| 甘肃省玛曲大水金矿床地球化学特征 |
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| 关键词:Dashui gold deposit West Qinling Mountains Gansu Magu |
| 基金项目:国家自然科学基金项目(编号:40072068和10175076) |
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| Geochemistry of the Dashui Gold Deposit in West Qinling Mountains, Gansu Province |
| 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. |
| HAN Chun-ming,YUAN Wan-ming,YU Fu-sheng,TANG Yun-hui,BAO Zeng-kuan.2004.Geochemistry of the Dashui Gold Deposit in West Qinling Mountains, Gansu Province[J].Acta Geoscientica Sinica,25(2):127-132. |
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