Geochemical Characteristics and Genesis of the Anyi Mafic-Ultramafic Intrusion, Mouding, Yunnan Province, China

Magmatic deposits associated with mafic-ultramafic intrusions, including sulfide and oxide deposits, play a crucial role in hosting Ni-Cu-PGE-Fe-V-Ti mineral resource. Numerous such intrusions within the Emeishan Large Igneous Province (ELIP) are known for their significant Ni-Cu-PGE-Fe-V-Ti minerals. The Anyi intrusion, located in the central zone of ELIP, 840 m in length and 400 m in width of the outcrop, mainly composed (~80%) of plagioclase-bearing clinopyroxenite and titanomagnetite-bearing clinopyroxenite, hosting over 364 Mt of iron ore and ~39, 000 kg of platinum group element (Pt + Pd), with average grades of ~30 wt.% Fe₂O₃ and 0.35 g/t PGE, along with variable amounts of V₂O₅ and TiO₂. In this paper, we present data on the major and trace elements and Sr-Nd isotope geochemical characteristics of the Anyi intrusion. These data showing the light rare earth elements (LREE) enrichment and heavy rare earth elements (HREE) depleted, similar with the Emeishan basalts. The ε_Nd (t=260 Ma) of titanomagnetite-bearing clinopyroxenite and plagioclase-bearing clinopyroxenite in Anyi intrusion from −13.17 to −11.30, and the value of initial (⁸⁷Sr/⁸⁶Sr) is between 0.708496 and 0.709269, showing an enrichment feature, which share the same magma evolution trend with the Emeishan high-Ti and low-Ti basalts and peridotites, and locating in the mafic end member of the basaltic magma evolution series. The geochemical characteristics and simulation calculations of the samples indicate that the parental magma of the Anyi intrusion comes from the partial melting of deep mantle source, with the addition of recycled crustal materials in the mantle source. The parental magma mainly experienced the fractional crystallization of clinopyroxene, plagioclase, and Fe-Ti oxides, and underwent a low degree of crustal contamination during its ascent and emplacement.