Mineral chemistry of ore-bearing ultramafic rocks from the Hongqiling Nos.1 and 7 instrusions in Jilin Province: Constraints on the magmatic processes and the metallogenesis of Ni-Cu sulfide deposits
吉林红旗岭1号和7号岩体中含矿超镁铁质岩的矿物化学特征:对岩浆演化过程以及铜镍硫化物矿床形成机制的约束

Systematic studies on the mineralogy of the ore-bearing ultramafic rocks from the Hongqiling Nos.1 and 7 intrusions in east Jilin Province show that the rocks mainly consist of chrysolite,bronzite,clinopyroxene,plagioclase,hornblende and phlogopite. These minerals were crystallized from magma at different depths.In particular,olivine and pyroxene are the best rock-forming minerals that crystallized firstly from the primary magma and could be used to trace the magma,which were derived from the upper mantle.The parental magmas of these intrusions in the intermediate magma chamber are hydrated high-Mg picritic basalt magma and the MgO content were estimated to be about 1 3.98%and 1 4.22%with Mg # of 72.22 and 71.05 respectively.The depth of the deep-level magma chamber,where only olivine and pyroxene fractional crystallization processes took place ephemerally,was estimated to be about 26～27 km.The temperature of magma chamber was 1 280～1 379℃.When magma uplifted from the deep-level to the high-level chamber,this process was nearly adiabatic and completed in a short time.Then,magma maybe experienced double chamber evolutions.Meanwhile,olivine and less pyroxene fractional crystallizations were over before the uplift of magma.But,there was complex process in high-level magma chamber,where crust contamination,mixing with affinal magma and super cooling have been happened.These processes contribute to the increase of ore-forming elements and the saturation of sulfide in the magmatic system,thus Ni-Cu mineralization occurs in the intrusions.