Sulfide petrology of basalts at DSDP Holes 69-504B and 69-505B

Primary sulfides form both globules, consisting of quenched single-phase solid solutions, and irregular polymineralic segregations of pyrrhotite, chalcopyrite, cubanite, and pentlandite. Two types of sulfide solid solutions - iron-nickel (Mss) and iron-copper (Iss) - were found among sulfide globules.

These types appear to have formed because of sulfide-sulfide liquid immiscibility in the host magmas; as proved by the presence of globules with a distinct phase boundary between Mss and Iss. Such two-phase globules are associated with large olivine phenocrysts. Inhomogeneties among the globule composition likewise are caused by sulfide-sulfide immiscibility.