Mineralogical-geochemical investigation of the chromite deposits and the relationship between chromite occurrences and country rocks on the Kop mountain (NE Turkey)

In this study, the occurrence of chromite deposits and their mineralogical-petrographical and geochemical relationship with their surrounding rocks were investigated in Late Cretaceous aged Kop ultramafics (NE Turkey). The study was performed at two selected areas covering dunitic and harzburgitic outcrops.The Çamlıtepe and vicinity as one of the studied area consists of mainly dunite and pyroxenites, and has large chromite deposits in dunitic area. The Delavlar Mountain and vicinity as second studied area consists of mainly harzburgite and pyroxenites, and has small chromite deposits surrounded by dunitic envelops within harzburjite.Dunites are heavily serpantinized, harzburgites are moderately serpentinized and pyroxenites are rarely serpentinized. Olivines in dunites are serpentinized almost completely with relict primary textures. However, primary textures are observed commonly in harzburgite and pyroxenite. Orthopyroxenes in harzburgites are enstatitic whereas clinopyroxenes in clinoproxenite and websterite are diopsitic in composition. Olivines in dunites and harzburjites are generally forsteritic in composition.Chromite in the chromitites and accessory chromites in the peridotites show alpine type characteristics. Based olivine and chromite mineral chemistry in the peridotites; harzburgite plots in the olivine-spinel mantle array whereas dunite is inconsistent with this array. Similarly, chromite mineral chemistry in both peridotites suggests that the harzburgite is depleted peridotite in origin but the dunite is related to boninitic magmas. While whole-rock trace and rare earth element pattens of harzburgite and pyroxenite, compared to boninitic rocks, pyroxenites can be related to boninitic magmas and have derived from harzburgitic rocks. It may be suggested that a paleo-subduction was important in the formation of chromite occurrences although there is no data about its dipping direction.