短波红外光谱技术在矽卡岩型矿床中的应用——以鄂东南铜绿山铜铁金矿床为例

摘要

铜绿山铜铁金矿床是长江中下游铜铁多金属成矿带最重要的矽卡岩型矿床之一,矿床的形成与铜绿山石英闪长岩株体密切相关,矿体主要沿北北东向断裂产于石英闪长岩与大理岩/白云质大理岩的接触带,形成钙-镁复合型矽卡岩铜多金属矿化.围岩蚀变由致矿岩体到接触-蚀变矿化中心为:绢云母-绿泥石-钾化带、高岭石-绿泥石-弱矽卡岩化带、皂石-绿泥石-强矽卡岩化带.蚀变矿化期次可分为岩浆-热液期和表生期,其中,岩浆-热液期可分为矽卡岩阶段、退化蚀变阶段、氧化物阶段、硫化物阶段和碳酸盐阶段.绿泥石是钻孔岩芯中出现最多且分布最为广泛的蚀变矿物之一.经短波红外光谱(SWIR)研究发现,从蚀变矿化中心到外围,绿泥石出现由铁绿泥石/铁镁绿泥石逐渐转变为镁绿泥石,且绿泥石Fe-OH特征吸收峰位值(Pos2250)显示出从高值变为低值的趋势.结合其他蚀变矿物的空间分布特征,文章提出绿泥石的高Fe-OH特征吸收峰位值(Pos2250＞ 2253 nm)与金云母、蛇纹石、绿帘石、皂石和高岭石的大量出现,对指示铜绿山矽卡岩型矿床的矿化中心具有一定的作用.%The Tonglvshan Cu-Fe-Au deposit,associated with the Early Cretaceous Tonglvshan quartz diorite stock,is one of the most important skarn deposits in the Middle-Lower Yangtze River metallogenic belt.The Cu-polymetallic mineralization with Ca-Mg compound skarn alteration mainly occurs in the contact zone between quartz diorite and marble/dolomitic marble.From the quartz diorite pluton to the hydrothermal mineralization center,the Tonglvshan deposit generally exhibits sericite-chlorite-potassic alteration,kaolinite-chlorite-weak skarn alteration,and saponite-chlorite-strong skarn alteration.The hypogene alteration and mineralization at the Tonglvshan deposit can be divided into skarn alteration,retrograde alteration,oxide,sulfide and carbonate stages.Chlorite is one of the most widespread minerals in this deposit.Short Wavelength Infrared (SWIR) research on Tonglvshan reveals that the chlorite transformed from Fechlorite/Intchlorite to Mgchlorite,and the values of chlorite 2250 nm absorption peak (Pos2250) show strong decreasing trend from high to low values from the mineralization center to the distal barren area.Combined with the spatial features of other minerals,the SWIR anomalous (Pos2250 ＞2253 nm) of chlorite and quantities of phlogopite,serpentine,epidote,saponite and kaolinite can be used to a certain extent to detect the mineralized skarn orebodies at the Tonglvshan skarn deposit.