东天山镁铁质_超镁铁质岩带岩石特征及铜镍成矿作用

东天山地区分布有众多镁铁质-超镁铁质岩体,岩体成群成带状分布,从北向南可划分为7个区带,受区域性韧性剪切带和断裂构造控制。从岩相学来看,本区含矿岩体可分为多期次侵入的复式杂岩体和单期次侵入的超镁铁质单式杂岩体,显示出深源岩浆充分分异的特征。含矿岩体具有高镁、低碱、低钙、低铝、低钛特征,具有较高的Mg#、m/f和m/s比值,兼具岩浆硫化物熔离作用与岩浆结晶分异作用。根据TiO2-10P2O5-10MnO图判别出本区岩浆具有拉斑玄武岩到钙碱玄武岩过渡的性质,岩浆源具有钙碱性玄武岩浆特征,富含含水矿物,预示了早期俯冲洋壳对幔源岩浆的交代作用。岩体矿化分为3种成矿作用和5期成矿步骤,且岩浆成矿作用与热液作用几乎同时进行,岩浆分异作用提供热液来源,而热液作用促进硫化物的饱和与熔离,造成岩石的热液蚀变结构并对岩浆期成矿进行改造。晚期岩体隆升后,矿体出露地表遭受氧化淋滤作用,形成特有的地表氧化带找矿标志。

Petrological characteristics and copper-nickel ore-forming processes of Early Permian mafic-ultramafic intrusion belts in East Tianshan

Mafic-ultramafic intrusions in East Tianshan area are reclassified into seven belts,which are distributed as clusters and belts,with the intrusions in the same belt controlled by a regional structure.In the light of petrography,the ore-bearing intrusions must have been formed by multiple intrusion or a single intrusion,indicating a perfect magmtic evolution and fractionation.With high Mg and low alkaline,Ca,Al and Ti,the ore-bearing lithofacies show high Mg# value and high m/f and m/s ratios.Sulfide segregation and magmatic fractionation took place simultaneously.With a TiO2-10P2O5-10MnO plot,the transitional nature of the primary magma from tholeiite to calc-alkaline can be identified,with most intrusions assuming the calc-alkaline trend.The intrusions of this area mostly possess hydrous minerals such as hornblende and biotite generated from alteration of pyroxenes,implying metasomatism of the mantle magma caused by the early subducting oceanic crust.The mineralization can be classified into three processes and five stages.The processes consisted of magmatic mieralization,hydrothermal mineralizaion,oxidation and eluviation.The five stages were successive and constituted a whole process,and in the middle magma chamber the sulfur reached saturation,with the magma experiencing pulsating intrusion as well as ore-rich magmatic intrusion at the final stage,loaded with hydrothermal mineralization,oxidation and eluviation.Magmatic mineralization occurred synchronously with hydrothermal mineralization,the magmatic stage could offer hydrothermal sources,and the hydrothermal process could be favorable to the sulfur saturation and sulfide segregation.The hydrothermal alteration structures and ores formed at the magmatic stage were reformed at the hydrothermal stage.During the uplift of the intrusions,ore bodies were subjected to oxidation and eluviation,resulting in a special kind of oxiding alteration which can serve as indicators for prospecting in depth.