| 内蒙古毛登锡铜矿床地质及成因 |
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| 引用本文：.1996.Geology and origin of the Maodeng tin-copper deposit, Inner Mongolia[J].Mineral Deposits,15(2):133~143 |
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| 中文摘要:内蒙古毛登锡铜矿床是大兴安岭南段的锡多金属矿床之一。该矿床是与阿鲁包格山花岗斑岩(Rb-Sr等时线年龄149×l06 a，锶同位素初始比值为0.705)有关的具中等成矿深度和成矿温度的热液脉型锡铜矿床。矿床中主要产出锡矿体，它们分别以微脉、细脉和大脉的形式充填于自接触带向外的NW向断裂裂隙系统中。钾化（磁铁矿矿化）、云英岩化（锡石或辉钼矿矿化）和硅化（硫化物矿化）三个蚀变-矿化阶段流体的温度和氧、氢同位素值有同步降低之趋势，表明流体来自花岗斑岩的深部，并逐步向外接触带运移。 |
| 中文关键词:热液脉型锡铜矿床 地质特征成矿作用 内蒙古毛登 |
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| Geology and origin of the Maodeng tin-copper deposit, Inner Mongolia |
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| Abstract:The Maodeng tin-copper deposit is located 50 km northeast of Xilin Hot City, Inner Mongolia. On its outskirts there are well-developed Late Jurassic bimodal volcanic rocks, suggesting that this ore deposit might have been related to Yanshanian intracontinental rifting on the western slope of Da Hinggan Mountains. Within the ore deposit, acid volcanic rocks, porphyritoid granite and granite porphyry were successively formed and superimposed upon each other to produce a volcanic-intrusive complex. Detailed petrological, mineralogical and element geochemical data show that there existed the evolutionary trend of fractional crystallization among these three sorts of rocks, and that fractional crystallization of magma must have played the dominant role in the enrichment of tin in granitic melt and the subsequent formation of stanniferous granite-granite porphyry in the ore deposit. Controlled by the NW-trending fracture-fissure system, tin-copper orebodies in the Maodeng ore deposit assume vein bodies and are distributed exclusively from wall rocks west of the contact zone of the granite porphyry to NW-trending fractures and fissures in Early and Middle Jurassic conglomerate and sandstone. Nearly one hundred ore veins are en echelon arrangement, forming three ore vein groups. Potassic alteraiton (biotite, K-feldspar), greisenization (muscovite, topaz, fluorite, quartz) and silicification (quartz) are mainly developed within or around ore veins, with corresponding ore minerals being magnetite, cassiterite (molybdenite) and sulfides (chalcopyrite, sphalerite and pyrite). Tin orebodies are main orebodies in the ore deposit and are mostly distributed in greisen veins and quartz veins; copper orebodies mainly occur in quartz-sulfide veins on the outer side of the tin orebody, being not numerous in number. Homogenization temperatures of fluid inclusions fall into three ranges, i.e., 510~ 560℃, 310～450℃ and 200～350℃, corresponding respectively to three alteration-mineralization stages, namely potassic alteraiton (magnetite), greisenization (cassiterite) and silicification (sulfides). δ18O and δD values of fluids gradually decreased from potassic alteration stage through greisenization stage to silicification stage, suggesting that the gradual increase in meteoric water proceeded synchronously with the cooling of fluids. The above evidence reveals that, being a hydrothermal vein type tin-copper deposit related to granite porphyry, the Maodeng deposit was formed at medium depth (1.6~2.0 km) and moderate temperatures (450～200℃). Rb-Sr isochron age is l49×6 a, and initial ratio of Sr isotopes is 0.705, suggesting that stanniferous granite and ore deposit were formed later than Late Jurassic, and that magma contained materials from oceanic crust or upper mantle. |
| keywords:Hydrothermal vein tin-copper deposit, geological characteristics, ore-forrning process, Maodeng |
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