Tectonic significance of the geochemistry and petrology of the Tekirova (Antalya) ophiolite, Southern Turkey

10th International Multidisciplinary Scientific Geoconference and EXPO, SGEM 2010 --20 June 2010 through 26 June 2010 -- Varna --The Tekirova (Antalya) ophiolite is located at the southwestern part of the Antalya complex along the Tauride belt in southern Turkey. The Tekirova (Antalya) ophiolite pseudostratigraphy such as, in an ascending order: harzburgitic tectonites, ultramaficmafic cumulates, isotropic gabbros and sheeted dikes. Comagmatic volcanics rocks in the Tekirova ophiolite are not preserved and metamorphic sole rocks under the harzburgitic tectonites. Numerous isolated dikes, ranging in thickness from 5 cm to 10 m, intruded the crustal rocks at different structural levels. The ultramafic-mafic cumulate rocks are composed of wehrlite, lherzolite, olivine clinopyroxenite, olivine gabbronorite, olivine gabbro, gabbronorite and gabbro. These rocks are characterized by igneous layering-lamination, cross-bedding, graded bedding, isoclinal folding and slump structures. The crystallization order within the cumulates is olivine (Fo88-76)±chromian spinel, clinopyroxene (Mg#92-76), orthopyroxene (Mg#86-70), plagioclase (An97-84). The presence of high Ca-plagioclase, highly magnesian olivine, clinopyroxene, orthopyroxene and their coexistency in the cumulate gabbroic rocks are indicative of subduction-related tectonic environment and suggest that the cumulates of the Tekirova ophiolite were derived from an island arc tholeiitic (IAT) magma. The isotropic gabbros are represented by gabbro, diorite and quartz diorite rocks with granular to ophitic-subophitic textures. The isolated dikes are characterized by dolerite, diabase and microdiorite with ophitic, intersertal and microgranular textures. The major and trace element geochemistry of the isotropic gabbros and isolated dikes show three different magma types. These are (i) IAT series comprising the Group I isotropic gabbros and sheeted dikes; (ii) Low-Ti boninitic series characterized by the Group II isotropic gabbros and sheeted dikes; (iii) OIB-type including the Group III isotropic gabbros. All the geochemical evidence suggests that the oceanic crustal rocks of the Tekirova (Antalya) ophiolite were generated from progressive source depletion from island arc tholeiites (IAT) to boninites and formed in a fore-arc tectonic setting during the closure of the southern branch of the Neotethys in Late Cretaceous