江西省广昌县竹坑铜银矿床地质特征及矿床成因分析

江西省广昌县竹坑铜银矿床位于华南板块南华造山带武夷隆起区中段,江西省广昌县和福建省建宁县交界处。本次研究从矿床地质特征入手,对矿床不同类型矿石的黄铜矿、黄铁矿、闪锌矿所含元素含量用电子探针进行测定,分析不同类型矿石的黄铜矿、黄铁矿、闪锌矿的地球化学特征,从而推断竹坑矿床成因。研究表明矿体赋矿围岩主要有震旦系下统上施组混合花岗岩;矿体赋存于北东向F4断裂构造内,均受北北东向、北西向断裂构造共同制约;铜银矿体形态较简单,呈脉状、似层状、船状产出;竹坑铜银矿化与碳酸盐化、硅化、黄铁矿化蚀变紧密相关。矿石中黄铁矿Fe/S平均值0.82~0.83,小于0.875,Co/Ni比值1.26~53;显示出热液成因特点。矿石中黄铜矿平均成分的矿物化学式为Cu 0.933 Fe 0.971 S 2,显示竹坑矿床中黄铜矿普遍富硫的特点;矿石中闪锌矿呈红褐色,闪锌矿中Fe含量为8.466%~10.748%,平均值为9.334%,含量明显偏高;从而表明了矿床黄铜矿形成于中低温环境。综上现象推断广昌县竹坑铜银矿床属中低温热液型矿床。

Geological characteristics and genesis of the Zhukeng copper-silver deposit in Guangchang County, Jiangxi Provine

The Zhukeng copper-silver deposit of Guangchang county, Jiangxi province adjoining Jiannjng county of Fujian Province, is located in the middle section of the Wuyi uplift in the south China orogenic belt of the South China plate. Based on the geological characteristics of the deposit, this study measured the content of chalcopyrite, pyrite and sphalerite in different types of ores using electronic probes, analyzed their geochemical characteristics, inferred the genesis of the deposit. The research shows that the ore body-hosting surrounding rock is mixed granite in the Shangshi Formation of lower Sinian System. The ore bodies are located in the northeast-oriented F4 fault, jointly restricted by the north-north-east and north-west-oriented fault structures. Copper and silver orebodies have relatively simple shapes, with vein-like, layer-like, and boat-like occurrence. Copper-silver mineralization is closely related to carbonate, silicidation, and pyrite alteration. The average Fe/S of pyrite in the ore is 0.78-0.89 less than 0.875, and the Co/ Ni ratio is 1.26-53, showing a feature of hydrothermal genesis. The mineral chemical formula of the average composition of chalcopyrite in the ore is Cu0.933Fe0.971S2, implying that the chalcopyrite in the Zhukeng deposit is generally sulfur-rich. The sphalerite in the ore is reddish brown, and the Fe content in the sphalerite is 8.466%- 10.748%, with an average value of 9.334%, obviously high.This indicates that the chalcopyrite formed in a medium-low temperature environment. To sum up, it can be concluded that the Zhukeng copper-silver deposit in Guangchang county is a low-temperature hydrothermal deposit.