Percolation of sulfide liquid through semi-consolidated silicate cumulates: Textural evidence from breccia ores in the Kalatongke Cu-Ni sulfide deposit, NW China

Abstract

The Kalatongke Cu-Ni sulfide deposit is an important Ni producer in China and contains abundant breccia ores which are especial in that the silicate fragments enclosed within the sulfide matrix have similar mineral assemblages to the host norite body. Using a combination of microbeam X-ray fluorescence (μ-XRF) and Tescan integrated mineral analyzer (TIMA) mapping, and 3D morphology by high-resolution X-ray computed tomography (HRXCT), we show that the breccia ores are of magmatic origin, as there are no foliation and fabrics of silicate fragments in the sulfide matrix. The 3D morphology of the breccia ores reveal that large silicate fragments are continually connected, whereas small silicate fragments are sub-spheric to spheric with sphericity values close to 1 and commonly rimed by magnetite. All these textures can be explained by that semi-consolidated silicate cumulates were percolated by sulfide liquid from replenished sulfide-bearing magma pulse in the magma conduits. The sulfide liquid from the replenished magma may have accumulated to form a sulfide pool overlying the semi-consolidated cumulates. Due to its high density, the sulfide liquid in the pool could percolate downward and infill the fracture network in the semi-consolidated cumulates, forming sulfide networks in the breccia ores. The sulfide liquid may also trap the interstitial, silicate melts on its way downward throughout the semi-consolidated cumulates, forming small sub-spheric to spheric silicate fragments in the breccia ores. Such a process revealed by the texture of breccia ores indicates that replenished magma pulses and degrees of percolation of sulfide liquid through semi-consolidated cumulates essentially control the distribution of ore bodies in the Kalatongke deposit.