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    南秦岭略阳干河坝金矿床地质地球化学特征

    Geological and geochemical features of the Ganheba gold deposit, Lueyang, South Qinling

    • 摘要: 提要:干河坝金矿床是秦岭勉县—略阳构造混杂岩带内发现的首例金矿床。矿床形成经历了前勉略洋沉积建造及基底形成阶段、勉略洋盆沉积预富集阶段、秦岭与扬子板块间陆-陆碰撞拼合和造山后派生出构造叠置改造富集阶段。有利的含矿岩系(含Au 3.66×10-9)是金矿形成的物质基础,韧-脆性递进构造变形作用是金成矿的关键控制因素;干河坝金矿为两者叠加的重要产物。矿床主成矿期均一温度137~280℃,具有中—低温热液成矿特征;早—中成矿阶段成矿流体盐度(NaCl)变化于4.5%~23.1%。硫同位素以富集重硫为特征,δ34S值为9.91‰~15.45‰,除火山成因硫强烈分馏外,还有大量沉积岩系地壳硫的加入,显示后期地质改造强烈的成矿作用特点。金呈显微细粒的独立矿物,成矿元素组合为Au-Ag-As-Sb-Cu-Pb-Zn,显示蚀变构造岩外貌的类卡林型金矿床地质特征。

       

      Abstract: Abstract:The Ganheba gold deposit is the first gold deposit found in the Mianxian-Lueyang tectonic mélange belt of the Qinling orogenic belt. The formation of the gold deposit went through the phase of deposition of sedimentary rocks and formation of the basement in the pre-Mianxian-Lueyang restricted ocean, the phase of gold preconcentration in the sediments of the Mianxian-Lueyang restricted ocean and the phase of continental collision and amalgamation between the Yangtze plate and Qinling plate and structural stacking and reworking and gold concentration derived after orogeny. Favorable host rocks (containing 3.66×10-9 Au) is the material basis for gold mineralization and ductile-brittle progressive structural deformation is the key ore-controlling factor. The Ganheba gold deposit is the product of the combined action of the rocks and the structure. Fluid inclusion study shows that the homogenization temperatures of the ore fluids ranged from 137 to 280℃ in the main mineralization stage of the deposit, which shows the features of mesothermal-epithermal mineralization. The salinities ranged from 4.5 to 23.1wt% NaClequiv. at the early to middle stages of mineralization.The δ34S values of pyrite ranged from +9.91 to +15.45‰, showing the feature of enrichment in heavy sulfur. The sulfur of volcanic origin shows strong fractionation, and in addition, crustal sulfur from sedimentary rocks was also introduced, showing the feature of the mineralization that underwent strong geological reworking in the late phase. Gold occurs mainly as independent microgranular minerals and the paragenesis of ore elements are Au-Ag-As-Sb-Cu-Pb-Zn, showing the geological features of a Carlin-like gold deposit.

       

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