The Guleman ophiolitic chromitites (SE Turkey) and their link to a compositionally evolving mantle source during subduction initiation


UYSAL İ. , Kapsiotis A., Akmaz R. M. , Saka S. , SEITZ H. M.

ORE GEOLOGY REVIEWS, vol.93, pp.98-113, 2018 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 93
  • Publication Date: 2018
  • Doi Number: 10.1016/j.oregeorev.2017.12.017
  • Title of Journal : ORE GEOLOGY REVIEWS
  • Page Numbers: pp.98-113
  • Keywords: Chromian spinel, Trace elements, Platinum-group elements, Ophiolite, Guleman, PLATINUM-GROUP MINERALS, CHROMIAN SPINEL COMPOSITION, EASTERN BUSHVELD COMPLEX, GROUP ELEMENT MINERALOGY, MELT-ROCK INTERACTION, PODIFORM CHROMITITES, OMAN OPHIOLITE, SOLID INCLUSIONS, TRACE-ELEMENTS, SW TURKEY

Abstract

Economically viable chrome ore bodies are hosted within a unit of pervasively serpentinized harzburgite in the Guleman mine of the homonymous ophiolite in SE Turkey. Chrome ores consist of m- to tens of m-scale tectonically imprinted chromitite bodies, showing semi-massive to massive texture and podiform to lenticular morphology. They are hosted in dunite envelopes of variable thickness and are composed of chromian spinel [Cr-spinel] with high Cr#[Cr/(Cr + Al) = 0.61-0.81] and Mg# [(Mg/Mg + Fe2+) = 0.56-0.72], and low TiO2 (0.06-0.33 wt%) content. Compositionally, they are divided into intermediate-Cr (CrSp#: 0.610.69) and high-Cr chromitites (Cr#Sp: 0.71-0.81). Chromian spinel from the intermediate-Cr chromitites is richer in Ni, Ti, Zn and Ga compared to that from the high-Cr chromitites. Both chromitite types show a general enrichment in IPGE (Os, Ir and Ru) over PPGE (Rh, Pt and Pd). The PGM assemblages of these chromitites are dominated by small (<= 6 mu m), idiomorphic inclusions of Ru-Os bisulfides and subordinate Os-Ir-Ru alloy in Cr-spinel. Bisulfides within the intermediate-Cr chromitites show a wider range of Os-for-Ru substitution than those hosted in the Cr-rich chromitites [Ru/(Ru + Os): 0.15-0.86 vs. 0.71-0.86, respectively].