Ophiolitic chromitites from the Kahramanmaras area, southeastern Turkey: Their platinum-group elements (PGE) geochemistry, mineralogy and Os-isotope signature


UYSAL İ. , ZACCARINI F., GARUTI G., MEISEL T., TARKIAN M., BERNHARDT H. J. , ...Daha Fazla

OFIOLITI, cilt.32, ss.151-161, 2007 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 32 Konu: 2
  • Basım Tarihi: 2007
  • Dergi Adı: OFIOLITI
  • Sayfa Sayıları: ss.151-161

Özet

Mantle-hosted podiform chromitites from ophiolites of the Kahramanmaras area (south-eastern Turkey), have been investigated with ragard to the chromite composition, Platinum-group elements (PGE) concentration and mineralogy, as well as Os-isotope geochemistry. Chromitites vary from At-rich to Cr-rich, however they indifferently display enrichment in Os-Ir-Ru over Rh-Pt-Pd, with concentrations of PGE lower than 510 ppb. Consistently, the most abundant Platinum-group minerals (PGM) are Ru-Os-Ir sulfides and alloys with subordinate Ir-Ru-Rh sulfarsenides and one grain of unidentified Pd-Sb phase. Textural relationships indicate that the PGM sulfides and alloys are mostly magmatic in origin, i.e. formed at high temperature prior to or concomitant with the crystallization of chromite, whereas the sulfarsenides and the Pd bearing minerals were formed during post-magmatic processes. The Kahramanmaras chromitites display relatively high Re/Os ratios, that coupled with error-chron calculated ages, point to a mixing of mantle-derived Os with Os from a source characterized by a relatively high radiogenic signature, possibly subduction-related fluids. If the genesis of the Kahramanmaras ophiolites is related to subduction, the concomitant presence of Al-rich and Cr-rich chromitites suggests chromite precipitation from melts varying in composition from MORB-like back-arc basalts (Al-rich chromite) to boninites (Cr-rich chromite). The geochemical and mineralogical data indicate that most of the Kahramanmaras chromitites have low PGE potential, due to low PGE concentration, small size of the PGM grains, and predominance of Ru-Os-Ir over Rh-Pt-Pd.