| 中蒙边境沙麦-玉古兹尔地区钨和钨(钼)矿床地质特征, 形成时代和成因机理 |
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| 引用本文：聂凤军,胡朋,江思宏,刘翼飞.2010.中蒙边境沙麦-玉古兹尔地区钨和钨(钼)矿床地质特征, 形成时代和成因机理[J].地球学报,31(3):383-394. |
| DOI：10.3975/cagsb.2010.03.12 |
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| 基金项目:国家科技支撑项目(编号: 2007BAB25B02)；地质调查项目(编号: 1212010911029) |
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| 中文摘要:首次对横跨中蒙边境线的沙麦-玉古兹尔钨和钨(钼)矿化集中区代表性钨和钨(钼)矿床进行了系统研究。含矿花岗岩体锆石SHRIMP铀-铅同位素年龄为225.9±2.1 Ma, 钨(钼)矿石辉钼矿铼-锇同位素年龄为224±6.2 Ma, 二者具有明显的成因联系。无论是沙麦钨矿床, 还是玉古兹尔钨(钼)矿床, 其主要成矿期石英流体包裹体数据十分相似, 属中-高温度和中-低盐度NaCl-CO2±H2O流体。考虑到含矿花岗岩的?Nd(t)值均为正值, 同时结合其它地质证据, 可以推测, 钨和钨(钼)矿床是岩浆流体与大气降水相混合的产物。印支期中酸性岩浆活动不仅为成矿体系“注入”大量成矿物质, 而且为热液的对流循环提供了动力和热力来源。研究结果表明, 沙麦-玉古兹尔地区钨和钨(钼)矿床成矿作用与印支期构造-岩浆活动有关, 属与深成侵入岩有关的中-高温热液脉型金属矿床。 |
| 中文关键词:钨和钨(钼)矿床 地质特征 成因机理 玉古兹尔 沙麦 中蒙边境 |
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| Geological Features, Geochronology and Origin of the Tungsten and Tungsten (Molybdenum) Deposits in the Shamai-Yuguzer Mineralization Concentrated Camp along the Sino-Mongolian Border |
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| Abstract:Located on the western side of the southernmost part of the Mesozoic Da Hinggan Ling tectono-magmatic belt along the Sino-Mongolian border, the Shamai-Yuguzer area is the largest tungsten and molybdenum concentrated camp along the Sino-Mongolian border. During the Mesozoic Indosinian orogeny, intensive tectonic and igneous activities resulted in the large-scale granitoid magmatism in the Shamai-Yuguzer tungsten and molybdenum concentrated camp and its neighboring areas. The Shamai-Yuguzer granitoid batholith was emplaced in the Paleozoic and Mesozoic volcano-sedimentary sequences, controlled by NE- and NNE-trending fault zones. It has an outcrop area of 2700 km2, and consists mainly of porphyritic biotite granite and fine-grained biotite granite that have no difference in mineral assemblage. Rock-forming minerals are mainly quartz, microcline, microperthite and plagioclase associated with minor biotite and sericite. Accessory minerals are magnetite, apatite, zircon, sphene and allanite. The granitoid batholith is petrochemically characterized by relatively high SiO2, K2O, Rb, U and Th, and obviously low CaO, Fe2O3 + FeO, MgO, Sr, Ba, Ti, P and Eu, thus belonging to silicon-high and po-tassium-rich rocks of calc-alkaline series. Tungsten and tungsten (molybdenum) mineralization occurs within the Shanmai-Yuguzer granitoid batholith or along its contact with wall rocks in the forms of veins, veinlets and dis-seminated blocks. Ores consist of pyrite, chalcopyrite, molybdenite, scheelite, wolframite, K-feldspar, quartz, sericite, chlorite and epidote. As the most important economic minerals, molybdenite and wolframite occur in the forms of impregnation, radioflakes, thin films, aggregated flakes and veinlets in the veins. Re-Os isotopic data of six molybdenite separates defined a correlation line corresponding to an age of 224 ? 6.2 Ma, which is similar to the zircon SHRIMP U-Pb age (225.9±2.1 Ma) of the porphyritic biotite granite. Hydrothermal alterations in Shamai-Yuguzer show gross zonation of K feldspathization, greisenization, silicification, and propylitization from the porphyritic biotite granite outwards. Of these alterations, silicification and greisenization are well developed and have an intimate relationship with tungsten and molybdenum mineralization. Fluid inclusion studies yield homogeneous temperatures from 180℃ to 400℃, with the temperature of the main ore-forming stage ranging from 280℃ to 320℃. Gaseous inclusions are frequently co-existent with multiphase inclusions containing daughter minerals such as halite, sylvite, molybdenite and K feldspar. Intensive boiling of ore-forming fluid resulted in the deposition of a great volume of molybdenite, scheelite and wolframite under the circumstances of medium to high temperature, relatively low fO2 and fS2 as well as weak acidity. Sulfur and oxygen isotopic data of the molybde-num ore indicate that the ore-forming fluid was dominated by magmatic water at the early metallogenic stage, and was characterized by the mixture with magmatic water as the major source at the main metallogenic stage. By contrast, the ore-bearing fluid was mainly heated meteoric water. Therefore, it is conceivable that ore-forming materials were mostly derived from the magmatic source. The combined geochemical data, field geological ob-servations and petrological evidence indicate that the tungsten and tungsten (molybdenum) deposits or ore spots within the Shamai-Yuguzer mineralization concentrated camp are of hydrothermal vein type deposits or ore spots related to Mesozoic granitoid intrusions. It is believed that they are products of the Late Triassic intra-plate grani-toid magmatism along the NE-trending fault belt. Meanwhile, the genetic model and mineral exploration criteria of the Shamai and Yuguzer deposits can also be employed as useful tools during the comprehensive evaluation of concealed tungsten and tungsten (molybdenum) deposits on the western side of the southernmost segment of the Da Hinggan Ling tectono-magmatic belt along the Sino-Mongolian border. |
| keywords:tungsten and tungsten (molybdenum) deposit geological feature ore-forming process Yuguzer Shamai Sino-Mongolian border |
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