Mineral chemistry of Fe-Ti oxides in the Permian Panzhihua gabbroic intrusion, SW China: implications for the ore genesis

Abstract

Massive concentrations of Fe-Ti oxide minerals occur as lenticular, sill or dykelike b~odies in the Permian Panzhihua intrusion, SW China. Although the intrusion is characterized by well-developed igneous layering, major oxide orebodies are intimately associated with vari-textured gabbro devoid of layered structure. Magnetites in one of the major orebody at different stratigraphic heights have similar compositions and do not show evidence of fractional crystallization. Oxides in these orebodies are suggested to have crystallized from an oxide liquid, which is also consistent with field and petrographic observation. The oxide liquid might be separated immiscibly from a crystallizing gabbroic magma. The cause of oxide immiscibility cannot be evaluated with available information but abrupt change in oxygen fugacity andlor introduction of volatiles induced by assimilation of carbo~iate rocks might be potential triggering mechanisms.