| 甘肃北山红尖兵山钨矿床地质特征及成矿物质来源 |
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| 引用本文：.2004.Geological Features and Ore_forming Material Sources of Hongjianbingshan Tungsten Deposit in Beishan Mountain, Gansu Province [J].Mineral Deposits,23(1):11~19 |
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| 基金项目:国家自然科学基金项目(编号：40073015)和国家地质调查项目(编号：K1.3.32) |
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| 中文摘要:对甘肃北山红尖兵山钨矿床地质特征进行了总结，同时，对代表性钨矿石样品中的黑钨矿进行了Sm_Nd同位素测定。研究表明，红尖兵山钨矿床的矿化类型大体可划分为云英岩型和黄玉_石英脉型。钨矿化的发生时间为海西期(322～260 Ma)，其中云英岩型钨矿石的形成时代略早于黄玉_石英脉型矿石。云英岩型钨矿石中2件黑钨矿样品的εNd(322 Ma)值分别为5.93和4.24，与同时期亏损地幔钕同位素演化线值接近。相比之下，黄玉_石英脉型钨矿石中5件黑钨矿样品的εNd(322 Ma)值变化范围为-4.16～-8.05，与同时期古大陆壳钕同位素演化线值相似。云英岩型钨矿石的形成作用与亏损地幔源岩浆活动有关，而黄玉_石英脉型钨矿石则很可能是壳源岩浆活动的产物。这一推论对于揭示本区钨矿床成矿作用本质和指导隐伏矿床找矿工作具有重要意义。 |
| 中文关键词:地球化学 黑钨矿 钕同位素组成 成矿物质来源 红尖 兵山 甘肃北山 |
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| Geological Features and Ore_forming Material Sources of Hongjianbingshan Tungsten Deposit in Beishan Mountain, Gansu Province |
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| Abstract:Located in the western part of the Hongshishan_Heiyingshan terrane within the Kazakhstan_Beishan plate, the Hongjianbingshan deposit is one of the most important tungsten deposits in northwest China. Tungsten mineralization occurs mainly as topaz_quartz veins within rhyolite tuff and rhyodacite of Early Carboniferous Baishan Formation, and partly as massive and layered greisens in Hercynian monzogranite stocks, controlled by a number of NE_trending fracture or fault zones. Individual tungsten bodies can be traced along strike for 120 to 420 m, and downdip for 800 to 1200 m, with thicknesses ranging from 0.19 to 1.32 m. Alterations related to tungsten mineralization consist mainly of greisenization, silicification, albitization, sericitization, K_feldspathization, epidotization and skarnization, with greisenization and albitization being most important. Ore minerals are relatively simple, and mainly include wolframite, cassiterite, molybdenite, bismuthinite, galena, sphalerite, sheelite, chalcopyrite, pyrite and magnetite. Gangue minerals consist of quartz, topaz, helvine, K feldspar, albite, muscovite, sericite, fluorite and calcite. The WO3 content of the W_bearing topaz_quartz veins and that of greisen blocks range from 1.23% to 1.86% (1.55% on average) and 0.26% to 0.54% (0.40% on average) respectively. Researches on regional ore_forming process show that the major tungsten ore_forming event of the deposit occurred during the early Hercynian orogeny (322 Ma). Seven wolframite separates from both topaz_quartz vein type and greisen block type tungsten ores were selected for Sm_Nd analysis. The εNd (322Ma) values of two wolframite separates from the greisen massive ore range from 4.24 to 5.93, much higher than values of the ancient continental crust and Precambrian metamorphic rocks. In contrast, the εNd (322 Ma) values of five wolframite separates from the topaz_quartz vein ores range from -4.16 to -8.05, much lower than values of the greisen massive ore. Geochemical data, isotopic data and petrological observations all indicate that the greisen ores might have been formed by the mantle_related ore fluids, while the topaz_quartz vein ores were probably derived from crustal_derived magma fluids. The Hongjianbingshan tungsten deposit is believed to be a product of early Hercynian igneous process along the northern margin of the Kazakhstan_Beishan plate. Meanwhile, the genetic model and mineral exploration criteria of the Hongjianbingshan deposit can also be used as useful tools for comprehensive evaluation of concealed tungsten deposits in the Beishan Mountain, Gansu Province. |
| keywords:geochemistry, wolframite, Nd isotopic data, source of ore_forming materials, Hongjianbingshan, Beishan, Gansu |
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