甘肃阳山金矿碳氢氧同位素与成矿流体来源  

The C-H-O isotope systematics of the Yangshan gold deposit,Gansu and its implication for the ore-fluid origin.

作　　者：李晶[1,2,3] 陈衍景[2] 李强之 毛世东[1,4] 秦艳[1] 郭俊华 南争路 杨荣生[2] 

机构地区：[1]中国科学院广州地球化学研究所成矿动力学重点实验室,广州510640 [2]北京大学造山带与地壳演化重点实验室,北京100871 [3]中国科学院研究生院,北京100049 [4]武警黄金部队指挥部,北京100102

出　　处：《岩石学报》2008年第4期817-826,共10页Acta Petrologica Sinica

基　　金：国家973计划2006CB403500项目;国家自然科学基金项目(No.40703010、40730421、40425006);科学院百人计划项目和武警黄金部队科研项目的资助

摘　　要：甘肃文县阳山金矿的探明黄金储量已达308t,平均品位4.74g/t,是我国地质勘查储量最大的金矿床。该矿床产于西秦岭造山带,是一个同碰撞形成的类卡林型金矿床,矿体受EW向韧脆性剪切带控制,赋矿围岩为泥盆系碳质千枚岩-板岩-碳酸盐-硅质岩和侵入其中的花岗斑岩脉。热液石英的流体包裹体之δ^(13)C_(CO_2)(PDB)值为-2.5‰～-5.6‰,δ^(87)C_(CH_4(PDB))值为-23.1‰～-32.6‰,说明成矿流体来源于碳酸盐地层或相似岩石建造的变质或/和改造脱水作用。该结论尚被流体氢氧同位素研究结果所证明,成矿早阶段和主阶段流体的δ^(18)O_W值介于9.5‰～15.3‰,δD_W值为-86‰～-73‰。两件矿化晚阶段流体的δ^(18)O_W氧分别为2.7‰和6.8‰,表明有强烈的大气降水热液混入。总体而言,成矿流体系统从早到晚、从深到浅,由变质热液演变为大气降水热液。特别补充说明,上述研究结果和认识与我们根据流体包裹体和矿床地质研究得出的结论相吻合。The Yangshan gold deposit, Wenxian county, Gansu province, containing 308 t Au with average grade of 4.74g/t, is now ranked as the China＇ s largest gold deposit. Locating in western Qinling Orogen, central China, it is a syn-collisionally formed Carlin-like gold deposit, Its orebodies are controlled by an east-trending shear-zone and hosted in the Devonian carbonaceous carbonate-phyllite-slate sequence or the granite-porphyry dikes intruding into the Devonian strata. The δ^13 CCO2（PDB） and δ13 CCH4（ PDB） ratios of fluid inclusions within quartz separates range -2.5‰ ～ -5.6‰ and -23.1‰ ～-32.6‰, respectively, suggesting that the ore-flulds have been mainly sourced, through metamorphism and/or reworking, from the Devonian strata or/and similar lithologies which comprise carbonaceous phyllite, slate, chert and carbonate. This conclusion is strongly supported by the δ^18O values of the early- and main-stage ore fluids, which range from 9.5‰ to 15.3‰, with corresponding δD values between - 86‰～ - 73‰. Two δ^18 O values of late oreforming stage oreluids are 2.7‰ and 6. 8‰, implying a significant input of meteoric water. In general, the ore-forming fluid-system varies from early, deep, metamorphic fluid to late, shallow, meteoric water. It is worthy of stating that the above results and understandings are consistent with conclusions drawn from our studies of fluid inclusions and ore geology.

关 键 词：阳山金矿 碳氢氧同位素体系 成矿流体 秦岭造山带 

分 类 号：P597.2[天文地球—地球化学] P618.51[天文地球—地质学]