广西龙头山金矿床地质特征及成矿分析

Geological Characteristics and Metallogenic Analysis of the Longtoushan Gold Deposit in Guangxi Province

龙头山金矿床产于一个中生代残留火山颈构造中,火山颈周围的地层主要为下泥盆统莲花山组和寒武系黄洞口组。矿体呈细脉浸染状和脉状产于次火山岩筒与周围地层的内外接触带上。围岩蚀变主要有电气石化、硅化、钾长石化、黄铁矿化、绢云母化、高岭土化和绿泥石化。金矿化与硅化和黄铁矿化密切相关。流体中氧同位素组成反映了流体系岩浆水与大气降水混合成因。硫同位素特征表明矿床矿液中硫是多源的,主要来自火山-侵入杂岩及基底地层。据铅同位素特征推测铅主要来自中生代火山岩,部分来自基底地层。该矿床的成矿物质主要来源于深部岩浆和部分基底地层。成矿温度在215～260℃之间,属中-低温次火山期后热液型金矿。

The Longtoushan gold deposit occurs in a Mesozoic residual volcanic neck.The main strata around the neck are Lianhuashan group of Lower Devonian Series and Huangdongkou group of Cambrian System.Displaying veinlet disseminated type and vein type,the ore bodies are found in the sub-volcanic rock pipe and internal or external contact zone of surronding strata.The wall-rock alteration have tourmalinization,silicification,potassic alteration,pyritization,sericitizetion,kaolinization,and chloritication action.The gold mineralization is closely related with silicification and pyritization.The oxygen isotope compositions in the fluid are mixture of magma water with meteoric water.The feature of sulfur isotope shows multiple origins of sulfur in mineralization fluid,mainly from volcanic-intrusive complex and the basement strata.It is assumpted from lead isotope characters that lead is mainly origin from Mesozoic volcanic rocks and partly from basement rocks.It is therefore believed that the ore forming matter of the deposit is mainly origin from magma of the mantle and partly from the strata.The temperature for mineralization is between 215～260℃.The deposit belongs to middle-lower temperature post-subvolcanic hydrothermal gold deposit.