Petrogenesis of ophiolitic chromitites from the Southeastern Turkey: Chromite composition and geochemistry and mineralogy of platinum group elements

Ophiolitic chromitites from southeastern Turkey are located within the mainly mantle peridotites (harzburgite and dunite) in the form of veinlets and lenticular bodies. Chromitites show a wide variation of Cr composition (Cr# = 39?82), range between 42 and 348 ppb (mean 135 ppb) in total PGE concentrations. High?Cr chromitites (Cr# > 70; Mg# = 45.3?67) mainly contain low TiO2 (?0.2 %wt.) and higher total PGE contents (mean 158 ppb), whereas low?Cr ones (Cr# < 70; Mg# = 57.2?75.2) contain higher TiO2 contents (0.2?0.4 %wt.) and represented lower total PGE contents (84 ppb) slightly. However, one sample in high?Cr composition show a significant enrichment in PGE up 2.7 ppm. PGM and BMM mineralogy suggests that chromites crystallized high temperature (1300oC?1000oC) and low ?S2 (?4) conditions. Chemical, mineralogical, trace element, calculated primitive melts composition in southeastern Turkey ophiolitic chromitites and also textural, mineralogical features of primary inclusions indicate that the high?Cr chromitites are crystallized out of boninitic melt in a subduction environment, whereas chromitites of high?Al composition are thought to crystallized either from the MORB type melt in mid oceanic ridge setting or back?arc environment.