Genesis of giant Fe-Ti oxide deposits in the Panxi region, SW China: A review

The Panxi region, SW China, has been an important source of Fe, Ti, and V metals in the world. Several giant deposits, such as the Panzhihua, Hongge, Baima and Taihe, are hosted in ca. 260 Ma mafic-ultramafic layered intrusions in this region. These Fe-Ti oxide-bearing intrusions are unique in that they contain large proportions of massive ores in the lower and middle parts within the relatively small bodies. It is generally acknowledged that they have Fe-Ti-rich and Si-poor parental magmas that were derived from a Fe-rich mantle source containing pyroxenite/eclogite components and follow a tholeiitic differentiation trend at depth. However, it remains controversial on the mechanism of forming such large amounts of Fe-Ti oxides, with two main views of fractional crystallization and magma unmixing. Integrating previous studies, we suggest that magma unmixing has happened during the evolution of the Fe-Ti-rich magmas. Separation of immiscible Si-rich melts led to the accumulation of denser Fe-rich melt in the lower part of magma chamber. Large amounts of Fe-Ti oxides crystallized from the immiscible Fe-rich melt to form the major massive ores. The combined effects of fractional crystallization and magma unmixing can explain the enigmatic features of the Fe-Ti oxide-bearing layered intrusions in the Panxi region.