粤东麻坑非硫化物型锌矿锌的赋存状态及成因讨论

Zinc Occurrence and Genesis of the Makeng Nonsulfide Zinc Deposit in the Eastern Guangdong Province

麻坑锌矿位于粤东晚古生代梅州拗陷东北部、近南北向蕉岭向斜的西翼,含矿岩石为强风化浅绿色粘土岩、黑色锰土及黑土角砾岩,未见原生金属硫化物,因此,有关锌的赋存状态及矿床成因一直不明。本文通过系统的岩矿石样品光薄片、砂光片显微镜下鉴定、X射线粉晶衍射物相分析和电子探针成分分析,查明了锌矿物主要以异极矿形式存在,仅含极少量菱锌矿;本矿床氧化作用较为彻底,矿床成因属浅成非硫化物型锌矿的直接交代亚类。上述锌的赋存状态及矿床成因探讨对类似矿床的认识与勘查具重要意义。

Makeng zinc deposit, located in the eastern part of Guangdong, is tectonically situated on the west flank of the nearly north-south Jiaoling syneline in the northeastern area of the late Mesozoic Meizhou depression of in eastern Guangdong Province. The ore-bearing rock was strong weathered to reseda clay rock, black rnanganomelene and black soil breccia, and no original metal sulfides is visible. Therefore, the occurrence of zinc and genesis of deposit has long been no clear. Based on study on thin and polished sections, mineral X-ray powder diffraction and electronic microprobe, the zinc minerals mainly occurs as hemimorphite and minor smithsonite. This suggests that ore body has experienced intense oxidation, and the deposit belongs to direct replacement subtype （supergene nonsulfide zinc deposits）. Therefore, this study is of great significance for exploration of similar deposits.