| 新疆哈密马庄山金矿成矿流体成冈及金沉淀机制的探讨 |
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| 引用本文：.2000.Genesis of ore-forming fluids and precipitation mechanism of gold in the Mazhuangshan gold deposit, Hami, Xinjiang[J].Mineral Deposits,19(3):193~200 |
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| 基金项目:国家305项目（96-15-05-05）专题 |
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| 中文摘要:马庄山大型金矿位丁阿齐克库都克东部，分布有中晚石炭世的中酸性火山岩及相应的次火山岩。近20条矿体产于其中。矿石平均品位为6. 4×10-6。成矿流体均一温度的峰值在240 ~ 260℃，成矿深度为1.6～2.3 km，具有浅成成矿的特点。成矿流体成分摩尔浓度比值mK+／mNa+ (0.10 ~ 0.81)、m2Na+／mCa2+ (0.001~ 0.338)、m∑Cl/ m∑S和m∑C／m∑S等比值，成矿条件参数pH值为5.8 ~ 7.4, 氧逸度(fO2) 1.9×10-55 ~ 2.9×10-47 Pa，硫逸度（fs2）约为10-13Pa; Eh值为-0.6 eV流体δ34S值为+3.94‰ ~ +4.98‰，均随还原参数Hy [Hy=(CO+ CH4) /CO2]和温度有规律变化。且矿石和脉石中的金含量也与Hy成正比。矿石和脉石REE配分图和微量元素特征与岩浆岩相似，代表着成矿物质来源与围岩岩浆岩关系密切。推断岩浆来源的成矿流体经地下水的混合作用是全沉淀的重要机制。 |
| 中文关键词:成矿流体 石英斑岩 成矿机制 新疆马庄山金矿 |
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| Genesis of ore-forming fluids and precipitation mechanism of gold in the Mazhuangshan gold deposit, Hami, Xinjiang |
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| Abstract:Mazhuangshan area is the east part of Aqikekuduk island arc, where Middle-Late Carbonife rous interm ediate-acid magmatic rocks occur. There are more than twenty ore-bodies in the district with an average gold grade of 6.4×10-6. The dominant metallic minerals are native gold, gold argentid, native silver, pyrite and galena. Pyrite is the main gold carrier characterized by high Fe and low S. W allrock alteration mainly includes pyritization, silicification and sericitization. Carbonation w as extensive at the late stage, frequently forming high-grade orebodies. Three ore-forming stages maybe distinguished. The peak values of homogenization temperatures of primary fluid inclusions range from 240 to 260℃. Mine ralization pressures and depths are 47.2 ~ 68. 8 MPa and l.6 ~2.3 km respectively, showing ore-forming features of a hypergene gold deposit. Salinities of fluid inclusions range from 6.2 % to 21% NaCl equivalent, averagely 15% NaCl equivalent. Fluid inclusion geochemistry shows that Ca2+ concentration is much higher than Mg2+. The mK+/mNa+, m2Na+/mCa2+ (0.001 ~ 0.338), m∑Cl/m∑S and m∑C/m∑S ratios vary with the reducing parameter [ Hy= (CO+ CH 4) /CO2 ] and temperature. The gold content of ores and gangues is in positive correlation with Hy. The pH values of inclusion water of quartz range from 5.8 to 7.4, Oxygen fugacity (fO2) are 10-55 to 10-47 Pa, sulphur fugacity (fS2) is about 10-13 and Eh values are estimated to be about -0.6 eV. δ34S values of the fluids range from +3.9‰ to +5.0‰, With a mean of 4.5‰. 206Pb/204Pb, 207Pb/208Pb and 208Pb/204Pb ratios of chalcopyrite are 18.269 ~ 18.352. 15.550 ~ 15.633 and 38.077~ 38.355 respectively. ∑REE values (4.7×10-6~ 43.1×10-6) of ores and gangues are obviously lower than those of the host magmatic rocks, but their REE and trace element web diagram s are similar to those of host magmatic rocks, suggesting that the solution consisted dominantly of meteoric water mixed with some magmatic water, and that metallogenic elements mostly came from magmatite. The deposit is intimately related to host magmatic rocks. Gold in hydrothermal ore fluids migrated mainly in the form of gold sulfide complexes dominated by HAu(HS)2 and Au(HS)2. Mixing of cooler ground water was probably the most effective mechanism for the precipitation of the ore-forming materials. The deposit is classified as the Middle-Late Carboniferous shallow-seated mesothermal-hypothermal gold deposit. |
| keywords:metallogenesis, quartz porphyry, ore-forming mechanism, Mazhuanshan gold deposit |
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