Petrological characteristics and geochemical compositions of the Neotethyan Mersin ophiolite (southern Turkey): Processes of melt depletion, refertilization, chromitite formation and oceanic crust generation

The Mersin ophiolite of the Central Taurides in southern Turkey represents an incomplete section of ocean lithosphere consisting from bottom to top of chromitite-bearing mantle peridotites, cumulate dunites, clinopyroxenites, and gabbros with rare pillow lavas covered by bathypelagic sedimentary rocks. The tectonized peridotites are harzburgites with minor dunites. They are strongly melt-depleted peridotites, comprising chromian spinel (Cr-spinel) with medium to high Cr-numbers (Cr#) [100 x Cr/(Cr + Al) = 48-82] and low Al2O3 concentrations (0.05-2.2 wt%). They display concave chondrite-normalized rare earth element (REE) patterns, which we interpret as evidence for their refertilization by boninitic melts in a mantle wedge. Geochemical evidence suggests that the parental magmas of the high-Cr podiform chromitites (Cr#(sp) = 71-83) were of boninitic composition. The chromitites host a platinum-group mineral (PGM) assemblage of laurite [Ru#-64.0-90.7] and Os-Ir alloys, indicating crystallization within a range of low fS(2) conditions (logfS(2) similar to -2 to -1.3) and a T-max of similar to 1200 degrees C.