Tectonic Implications of Some Cretaceous Pillow Basalts from the North Anatolian Ophiolitic Mélange(Central Anatolia-Turkey) to the Evolution of Neotethys

Authors: BORA ROJAY, KENAN M. YALINIZ, DEMİR ALTINER

Abstract: The most widespread blocks within the North Anatolian ophiolitic mélange of central Anatolia (Turkey) are ophiolitic fragments, Jurassic-Cretaceous carbonate blocks and pillow basalts. The blocks of pillow basalts have an immobile trace-element geochemistry that is characteristic of ocean-island alkali basalts. An N-MORB-normalized spider diagram shows a distinctive enrichment of most incompatible trace elements and exhibits a far greater range of absolute abundances than N-MORB. Selected incompatible-element contents and ratios of basalts show high Ba/Nb (~8),low Zr/Nb(~5)and low La/Nb(~0.5)relative to N-MORB. The presence of thin-shelled \"Protoglobigerina\" and Cadosina associated with miliolids and epistominid foraminifers indicates that the age of the pink biomicritic carbonates deposited between the pillow basalt lobes is within the Callovian-Hauterivian interval. Collectively, these results support the presence of a seamount on the Neotethyan oceanic crust and prove the presence of an older oceanic crust along the northern branch of Neotethys.

Keywords: Seamount, Geochemistry, Callovian-Hauterivian Interval, Tethys, Ankara Mélange

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