安徽贵池铜山矽卡岩型铜矿床蚀变矿化分带特征及其成因

Alteration and mineralization zoning in Tongshan skarn-type copper depositin in Guichi,Anhui Province,and its genesis

铜山矽卡岩型铜矿床产于长江中下游铁铜成矿带中的安庆—贵池矿集区。研究区矽卡岩化与矿化发生于碳酸盐岩地层与花岗闪长斑岩间的接触带中,蚀变及矿化具有水平与垂向分带特征。水平方向上,靠近岩体的矽卡岩中石榴子石含量较高,远离岩体的矽卡岩中透辉石含量较高;靠近大理岩带发育钙铁辉石矽卡岩,远离大理岩带的灰岩硅化较强。垂向上,从上到下依次为角岩带、钙质矽卡岩带和镁质矽卡岩带。矿物成分研究表明,靠近岩体处氧化性较强,石榴子石的钙铁榴石端员含量高;铜多富集于含石英脉的岩体、距岩体略远的矽卡岩、角岩或大理岩中,而锌多富集于硅化灰岩及远离岩体的矽卡岩中。研究表明,该矿床中蚀变矿化经历了进变期和退变期,包括接触热变质阶段、进化交代阶段和早退化蚀变阶段、晚退化蚀变阶段。其中,大规模的黄铜矿化主要发生于早退化蚀变阶段,且在岩浆演化晚期进一步富集于斑岩石英脉中。

The Tongshan skarn-type copper deposit is located in the Anqing-Guichi ore concentration area along the lower and middle Yangtze River reaches iron-copper metallogenic belt.In the study area,skarnization and min-eralization occur in the contact zone between carbonate and granodiorite porphyry.Alteration and mineralization show significant horizontal and vertical zoning characteristics.In horizontal zoning,the garnet content of skarns near the pluton is high,the diopside content of skarns far from the pluton is high,and the hedenbergite content of skarns near the marble is also high.The limestone far away from the marble experienced strong silicification.In vertical zoning,hornfels,calcareous skarn and magnesian skarn occur in downward succession.Mineralogical studies show that the skarn zone near the pluton has been relatively strongly oxidized and the garnet in it has relatively high And（andradite end-member）.Cu is concentrated in such bodies as porphyries with quartz veins,skarns a bit far from the pluton,and hornfels or marbles,while Zn is usually abundant in silicified limestones and skarns far from the pluton.Studies suggest that the alteration and mineralization of the Tongshan ore deposit experienced the prograde period and the retrograde period.The former period could be divided into the contact metamorphic stage and the prograde metasomatic stage,and the latter into the early retrograde stage and the late retrograde stage.Copper mineralization mainly took place at the early retrograde stage,and was further concentrated in quartz veins of the porphyries during the late stage of magmatic evolution.