The Structure-fluid Flow Linkage Metallogenic Dynamics Of The Yangshan Gold Belt, Western Qinling Orogen, Central China

The Yangshan gold belt, located in the south subzone of western Qinling Orogen,is the biggest gold deposit in China. Through the comprehensive analysis ofgeological data, geological field work, microscopic thin section identification, fluidinclusion microthermometry, in situ Raman probe, geochemical testing, and couplingsimulation of structure-fluid, the dissertation studied the structural controlling, fluidflow and mineralization of this belt, and the main results are as follows.1. The gold belt occurred in the top of Wenxian arc tectonic belt, and controlledby Anchanghe-Guanyinba fault. The ore bodies are hosted in the Devonian Sanhekougroup and plagioclase porphyry veins; the alteration types are including silicification,carbonation, and sericitization; the minerals which are mainly pyrite, arsenopyrite,stibnite, and native gold, are mainly occurred associated with quartz veins.2. The mineralization occurred in190Ma that the late stage of collisionalorogeny and regional metamorphism. During the mineralization, the regionalprincipal compressive stress is mainly NE-striking which made lots of interbeddingfaults formed in the limbs of Caopingliang-Getiaowan anticlinorium which are themainly ore controlling structures that characterized by sinistral shearing.3. Two types of fluid inclusions were recognized in study area, includingaqueous and CO₂-bearing inclusions. The homogenization temperatures of fluidinclusions are mainly¹⁸0oC～280oC, and the salinities are≤12wt%NaC_lequ. TheH-O isotopic researches suggesting the ore-forming fluid is metamorphic water. Theore-forming fluid included lots of reducing gas, like N₂, CH₄, H₂S, and negative ionwhich are mainly Cl^-and SO₄^2-that indicating the Au was carried in （HS） and Cl^-complex.4. The trace elements of different type ores are similar to each other, such as theAu, Sb, As, and Hg are the enrichment elements, Cu and Mo are the loss elements.The above means all the ores formed in the same hydrothermal mineralization stage.The S, Pb, and Sr isotopic researches indicate the ore-forming material are fromDevonian Sanhekou group and Bikou group.5. The Yangshan gold belt is one of the largest disseminated epizonal orogenicgold belts that formed in the late stage of collisional orogeny which characterized bytectonic transformation from compression to extension in western Qinling. TheInteraction between NEE-striking faults and ore-forming fluid controlled theformation and distribution of ore bodies. The ore bodies are mainly occurred in theoccurrence changing places of the NEE-striking interbedding faults that formed in thelimbs of Caopingliang-Getiaowan anticlinorium.