新疆阿尔泰萨尔朔克多金属矿地质特征及成矿作用

Geological characteristics and metallogenesis of the Saershuoke polymetallic deposit in Altay,Xinjiang

萨尔朔克中型多金属矿主要赋存于潜流纹岩中,少量在阿舍勒组火山岩中。矿石呈致密块状、块状、条纹状、浸染状、细脉、网脉状和脉状构造,围岩蚀变主要是硅化、绢云母化和黄铁矿化,矿床的形成经历了喷流沉积期、潜火山热液期和表生期,金铜铅锌矿化形成于潜火山热液期的早成矿阶段。矿石中石英、方解石和绿帘石中流体包裹体划分为H2O-Na Cl型和H2O-CO2(±CH4/N2)-Na Cl型。主成矿阶段成矿温度集中于130~390℃,在350℃、310℃、190℃和140℃出现明显峰值;流体盐度集中于3.0%~10.0%Na Cleqv,密度0.56~1.03g/cm3。硫化物δ34S集中于-1.52‰~6.18‰,峰值为2.5‰,表明硫来自深源岩浆。石英δD介于-140‰^-103‰,δ18O SMOW值为6.9‰~8.5‰,δ18O H2O值为-4.03~0.94‰,表明主成矿阶段成矿流体是岩浆水混合深循环的海水。成矿时代为中泥盆世(382Ma),成矿作用与流纹斑岩有关。温度和压力的降低导致流体不混溶作用,同时流体成分的改变等在金铜铅锌成矿过程中起着主导作用。

The Saershuoke medium-size polymetallic deposit occurs in the rhyolite porphyry（ subvolcanic rock）,and some mineralization also occurring in the volcanic rocks of the Ashele Formation. The ores may have dense massive,massive,striated,disseminated,stockwork,and veinlet structures. Wall-rock alteration is well developed,mainly including quartz,sericite and pyrite.Based on cross-cutting relationships of the ore veins,mineral assemblages,paragenetic sequence and ore fabrics,the ore-forming process can be divided into three mineralization periods： exhalative sedimentary,subvolcanic hydrothermal and supergene. Early stage of mineralization in the subvolcanic hydrothermal period is main stage of gold,copper,lead and zinc mineralization. Two types of fluid inclusions,namely H2O-Na Cl and H2O-CO2（ ± CH4/ N2）-Na Cl types,have been recognized in quartz,calcite and epidote.Homogenization temperatures of fluid inclusions in the main stage mainly vary from 130 to 390℃,with peaks temperature of 140℃,190℃,310℃ and 350℃. Salinity mainly ranges from 3. 0% to 10. 0% Na Cleqv. Ore fluid densities range from 0. 56 to 1. 03 g / cm3.The δ34S values of sulphides associated with mineralization range from- 1. 52‰ to 6. 18‰ at a peak of 2. 5‰,indicating that the sulfur was derived from deep-seated magma. The δ18O SMOW values of quartz range from 6. 9‰ to 8. 5‰,with the corresponding δ18O H2 O values between- 4. 03‰ and 0. 94‰,and δD values of fluid inclusions between- 140‰ and- 103‰. The combined isotopic data imply that the ore-forming fluids of the main stage in the Saershuoke polymetallic deposit were mainly derived from magmatic fluids mixed deeply cycled seawater. Polymetallic mineralization in Saershuoke took place in the Middle Devonian（ 382Ma）,related to the rhyolite porphyry. The decrease of temperature and pressure,the immiscibility of ore-forming fluids,and the compositional variation of ore fluids played important roles in ore-forming processes of the Au-Cu-Pb-Zn ore bodies.