Metallogenic Conditions and Prospecting Potential of Mafic-ultramafic Rocks along Dashantou-Heishan Area in Beishan, Gansu Province

The Dahantou-Heishan area is located in northern margin of the Tarim plate, where mafic-ultramafic rocks related to mineralization are more widespread. The ore-bearing rock is more controlled by Miaomiaojing-Xishuangyingshan fracture and secondary faults, with the diagenetic age concentrated in the age of 358~397Ma. The formation and evolution of these rocks is closely related rifting. In this area, the copper-nickel mineralized mafic-ultramafic rock is small in scale, with multi-stage emplacement and good differentiation, as well as the features of high magnesium, low alkali, low calcium and low titanium. The ore-bearing facies have high Mg# values, and their REEs show relatively flat features in distribution patterns, with the slight enrichment of LREE, relative enrichment of LILE (Rb,Ba,Sr,U) and relative depletion of high field strength elements (Nb,Zr,Hf). The development degree of mineralized rock strength is not high, but large-scale copper and nickel mineralization anomalies are well developed, which can fit the magnetic and electrical abnormalities well. After carrying out the research on geological characteristics, petrological characteristics and rock geochemistry of several copper-nickel mineralized mafic-ultramafic rocks, and combining with the geological prospecting practices in recent years, it's considered that the ore-forming conditions for copper-nickel mineralization associated with ferruginous mafic-ultramafic rocks are very well, which has a potential to further search for copper-nickel magmatic deposits.