东天山卡拉塔格成矿带红山铜-金矿床S同位素特征及成矿潜力研究

S Isotope characteristics of Hongshan Cu-Au Deposit,Kalatage Region,Eastern Tianshan,and Its Metallogenic Potential Analyisis

东天山红山铜-金矿床为卡拉塔格铜-金成矿带上新发现的两个铜-金矿床之一,大地构造位置上处于大南湖-突苏泉晚古生代岛弧带北段的中生代火山盆地中。容矿岩主要为流纹英安质火山碎屑岩,矿化与石英斑岩、流纹斑岩、次花岗斑岩密切相关,铜金矿化主要呈细脉浸染状和细脉状。该矿床处于东天山极端干旱少雨且稳定的荒漠地带,产有一系列复杂罕见的铁硫酸盐矿物。笔者研究了红山铜-金矿床具有代表性蚀变矿化的原生硫化物样品,其3δ4S值为+1.86‰^+5.69‰,平均值为3.70‰,绝大部分集中在+1.86‰^+3.20‰,且3δ4Scp小于δ34Spy,说明斑岩的成矿流体来自地幔,但却受到地壳的混染,成矿流体作用中S同位素分馏达到平衡。8种硫酸盐矿物的δ34S变化在2.15~6.73‰,平均值为3.74‰,与本矿床原生硫化物的3δ4S值+1.86‰^+5.69‰非常接近,说明该矿床的S源主要来自地幔流体,硫酸盐继承了母体硫化物的同位素组成。通过红山矿区岩芯矿化蚀变情况和激电剖面、激电测深以及Eh-4剖面资料分析,红山深部矿化异常体都具有低阻、中高极化的特征,Eh-4连续电导率剖面资料显示,深部450 m以下可能存在有隐伏的斑岩体,岩体顶部及周围为100~300Ω.m的低阻体,它极可能为铜矿的赋矿部位。因此,红山铜金矿区呈现出浅部(200~300 m以上)高硫化物型浅成-低温热液型金矿和深部(300 m以下)斑岩铜矿的成矿体系,具有寻找大型规模浅成低温热液-斑岩金-铜矿床的潜力。

Located in the Paleozoic uplift along the southern margin of Tu-Ha basin in eastern Xinjiang,the newly discovered Hongshan Cu-Au deposit occurs in the superimposed Mesozoic volcanic basin upon the north section of later Paleozoic Dananhu-Tousuquan accretionary arc.Kalatage Cu-Au orebelt is controlled by NWW-trend faults.The host rocks of Hongshan ore district are mainly rhyolitic-dacitic ignimbrites,whereas Cu-Au mineralization is closely related to quartz porphyry,rhyolitic porphyry and granitic porphyry.Mineralization styles are dominantly veinlet-disseminated and veinlet,occasionally stockwork.The mineral association is chalcopyrite,pyrite,bornite,chalcocite and sphalerite.Hongshan Cu-Au deposit,on the edge of the desert,is one of the driest areas in eastrn Tianshan.Oxidization zone of this deposit lies on the upper part of primary sulfide orebodies which are dominant in sulfate minerals.Sulfur isotope analyses show that δ34S values of pyrites vary in the range of ＋1.86‰~＋5.69‰,with an average of 3.70‰,mostly in the range of ＋1.86‰~＋3.20‰,and δ34Scpδ34Spy.Therefore ore-forming fluid of porphyry comes from mantle and was contaminated by the earth＇s crust.Sulfur isotope has reached balance in ore-forming process.Sulfur isotope analyses show that δ34S values of sulfates vary in the range of ＋2.15‰~＋6.73‰,with an average of ＋3.74‰,mostly equal to δ34S values of primary sulfides in Hongshan Cu-Au deposit.So supergene sulfates inherit sulfur of primary sulfide.According to analyses for the information of alteration and mineralization features of bore cores,induced activity polarization well logging and Eh-4 geophysical section,deep mineralization anomaly objects of Hongshan ore districts show low resistance,middle and high polarization,and measurements of Eh-4 consecutive conductance section show the existing of concealed porphyry ore bodies deeper than 450 m,on the top of and around rock body there are low resistance body ranged from 100-300 Ω·m,so this area may be the ore-bearing part.In a word,Hongshan Cu-Au deposit is a combine of upper HS-style epithermal Au deposit and deeper porphyry mineralization system.It has great potential to find large HS-style epithermal-porphyry Au-Cu deposits.