Multi-Stage Evolution of Forearc Mantle Peridotites of Kagizman Ophiolite (agri-Eastern Anatolia)

Abstract

The Kagizman Ophiolite, constituting the easternmost part of Tethys ophiolites in Anatolia, is located on the Izmir-Ankara-Erzincan ophiolitic belt. Ophiolitic rocks include a range of mantle peridotites, gabbros, pillow basalts and isolated sheeted dykes. The studied mantle peridotites are investigated with regard to geochemical and petrographical characteristics. MgO content of peridotites varies from 41.24 to 45.63 wt % while that of Al2O3 is in the range of 0.20-0.32 wt % indicating a high partial melting degree. Highly depleted mantle peridotites represent residues of primitive mantle formed by 17-23% melting. Whole rock trace element patterns point to variable partial melting conditions. Petrographical and geochemical results reveal that mantle peridotites of Kagaman Ophiolite are the residues of two-stage partial melting process. The first melting (consuming) stage occurred in a mid-ocean ridge setting which was later metasomatized in a subduction zone by interaction between peridotites and fluids derived from the subducted crust. According to all data, these rocks are hypothesized as forearc peridotites affected by high degree partial melting.