Spinel compositions of mantle-hosted chromitite from the Eastern Anatolian ophiolite body, Turkey: Implications for deep and shallow magmatic processes

The Eastern Anatolian Accretionary Complex includes several ophiolitic megablocks and/or tectonic slivers within a 150-180 km long east-west trending complex formed during the Late Cretaceous-Tertiary in Eastern Turkey. The Alabayir, Mollatopuz, Yukanbalcikli and Mehmetalan ophiolites are megablocks or tectonic slivers containing locally massive, nodular or schlieren banded chromitite layers. These podiform chromitites formed in mantle sequences and are classified as high-Cr chromitites (Cr# 0.63-0.88; Mg# 0.50-0.64; 0.01-0.5 wt.% TiO2; 5.7-18.8 wt.% Al2O3). Calculated parental melt compositions of these chromitites indicate boninite magma characteristics (8.2-13.4 wt.% Al2O3; 0.64-1.50 FeO/MgO). The PGE patterns also support the view that they crystallized from a boninitic melt. The total PGE contents of chromitites vary between 79 and 390 ppb. Pd/Ir ratios of chromitites vary from 0.07 to 0.28 and are consistent with an IPGE fractionated nature.