eq.), high-pressure (2000 to 1500 bars), hot (> 550–600 °C) aqueous fluid, which was sourced from crystallizing magma and formed prograde calcic skarn. This fluid was followed by moderately saline, Ca-rich (14–16 wt% NaCl, 19–21 wt% CaCl2), lower pressure (800 bars) fluids toward the retrograde skarn stage, with the deposition of scheelite in association with pyrrhotite and molybdenite, locally with minor fluorite. Propylitic quartz–amphibole–chlorite–oligoclase–calcite, with scheelite, pyrrhotite, locally molybdenite, assemblages formed from boiling high-methane aqueous-carbonic fluids at temperatures of 370–400 °C and pressures of 950–1000 bars. Phyllic quartz–sericite–Fe–carbonate, locally with albite, fluorite, chlorite, scheelite, molybdenite, and other sulfides, also Bi and Au minerals, alteration assemblages initially formed from homogeneous and then from boiling aqueous-carbonic, low-salinity fluids at temperatures of 365–370 to 300–315 °C and pressures of ~ 2000 bars.δ34S increases from retrograde skarn (δ34S = + 2.0 to + 2.3‰) through propylitic (δ34S = + 3.0 to + 3.4‰) to phyllic alteration (δ34S = + 4.2 to + 4.7‰) stages.