Petrology of the Kurancali Phlogopitic Metagabbro: An Island Arc-Type Ophiolitic Sliver in the Central Anatolian Crystalline Complex

The Kurancali metagabbro occurs as an isolated body in the central part of the Central Anatolian Crystalline Complex. It has been emplaced along a steep S-vergent thrust-plane onto the uppermost units of the Central Anatolian Metamorphics. The main body of the Kurancali metagabbro is characterized by distinct compositional layering. The layered gabbros comprise pyroxene and hornblende gabbros. Phlogopite-rich, plagioclase-hornblende gabbro occurs mainly as pegmatitic dikes intruding the layered gabbro sequence. The layered gabbros, in general, consist mainly of diopsidic augites, brown hornblendes, and plagioclase. Secondary phases are phlogopitic mica, brownish-green hornblende replacing clinopyroxenes, and fibrous, greenish actinolitic hornblende partially or completely replacing brown hornblende. The primary dark micas are phlogopitic in the range of phlogopite(57-70) and annite(30-43). The analyzed pyroxenes are diopsidic (En32Fs19Wo49-En35Fs18Wo48). The whole-rock geochemistry of the gabbros indicates the presence of two distinct groups of rocks; a less pronounced group of phlogopite gabbro with island-arc calc-alkaline affinities, and a dominating layered gabbro sequence with island-arc tholeiite characteristics. They are extremely enriched in LILE, indicative of alkaline metasomatism in the source region, and display geochemical features of transitional backarc-basin basalts (BABB)/island-arc basalts (IAB)—and IAB-type oceanic crust. Based on their geochemical similarities to modern island-arc basements, we suggest that the Kurancali metagabbro may represent the basement of an initial island arc, generated in a suprasubduction zone setting within the Izmir-Ankara branch of Neotethys.