安徽铜陵桂花冲斑岩铜矿围岩蚀变与矿化作用

Alteration and Mineralization of the Guihuachong Porphyry Copper Deposit,Tongling Area,Anhui Province

桂花冲铜矿为安徽铜陵地区新发现的斑岩型铜矿,斑岩体为准铝质高钾钙碱性的花岗闪长斑岩。围岩蚀变与矿化作用是斑岩型矿床成矿过程研究的一项重要内容,对蚀变带岩石开展元素地球化学成分的迁移研究,是分析热液交代蚀变过程的基础。桂花冲铜矿区内围岩蚀变作用比较强烈,蚀变类型主要有钾化、绢云母化、硅化、绿泥石化和碳酸盐化等。蚀变分带比较明显,由内向外依次为钾化带、绢英岩化带和青磐岩化带,矿体主要产于绢英岩化带内。矿化蚀变自早至晚划分为钾长石、石英-绢云母、石英多金属硫化物和碳酸盐4个阶段。蚀变带物质组分迁移结果表明,在蚀变过程中,岩石的主量元素除TiO2、MnO、MgO外,其他元素迁移量发生了明显改变;微量元素除Sr和Cu外,迁移量变化较小,稀土元素在矿化强的部位亏损,在矿化弱的地带富集。岩体及蚀变带岩石稀土元素球粒陨石标准化配分模式一致,说明岩体与蚀变岩石经历了相同来源流体的交代蚀变,是岩浆流体连续作用的结果。

Guihuachong copper deposit is a porphyry copper deposit newly discovered in the Tongling area,Anhui Province. Lithology of host intrusion is granodiorite porphyry,belonging to metaluminous high potassium calc-alkali granite. Wall rock alteration and mineralization study is an important porphyry deposit mineralization study on migration conducted alteration zone rock for geochemical composition of elements,which is based on the analysis of hydrothermal alteration processes. Wall rock alteration is strong in the Guihuachong mining area,and mainly consists of potassic alteration,sericitization,silicification,chloritization,and carbonatization. Alteration zoning is obvious,occurring potassic alteration,sericitization-silicification,and argillation-propylitization belts in outward succession. Major orebodies occur in the sericitization-silicification belt. Alteration and mineralization process of the hydrothermal stage from early to late is divided into four stages,i. e.,potassic alteration,sericitization-silicification, quartz-polymetallic sulfide and carbonate stages. Mineralization took place mainly in the quartz-chalcopyrite sulfide stage. The results of migration quality of components in different alteration zones showed that variation of migration quality in the alteration process is high for the major elements except TiO2,MnO,MgO and low for the trace elements except Cr and Cu,and rare earth elements are loss in strong mineralization area and enrichment in the zone of mineralization. low for the rare earth elements. The similar chondrite-normalized REE patterns of the intrusion and the altered rocks from the Guihuachong deposit show close connection of the intrusion with mineralization of the deposit and it is the result of continuous actionof magmatic fluids.