Co-rich sulfides in mantle peridotites from Penghu Islands, Taiwan : footprints of Proterozoic mantle plumes under the Cathaysia Block

Abundant primary sulfides occur as inclusions in silicates and as discrete grains in mantle-derived spinel lherzolite xenoliths from Miocene intraplate basalts on the Penghu Islands, Taiwan, which is located at the southeastern margin of Cathaysia Block. These sulfides are dominantly mixtures of Fe-rich and Ni-rich monosulfide solid solutions (MSS), with minor pentlandite, millerite and chalcopyrite, and are considered to represent sulfide melts crystallized at high temperatures (>900 °C). Some sulfides from the Tungchiyu (TCY) islet (37 out of 118 grains) have remarkably high Co contents resulting in subchondritic Ni/Co ratios (