Title Two stages of immiscible liquid separation in the formation ofPanzhihua-type Fe-TiV oxide deposits

Magmatic oxide deposits in the w260 Ma Emeishan Large Igneous Province (ELIP), SW China and northern Vietnam, are important sources of Fe, Ti and V. Some giant magmatic Fe-Ti-V oxide deposits, such as the Panzhihua, Hongge, and Baima deposits, are well described in the literature and are hosted in layered mafic-ultramafic intrusions in the Panxi region, the central ELIP. The same type of ELIPrelated deposits also occur far to the south and include the Anyi deposit, about 130 km south of Panzhihua, and the Mianhuadi deposit in the Red River fault zone. The Anyi deposit is relatively small but is similarly hosted in a layered mafic intrusion. The Mianhuadi deposit has a zircon U-Pb age of w260 Ma and is thus contemporaneous with the ELIP. This deposit was variably metamorphosed during the Indosinian orogeny and Red River faulting. Compositionally, magnetite of the Mianhuadi deposit contains smaller amounts of Ti and V than that of the other deposits, possibly attributable to the later metamorphism. The distribution of the oxide ore deposits is not related to the domal structure of the ELIP. One major feature of all the oxide deposits in the ELIP is the spatial association of oxide-bearing gabbroic intrusions, syenitic plutons and high-Ti flood basalts. Thus, we propose that magmas from a mantle plume were emplaced into a shallow magma chamber where they were evolved into a field of liquid immiscibility to form two silicate liquids, one with an extremely Fe-Tirich gabbroic composition and the other syenitic. An immiscible Fe-Ti-(P) oxide melt may then separate from the mafic magmas to form oxide deposits. The parental magmas from which these deposits formed were likely Fe-Ti-rich picritic in composition and were derived from enriched asthenospheric mantle at a greater depth than the magmas that produced sulfide-bearing intrusions