新疆阿希金矿矿床地质和地球化学研究  

Geology and geochemistry of Axi gold deposit,Xinjiang

作　　者：安芳[1] 朱永峰[1] 

机构地区：[1]北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室,北京100871

出　　处：《矿床地质》2009年第2期143-156,共14页Mineral Deposits

基　　金：国家自然科学基金创新群体项目(批准号40821002);国家科技支撑计划重点项目(2006BAB07B08)的资助

摘　　要：阿希金矿是新疆西天山产出的一个大型浅成低温热液型金矿,赋矿围岩为晚泥盆世火山岩,矿体以石英脉型为主,其热液成矿期由以下4个阶段组成:玉髓状石英阶段(Ⅰ),黄铁矿-石英脉阶段(Ⅱ),白铁矿-碳酸盐-石英脉阶段(Ⅲ),重晶石-碳酸盐脉阶段(Ⅳ),其中阶段Ⅱ和阶段Ⅲ是主要的金成矿阶段,银金矿为主要的含金矿物。从阶段Ⅱ〔195～285℃,logf(S2)=6.7～-13〕到阶段Ⅲ〔95～190℃,logf(S2)=-15.8～-25.6〕,成矿流体的温度和硫逸度明显降低。成矿流体与围岩作用导致流体中大离子亲石元素含量升高。阶段Ⅰ(δEu=1.17～1.52)和阶段Ⅱ(δEu=0.44～0.93)脉体的Eu异常和Eu含量区别显著,表明阶段Ⅱ成矿作用发生在相对还原的环境。阶段Ⅰ脉体具有轻稀土元素强烈富集而重稀土元素相对亏损的稀土元素配分模式(La/Yb=4.5～36.2),而阶段Ⅱ和阶段Ⅳ脉体轻重稀土元素分馏较弱(La/Yb=1.2～2.0),阶段Ⅳ重晶石-碳酸盐脉(∑REE=67.5×10-6)以较高的稀土元素含量而区别于阶段Ⅱ(∑REE=1.0×10-6～4.2×10-6),说明重晶石和碳酸盐矿物对REE的分异有重要影响。不同阶段脉体与围岩火山岩的地球化学特征表明,阶段Ⅰ成矿流体以与火山岩围岩有关的火山热液为主,进入阶段Ⅱ,大气水开始加入,引起成矿流体温度和硫逸度强烈降低,并导致金在阶段Ⅱ和阶段Ⅲ沉淀成矿。The Axi gold deposit is a large epithermal gold deposit in West Tianshan Mountain of Xinjiang. Its ore-forming process can he divided into four stages, namely, chalcedony quartz stage （ Ⅰ ）, pyrite-quartz stage （ Ⅱ ）, marcasite-carbonate-quartz stage （ Ⅲ ） and barite-carbonate stage （Ⅳ）. Electrum occurs as the most important gold-bearing mineral. Stage Ⅱ and Ⅲ are the major periods for gold deposition. From Stage Ⅱ [195-285 ℃, logf（S2 ） = -6.7-- 13] to Stage Ⅲ [95-190 ℃, logf（S2 ） = - 15.8--25.6], the temperature and sulfur fugacity of the ore-forming fluid decrease obviously. The reactions between the ore-forming fluid and the wall rocks caused the increase of LILE contents in the ore-forming fluid. The variations of Eu behaviors in veins formed at different stage suggest that Stage Ⅰ vein crystallized in a rather oxidized fluid relative to Stage Ⅱ vein. Stage Ⅰ vein is strongly enriched in LREE （La/Yb = 4.5-36.2） in comparison with veins formed at Stages Ⅱ and Ⅳ （La/Yb = 1.2-2.0）. Stage Ⅳ vein （∑REE ： 67.5×10^-6） is different from Stage Ⅱ vein （∑REE = 1.0×10^-6-4.2×10^-6）. CO3^2- and SO4^2- are important in transporting and enriching REE in the ore-forming fluid. Geochemistry of volcanic rocks and veins formed at different stage suggests that the magmatic fluid was the primary ore-forming fluid, and meteoric water participated in the mineralization from Stage Ⅱ to Stage Ⅳ, which caused obvious decrease of temperature and sulfur fugacity, and hence induced the electrum precipitation at Stages Ⅱ and Ⅲ.

关 键 词：地球化学 成矿阶段 阿希金矿 西天山 新疆 

分 类 号：P618.51[天文地球—矿床学] X753.03[天文地球—地质学]