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

摘要: Abstract The Mersin ophiolite of the Central Taurides in southern Turkey represents an incomplete section ocean lithosphere consisting from bottom to top chromitite-bearing mantle peridotites, cumulate dunites, clinopyroxenites, and gabbros with rare pillow lavas covered by bathypelagic sedimentary rocks. tectonized peridotites are harzburgites minor dunites. They strongly melt-depleted comprising chromian spinel (Cr-spinel) medium high Cr-numbers (Cr#) [100 × Cr/(Cr + Al) = 48–82] low Al2O3 concentrations (0.05–2.2 wt%). display concave chondrite-normalized earth element (REE) patterns, which we interpret as evidence for their refertilization boninitic melts a wedge. Geochemical suggests that parental magmas high-Cr podiform chromitites (Cr#Sp = 71–83) were composition. host platinum-group mineral (PGM) assemblage laurite [Ru# = 64.0–90.7] Os-Ir alloys, indicating crystallization within range fS2 conditions (logfS2 ∼ −2 −1.3) Tmax ∼1200 °C. Mineral compositions geochemical data basalts show tholeiitic alkali compositions. tholeiites mildly light REE depleted patterns Th/Yb La/Nb ratios indicate presence sediment component, implying subduction-related origin. Petrogenetic modeling indicates resulted 20% melting spinel-bearing asthenospheric mantle. initial eNd values 7.2 4.9 two tholeiite samples asthenosphere more enriched sources probably due input older sediment. A comparison other complexes subduction-overprinted seen immature island arcs. trace similar OIB origin unrelated assemblage. composition can be modeled mixing low-degree (1–2%) garnet-bearing lherzolite (GLS) melt fractions (SLS) at variable proportions (GLS/SLS = 7/10–1/10). We propose following tectono-magmatic model petrogenetic evolution ophiolite: i) oceanic ridge spreading generated MORB type (not observed our sample collection), (ii) deep beneath crust OIB-like Neo-Tethyan basin, (iii) subduction initiation formation infant forearc basin formed arc boninites.