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Turkish Journal of Earth Sciences

UTKU BAĞCI

DOI

10.3906/yer-1203-1

Abstract

The regionally important dismembered ophiolitic sequence from the southern Kahramanmaraş region, located along the Arabian-Eurasian collision zone in southeastern Turkey, contains harzburgitic tectonites, ultramafic to mafic cumulates, isotropic gabbros and ophiolite-related metamorphic rocks. The ultramafic-mafic cumulate rocks are composed of wehrlite, lherzolite, olivine websterite, olivine gabbronorite, olivine gabbro and gabbro. The crystallization order of the cumulus phases, the presence of high Ca-plagioclase (An_{83-94}), highly magnesian clinopyroxene (Mg#_{78-93}), olivine (Mg#_{71-91}) and their coexistence in the ultramafic-mafic cumulate rocks indicate a suprasubduction zone (SSZ) environment and suggest that the cumulates were derived from an island arc tholeiitic (IAT) magma. The isotropic gabbros are mainly represented by hornblende gabbro, gabbro and diorite rocks. The major and trace element geochemistry of the isotropic gabbros reveals two different magma types. The first group is characterized by low TiO_2 (0.91-1.52 wt.%) and Zr (35-79 ppm), and REEs exhibiting flat to slightly depleted LREE (La_N/Yb_N = 0.38 to 0.67) patterns, geochemically similar to island arc tholeiites. The second group is characterized by higher TiO_2 (2.67-3.87) and Zr (176-351 ppm) and displays significant LREE enrichment (La_N/Yb_N = 10.9 to 14.5) patterns, which are geochemically similar to oceanic island basalt (OIB). Metamorphic sole rocks are represented by alkali amphibolites and are similar to OIB. All the evidence suggests that the ophiolitic rocks of the southern Kahramanmaraş region are associated with different types of magma generation and were emplaced onto the Arabian passive margin along the southern branch of the Neotethys oceanic basin during the Late Cretaceous.

Keywords

Suprasubduction, island arc tholeiite, alkaline, cumulate, ophiolite, Turkey

First Page

536

Last Page

562

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