Tectonic significance of mafic volcanic rocks in a Mesozoic sequence of the Menderes Massif, West Turkey

Abstract

The Mesozoic platform sequence of the Menderes Massif consists of thick succession of detrital and carbonate rocks. In this sequence there are mafic metavolcanic rocks at two different levels. The first level of mafic metavolcanic intercalations is in the Late Triassic detrital-rich series located in the Çaltaşı Formation, which is the lowermost unit of the Mesozoic platform. The second level of the mafic metavolcanic rocks is located in the Late Cretaceous–(?)Paleocene Selçuk Formation laying on top of the platform sequence. The Çaltaşı Formation, which is composed of mica-schists, thinly-bedded cherts, calc-schist and mafic volcanic intercalations unconformably overlie the Bayındır Formation, which consists of mica-schists, phyllites, and white quartzites of Palaeozoic or probably older age. The mafic volcanic rocks in the Çaltaşı Formation are alkaline basalts with within plate characteristics and are formed during an intraplate extension. The Çaltaşı Formation is conformably overlain by the Kayaaltı Formation represented by calc-schists, dolomitic marbles, and rudist- and emery-bearing massive marbles in ascending order. The Selçuk Formation overlies the Kayaaltı Formation and consists of a mica-schist matrix with allochthonous blocks of mafic volcanic rocks, metaperidotites, metagabbros and massive marbles. The mafic volcanic rocks in the Selçuk Formation are tholeiitic basalts and are petrologically similar to mid-oceanic basalts. The geological and geochemical characteristics of the mafic metavolcanic rocks in the Çaltaşı Formation indicate that during the Late Triassic, the Menderes platform was segmented, probably by the opening of a branch of the Neotethyan Ocean. Between the Late Triassic and the Late Cretaceous, the Menderes carbonate platform was built up. During the Latest Cretaceous–Early Paleocene, a slab of oceanic crust obducted on this platform and provided slices of mafic metavolcanic rocks into the Selçuk Formation.