Cr-PGE mineralizations and Os-isotope signatures of chromitites in the Kahramanmaras ophiolitic complex, Southeastern Turkey

More than 2000 deposits of podiform-type chromitites are known in Turkey; thereby this country can be grouped among the world's richest areas for the chromium recovery. Podiform-type chromitites have been recognized as a potential source for platinum-group elements (PGE) recovery. Despite of this great economic interest, few data are available in literature concerning the chromite composition, as well as PGE mineralogy and geochemistry of Turkish chromitites (Uysal et al. 2005, 2006). In this abstract we present the results of a mineralogical and geochemical investigation of the Kahramanmaras chromitites, located in southeastern Turkey. As the majority of the other Turkish chromitites, the Kahramanmaras chromitites are hosted in the mantle sequence of Cretaceous ophiolitic complexes that are considered the remnants of the Tethyan Ocean. According to the last geodynamic interpretations, all the Turkish ophiolites formed in supra-subduction zone (SSZ) setting (Parlak et al. 1996, 2002; Uysal et al. 2005, 2006). The Kahramanmaras chromitites form small deposits and display massive, nodular, disseminated and rarely banded textures. The chromitite bodies are always surrounded by dunite envelopes in mantle tectonite. They are chromium-rich (Cr sub(2)O sub(3) up to 60.01 wt%) and have low titanium content (TiO sub(2) less than 0.18 wt%). Their total PGE content is low and varies from 28 to 541 ppb. They display an enrichment in Ru+Os+Ir over Rh+Pt+Pd and, as consequence, a negative slope of the chondrite-normalized patterns, although some chromitites are slightly enriched in Pt. Consistent with these geochemical data, several Ru-Os-Ir minerals have been found in the Kahramanmaras chromitites (laurite, iridium, irarsite) accompanied by minor hollingwor-thite and unidentified Ir-Pt-Rh-Fe-Cu sulfides. The Platinum group minerals (PGM) are very small in size (generally less than 10 microns) and they occur as single or polyphasic grains, in association with clinopyroxene, amphibole, base metals sulfides and other PGM. They are located in fresh chromite, along cracks of chromite filled with chlorite and in the matrix of serpentine. Despite of their association with altered silicates, on the basis of their composition, shape and chemical zoning, most of the Kahramanmaras PGMs are considered to have formed at high temperature, prior or concomitantly with the crystallization of the host chromite. The super(187)Os/ super(188)Os isotopic composition of the chromitite sample