| 小秦岭金矿田地质特征及矿床成因 |
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| 引用本文：.1987.Geological Characteristics And Ore Genesis Of The Xiaooinling Gold Field[J].Mineral Deposits,6(1):56~67 |
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| 中文摘要:小秦岭金矿系产于太古界太华群中的含金石英脉型金矿。本文研究了小秦岭地层和岩浆岩中金的丰度，在建立太华群层序和该区重褶皱构造格局的基础上研究了含金石英脉展布规律、金矿脉的矿化特征与矿化阶段。根据含金石英脉切穿燕山早期岩脉等大量事实，认为金矿成矿时代为燕山晚期。通过对矿脉矿化特征、同位素地质特征、矿物标型特征、成矿物理化学条件及与晚燕山期二长花岗岩关系等研究，证明小秦岭金矿床属中低温中深岩浆热液矿床。 |
| 中文关键词:小秦岭金矿田 地质特征 含金石英脉 晚燕山期 岩浆热液矿床 |
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| Geological Characteristics And Ore Genesis Of The Xiaooinling Gold Field |
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| Abstract:Lying in area of Lingbao County a and Tongguan County, the Xiaoqinling gold field is of gold-bearing quartz vein type occurring in Aichaeozoic Taihua Group.The Taihua Group exposed in this area is a suite of metamorphosed intermediate-basic volcanic-sedimentary formation. The structural framework of the ore field comprises the regional fractures on the south and north sides and the refolded fold confined within them, with the places around the major axis of the refolded fold being the most concentrated locations of the gold-bearing quartz veins. Of the frequent magmatic intrusions in the ore field, the Late YanshaDian monzonitic granite is the largest intrusive body. The major ore veins are unexceptionally distributed 2-7 km fiom this granite body. There exist over one thousand gold-bearing quartz veins characterized by grouping or zoning as well as by parallel and equidistant distribution. They can be classified into pyrite type and polymetallic type. Ores are concentrated at intervals along the ore veins, generally having lengths of 30~300 m and vertical depths of 100-500 m or more with the ore grade being 6-16 g/t. Lacking of arsenopyrite seems to be a characteristic of the mineral composition. The gold mineralization during the hydrothermal activities might be divided into four stages, i. e., pyiite- quartz (I), quartz-pyrite (lI), polymetallic sulfides (m) and carbonate-quartz (IV) with the quartz-pyrite stage and the polymetallic sulfides stage playing the major role in mineralization. The formation temperature of minerals ranges from 303℃ to 155℃. Gold occurs mainly as native gold in the form of fracture gold, having the relative purity of 900-960. Such facts as the penetration of the gold-bearing quartz veins into the early Yanshanian diabase suggest that the Xiaoqinling gold deposit was formed during the Late Yanshanian period. An isotopic study of the gold ore vein yields an average δD of 45.54‰ and δ18O values from 8‰ to 11‰, showing the characteristics of a relatively normal magmatic water. The narrow variation range of δ34S values, together with the behaviors of sulfur similar to those of meteoritic sulfur, implies that sulfur was largely derived from the magma. Moreover, an examination of minor elements in pyrite and quartz also demonstrates the demonstrates the dominant role of magmatic hydrothermal fluids. It is therefore considered that the Xiaoqinling gold deposit is genetically medium-low temperature magmatic hydrothermal type. |
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