Platinum-Group Minerals (PGM) and Other Solid Inclusions in the Elbistan-Kahramanmaras Mantle-hosted Ophiolitic Chromitites, South-eastern Turkey: Their Petrogenetic Significance

The Elbistan-Kahramanmaras podiform ophiolitic chromitites, in southeastern Turkey, contain abundant primary inclusions of platinum-group minerals (PGM), base-metals sulphides (BMS) and silicates. These inclusions are very small, generally less than 15 microns in size, and mostly occur in chromian spinel. The following PGM have been recognized: laurite, iridium, irarsite, ruarsite and several unidentified PGE phases. Millerite, pentlandite, bornite, digenite, chalcopyrite and betekhtinite are the BMS that have been identified. Mg-rich hornblende, accompanied by rare olivine, clinopyroxene and phlogopite, are the most abundant silicate inclusions. Most of the PGM, BMS and silicate inclusions are considered primary, i.e. formed during the high temperature magmatic stage. Based on textural relations, paragenesis and composition, it was established that osmium-bearing alloys crystallized before than Ru-rich laurite and millerite at temperatures between 1300 and 1000 C. These observations are consistent with the experimental results. Few PGM were altered after magmatic crystallization indicating that serpentinization and weathering processes that affected the complex were not strong enough to produce secondary PGM. The presence of abundant hydrous primary silicate inclusions in mostly high-Cr and low-Ti chromian spinel suggests that the Kahramanmaras chromitites crystallized from the melt, itself formed as a result of various degrees of partial melting of the upper mantle, under a fluid activity, in a subduction zone geodynamic setting.