Studies Of Cu-Ni Sulfide Mineralization In The Huangshandong Mafic-ultramafic Intrusion, Hami, Xinjiang

Studies of Cu-Ni sulfide deposits associated with mafic-ultramafic intrusions may improve our understanding of petrogenesis and oregenesis during basaltic magmatism. About 20 Cu-Ni sulfide mineralired intrusions have been discovered in northern Xinjiang, China.Among these sulfide mineraliration is most significant is the Huangshandong intrusion and is thus selected as a case study for this thesis.This study investigates the characteristics of mineralogy,petrology and geochemistry of the Huangshandong intrusion and the sulfide ores in the intrusion.The results are sumerrized below.Ultramafic rocks from the Huangshandong intrusion have relatively low SiO₂ and Al₂O₃,and hige MgO contents.Mafic rocks from the intrusion show a higher SiO₂ and Al₂O₃,and lower MgO contents.The intrusive rocks are characterized by enrichments in large ion lithophile elements,depletions in high field strength elements,enrichments in LREE.These characteristics are consistent with the interpretation that the parental magma of the intrusion is of tholeitic basaltic composition.Huangshandong intrusion much younger age of(U-Pb Zircon 269Ma Zhou et al.,2004)the calc-alkaline granite(Sm-Nd 361±8Ma Rui Zongyao et al.,2002)in the region suggest that the basaltic magmatism took place after the TianShan Orogenyâ…¡.Sulfide saturation is probably related to contamination with Si-rich crust plus olivine crystallization in the staging magma chamber.The parental olivine-and sulfide-charged magmas were emplaced in the Huangshandong chamber repeatedly to form the multiphase intrusion.Gravitational setting of immiscible sulfide droplets after magma emplacement form the ore bodies in the base of the ultramafic units.