摘要
湖北铜绿山Cu-Au-Fe矿床是长江中下游成矿带内重要的大型矽卡岩型Cu多金属矿床,矿体主要呈透镜状及似层状产于早白垩世石英二长闪长(玢)岩与(白云质)大理岩的接触带.本次研究通过热红外光谱(TIR)分析,在铜绿山矿区内识别出矽卡岩矿物、退化蚀变矿物、碱性长石、斜长石、石英和碳酸盐类矿物等 49 种矿物.结合岩相学观察和已有的短波红外光谱(SWIR)蚀变填图,从热液矿化中心到远端将铜绿山矿区的围岩蚀变分带依次划分为:矽卡岩-热液矿化中心带(蚀变带Ⅲ)、近矽卡岩化带(蚀变带Ⅱ)、远端成矿岩体(蚀变带Ⅰ)和远端大理岩带(蚀变带Ⅳ),且在靠近矽卡岩-热液矿化中心附近,铁镁绿泥石、铁绿泥石、皂石、高岭石、矽卡岩和退化蚀变矿物显著增多.此外,对大量钻孔岩心样品进行磁化率分析,结果显示,矿区样品的磁化率变化范围较大(0～2000×10-3),且在靠近热液矿化中心区域磁化率显著增高,这主要是由于铁磁性矿物和矽卡岩矿物含量显著增高.综上,提出铁镁绿泥石、铁绿泥石、矽卡岩和退化蚀变矿物的显著增多、石榴子石Pos11400>11400 nm以及磁化率显著增大可以作为铜绿山矽卡岩型Cu-Au-Fe矿床新的找矿勘查标识.
Abstract
The Tonglushan Cu-Au-Fe deposit in Hubei province is a large important skarn ore deposit in the Middle-Lower Yangtze River Metallogenic belt,Eastern China.The ore bodies mainly occur as lenticular and stratiform-like features in the contact zone between the Early Cretaceous quartz monzodiorite and its hypabyssal porphyry and(dolomitic-)marbles.In this study,49 minerals were identified in the Tonglushan ore deposit by using Thermal Infrared(TIR)analysis,including skarn and retrograde alteration minerals,alkali feldspar,plagioclase,quartz,and carbonates.Based on the macro/microscopic textural relationships and alteration mineral mapping,the following alteration zoning were identified,i.e.,skarn-hydrothermal mineralization center(alteration zone Ⅲ),endoskarn close to the skarn(alteration zone Ⅱ),and distal quartz monzodiorite(porphyry)(alteration zone Ⅰ)or(dolomitic-)marbles(alteration zone Ⅳ)from the mineralization center outward.Moreover,the Fe-Mg chlorite,Fe-chlorite,muscovite,saponite,kaolinite,skarn and retrograde alteration minerals show a significant increase near the skarn-hydrothermal mineralization center at Tonglushan.Moreover,the magnetic susceptibility analysis shows a significantly large variation(0-2000×10-3)within the Tonglushan mining area.Due to the high contents of ferromagnetic-and skarn minerals in the hydrothermal mineralization center,the high anomalies of MS occur near the hydrothermal mineralization center.In conclusion,the presence of Fe-Mg chlorite,Fe-chlorite,skarn and retrograde alteration minerals,Pos11400>11400 nm,and an increase of magnetic susceptibility in the samples can be used as new vectors to explore the mineralization centers in the Tonglushan Cu-Au-Fe skarn deposit.
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