Mineralogical characteristics of the meta-mafic-ultra?mafic intrusive rocks on the southern margin of Fenghuangling, southern Shaanxi: An indicator of Fe- Ti metallogenesis

The meta-mafic-ultramafic intrusive rocks in southern Fenghuangling are ore-bearing rocks with abundant useful elements such as Fe and Ti. In this study, geochemical method, polarizing light microscope and electron probe micro analysis (EPMA) were conducted to investigate the petrologic, geochemical and mineralogical characteristics of the meta-maficultramafic intrusive rocks. The Fe - Ti oxide formation and enrichment were also studied so as to probe into diagenesis and mineralization. The results show that, in this area, ore-bearing meta-mafic-ultramafic intrusive rocks and barren meta-mafic-ultramafic intrusive rocks resulted from simultaneous magmatism of different magma source areas, and the Fe-Ti mineralization of meta-mafic-ultramafic intrusive rocks had a close relationship with the initial magma source rocks. Fe-Ti oxides mostly exist in sphene and ilmenite but sometimes it also exists in a small amount of rutile. Ilmenite is rich in MnO but poor in MgO. The formation and enrichment process of Fe-Ti oxide experienced the stages of magma crystallization differentiation and hydrothermal alteration.