| 甘肃省玛曲大水金矿床地球化学特征 |
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| 引用本文：韩春明,袁万明,于福生,汤云晖,保增宽.2004.甘肃省玛曲大水金矿床地球化学特征[J].地球学报,25(2):127-132. |
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| 基金项目:国家自然科学基金项目(编号:40072068和10175076) |
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| 中文摘要:位于西秦岭川、陕、甘地区的大水金矿床是具有卡林特型的金矿床。矿床赋存于下三叠统马热松多组(T1m)灰岩和印支期花岗闪长岩脉中，矿化受到NWW向和近SN向断裂严格控制，矿石矿物以赤铁矿、自然金和黄铁矿为主，蚀变以硅化、绢云母化和褐(赤)铁矿化为特征。成矿作用可以分为原生成矿期和表生氧化一次生富集期。矿床成矿温度为100～400℃，盐度为2．70％～9．10％．，密度为0．875～970g／cm^3，成矿深度为1．422～3．555km。早期成矿流体来源于岩浆水，晚期成矿流体为改造的大气降水。硫同位素组成特征表明，该矿床成矿物质与矿区内花岗闪长岩有关，同时也有深部物质的参与。该矿床为多次构造-岩浆作用的产物，早期成矿作用发生于西秦岭碰撞造山期，晚期喜马拉雅期区域整体构造隆升使矿体金品位进一步提高，显示了该矿床多期次幕式成矿作用特征。 |
| 中文关键词:大水 金矿床 甘肃 玛曲 西秦岭 |
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| Geochemistry of the Dashui Gold Deposit in West Qinling Mountains, Gansu Province |
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| Abstract:The Dashui gold deposit is located in the south of West Qinling Mountains between Qinling orogenic zone and Songpan-Ganzi orogenic zone. The mineralization can be divided into the primary ore-forming stage and the supergene oxidation-secondary enrichment stage. Lying in the west Qinling orogenic belt,the deposit is controlled by the NWW-trending fault zone. The host rocks of the gold mineralization are mainly Triassic altered limestone and adamellite dikes. The δ 34 S values of pyrite range from -1.8 to +4.5 per mil with a mean of 2.40‰,reflecting a deep source of sulfur. Oxygen isotope data of calcite from ores indicate that calcite has δ 18 O values ranging from -22.4 to -11.1 per mil. The calculated δ 18 O water values of calcite range from -4.32 to +8.33 per mil and the δD values range from -61.1 to -101 per mil,suggesting that the ore fluids were mainly derived from the magma at the early stage of mineralization. Nevertheless,the values at the late ore-forming stage decrease,indicating the mixture of meteoric waters at the time of mineralization. Homogenization temperatures of fluid inclusions are relatively low,varying from 100 to 400 ℃ and mostly in the range of 150～200 ℃,with a peak value of 175 ℃. Salinities exhibit a wide range from 2.70 to 9.10 wt.% NaClequiv.,with a mean of 4.88 wt.% NaClequiv. In addition,the early gold mineralization occurred between 196 Ma and 182.8 Ma,and the late gold mineralization took place between 72.15 Ma and 41.21 Ma,as shown by the Rb-Sr isochron dating of inclusions from calcite in ores. This means that the Dashui gold deposit has at least two gold ore-forming stages. |
| keywords:Dashui gold deposit West Qinling Mountains Gansu Magu |
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