桂西北丹池成矿带主要金属矿床成矿特征及成矿规律

Metallogenic characteristics and ore_forming regularity of metallic deposits along Nandan_Hechi metallogenic belt in northwestern Guangxi

桂西北丹池成矿带是中国重要的有色金属成矿带之一,主要由芒场、大厂、五圩3个矿田组成。文章通过系统的地质调查和综合研究,总结了丹池成矿带主要金属矿床的成矿地质特征,以及矿床的成矿条件和成矿规律研究的新进展;论证了带内重要的多金属矿床为岩浆热液成因。带内燕山晚期花岗岩为高钾钙碱性、过铝质系列的含锡花岗岩,它具有高硅、高碱、贫钙、贫镁的特征;其在成因上为大陆地壳重熔的"S"型,可能源于桂北元古界四堡群或更老构造层的重熔,但也有幔源物质的混入。3个矿田中矿化的分带性明显,以花岗岩隆起为中心向外,矿化组合表现为高温W_Mo矿化、Zn_Cu_Sn矿化→高中温Sn多金属矿化→中低温Pb_Zn矿化→低温Sb_Hg_As矿化。成矿与成岩同期,成矿物质主要来自岩浆,部分来自赋矿的泥盆系;成矿流体早期以岩浆水为主,晚期有较多的大气降水的加入。同时,利用"缺位找矿"的思路,预示在研究程度相对较低的五圩矿田深部有较大的找矿潜力。

The Nandan-Hechi metallogenic belt,consisting of Mangchang,Dachang and Wuxu orefields,is one of the important nonferrous metal metallogenic belts in China.Based on detailed investigation and comprehensive study,the authors summarized metallogenic features of main polymetallic ore deposits in the Nandan-Hechi metallogenic belt and recent new achievements in the aspects of metallogenic conditions and regularities and,on such a basis,pointed out that the important polymetallic deposits belong to magmatic hydrothermal origin.Granites formed in Late Yanshanian period are high-K calc-alkaline series peraluminous granites with the characteristics of high silicon,high alkaline,poor Ca and Mg.Genetically,they belong to the continental crust remelted “S” type and might have originated from remelting of Proterozoic Sibao group or older tectonic layer in northern Guangxi,with the addition of some mantle material.The mineralization in the three orefields have clear zonation.With the granite uplift as the center,from the inside to the outside,the mineralization assemblages show high-temperature W-Mo metallization,Zn-Cu-Sn metallization→high-medium temperature Sn polymetallic metallization→medium-low temperature Pb-Zn metallization→low temperature Sb-Hg-As metallization.Mineralization and diagenesis took place in the same period.Ore-forming materials were derived mainly from magma and subordinately from Devonian ore-bearing strata.The early ore-forming fluids came mainly from the deep magma,with the addition of atmospheric water at the late stage.Using the “vacancy” theory,the authors made the prediction that the Wuxu orefield has a great ore potential in the depth.