河南省罗山县金城金矿黄铁矿标型特征及其意义

Typomorphic features and exploration significance of pyrite from the Jincheng gold deposit in Luoshan,Henan Province

通过对河南罗山县金城金矿Ⅱ号矿体黄铁矿产出特征、金在黄铁矿中的赋存状态、化学成分、热电性等一系列标型特征的研究,认为本区含金黄铁矿主要为热液成因。黄铁矿中硫同位素具有变化范围窄（2.75‰-5.5‰）、极差值小（2.75‰）、平均值为4.195‰的特点,表明硫主要来源于深源岩浆。热电性测试显示,黄铁矿的热电系数（α）变化范围较大（-281.0-466.0μV/℃）,平均为-148.9-268.2μV/℃,热电场导电类型N型、P-N型、N-P型及P型均有,总体上具有N-P混合型特征,同一世代黄铁矿热电性在空间上具有正向垂直分带的规律,表明本矿区的黄铁矿成分复杂,具有受多期次热液叠加的特征。黄铁矿热电性数据统计直方图明显出现两个峰值,表明本矿床至少具有两次金成矿作用阶段。通过经验公式计算预测该矿体的剥蚀深度为矿体中部位置,深部尚有较大的找矿潜力。这一研究反映了黄铁矿的标型特征对进一步扩大矿床规模和找矿具有重要的指示意义。

Pyrite is the major gold-bearing mineral in the Jincheng gold deposit. According to the comprehensive identification under microscope,the formation characteristics and mineralogical characteristics,the pyrite from the No.Ⅱ ore body can be divided into three generations.Gold mainly occurs in the first and second generation of pyrite.Chemical composition,thermal nature and mode of occurrence of gold in pyrite from the No.Ⅱ ore body show that pyrite was derived from magmatic hydrothermal source.Sulfur isotopes of pyrite have a narrow variation range（2.75‰～5.5‰）with an average of 4.195‰,suggesting that sulfur came mainly from the magmatic source.Thermal test of pyrite shows that thermal coefficient（α） has a large variation（-281.0～466.0 μV/℃） with an average of-148.9～268.2 μV/℃,and thermal conductivity type has mixed characteristics of N-type,P-N type,N-P type and P-type.The thermal characteristics of pyrite of the same generation has a positive vertical zoning trend in space,indicating that the composition of pyrite in this ore deposit is complex,suggesting the features of the superposition of multi-stage hydrothermal solutions.Thermal characteristics of pyrite show clearly two peaks in the histogram,indicating that there are at least two gold mineralization stages.The study of the erosion depth of the ore bodies in central location suggests that there still exists good prospect for concealed gold ore bodies.Typomorphic features of the pyrite can provide an important indication for further expanding gold reserves and search for ore deposits of the same type.