Geodynamic evolution of the Karakaya Mélange Complex, Turkey: A review of geological and petrological constraints

The Karakaya Complex in the pre-Liassic basement of the Sakarya Composite Terrane includes relicts inherited from the closure of the Palaeotethys. The interpretations regarding its origin are still controversial. The main reason for these controversies is largely due to the mélange character of the complex and the misidentification and misinterpretation of the tectonostratigraphic units that make up the complex. Kocyigit (1987) subdivided the complex into the Upper and Lower Karakaya Nappes. This tentative division assumes that the Upper Karakaya Nappe (Lower Karakaya Complex) is composed of rock assemblages metamorphosed under greenschist/blueschist facies. In contrast, the Lower Karakaya Nappe (Upper Karakaya Complex) is thought to be composed of relatively unmetamorphosed, yet deformed rock lithologies. In this study, our detailed geological and petrological observations show that subdivision of the Karakaya Complex based on differences in metamorphism does little to decipher the geological evolution of the complex. Supported by our recent findings (Sayit et al., 2010), however, we suggest that the mafic rocks in both Karakaya Nappes are actually similar to each other in terms of metamorphism and tectonic setting. We also propose that in classifying such chaotically mixed units, tectonomagmatic origin (together with age data) should be taken as the primary criterion, rather than metamorphism and deformation.

► The Karakaya Complex includes a number of mélange and/or tectonostratigraphic units.
► The Nilüfer Unit is characterized by OIB- and E-MORB-type metabasic rocks.
► The Eymir Unit forms the matrix in which the Nilüfer Unit is embedded.
► The Lower and Upper Karakaya Complexes are of similar origins.