Quantitative simulation for the formation of Baimazhai Ni-Cu sulfide deposit in Yunnan Province.

Fractional crystallization and crustal contamination are important factors to trigger magma over S-saturation. In this study, we chose the Permian low-Ti picrite in Jinping-Song Da area as a primary magma to simulate fractional crystallization and crustal contamination which may trigger the magma over S-saturation to form Baimazhai Ni-Cu sulfide deposit based on MELTS program. The simulation shows that 10% olivine had crystallized from the low-Ti picritic magma and then the residue magma would become to high-Mg basaltic. In the upper crust chamber, the high-Mg basaltic magma had contaminated more than 18% wall rocks and 27% silicate minerals have crystallized, then the magma would reach S-saturation. The segregated sulfide was concentrated to middle of magma channel by flow differentiation, and consequently, formed Baimazhai concentric Ni-Cu sulfide deposit. The magma which underwent sulfide segregation erupted to form the Ni- and Cu-depleted low-Ti basalt with significant crustal contamination characters in Jinping-Song Da area.