Abstract:
Objective Based on olivine major and trace element analyses of four ultramafic small intrusions in the Qixin intrusion of the Beishan Mountains in Xinjiang, this study explores the nature of the magma source area and the sulphide melting process, offering key theoretical and technical insights for ore exploration.
Methods The study using EPMA and LA−ICP−MS systematically determines the major and trace element compositions of olivine from different intrusive bodies. The ore−forming potential of different intrusive bodies is evaluated by characterizing olivine composition and reconstructing magmatic evolution processes.
Results The results show that olivine of peridotite in each intrusion has Ni losses of varying degrees(the Fo value and Ni concentration of olivine in the No. Ⅰand Ⅱ intrusion are 84.0 mol%~87.5 mol% and 134×10−6~2562×10−6, the No. Ⅲ and Ⅳ intrusion are 82.3 mol%~86.1 mol% and 581×10−6~2970×10−6), the olivine have high Mn/Zn value(>15) and 100*Mn/Fe value(1.4~1.7), and low 10000*Zn/Fe value(3.5~9.4), and medium Li concentration(1.8×10−6~9.8×10−6).
Conclusions The study indicates that mantle origin of the Qixin intrusion is a peridotite mantle in the source origin and mixed by material from continental crust during magmatic evolution. The Fo values and Ni−Co compositional trends in olivine indicate that the sulfide segregation of the deep in the intrusion No.Ⅰ and Ⅱ are more significant, and there is potential to search for Ni−Co deposit in the deep. Therefore, ore prospecting and exploration need to further focus on intrusion No.Ⅰ and Ⅱ deep exploration and evaluation.
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