Granitoid rocks of the southern Menderes Massif (southwestern Turkey): field evidence for Tertiary magmatism in an extensional shear zone

Abstract

Recent field campaign in the southern Menderes Massif in southwestern Turkey revealed that the socalled 'core of the massif' comprises two distinct types of granitoid rocks: an orthogneiss (traditionally known as augen gneisses) and leucocratic metagranite, where the latter is intrusive into the former and the structurally overlying 'cover' schists. These differ from one another in intensity of deformation, degree of metamorphism and kinematics. The orthogneiss display penetrative top-tothe-N-NNE fabrics formed under upper-amphibolite facies conditions during the Eocene main Menderes metamorphism (MMM), whereas foliation and stretching lineation exists in the leucocratic metagranites but are not strongly developed. The leucocratic metagranites show evidence of syn-to post-emplacement deformation in a series of weakly developed top-to-the-S-SSW fabrics formed under lower greenschist-facies (?) conditions. Leucocratic metagranite bodies occur all along the augen gneiss-schist contact in the southern Menderes Massif; they are emplaced as sheet-like bodies into country rocks (previously deformed and metamorphosed during a topto-the-N-NNE Alpine orogeny) along a ductile extensional shear zone, located between orthogneisses and metasediments, which was possibly active during emplacement. The data presently available indicate that emplacement and associated ductile extensional deformation occurred during Late Oligocene-Early Miocene time. These results confirm previous contentions that there are Tertiary granites in this part of the Menderes Massif.

Late Neoproterozoic granulite facies metamorphism in the Menderes Massif, Western Anatolia/Turkey: implication for the assembly of Gondwana

“…550 Ma, a pre-550 Ma age is postulated for the partial melting of basement . Additionally, the basement series of the Menderes Massif is characterised by the existence of widespread post-granulitic orthogneisses, which were derived from voluminous granitoid intrusions (Bozkurt, 2004;Bozkurt, Winchester, & Park, 1995, Bozkurt et al, 2006Gessner et al, 2004;Hetzel & Reishmann, 1996;Loos & Reıschmann, 1999;Koralay, 2004Koralay, , 2012. Recent studies have revealed that the main peak of this acidic magmatic activity can be constrained between 550 and 540 Ma Koralay 2012).…”

Exhumation with a twist: Paleomagnetic constraints on the evolution of the Menderes metamorphic core complex, western Turkey

“…[25] In the southern Menderes Massif, we collected seven sites from one leucogranite intrusion near Kafaca, described by Bozkurt [2004], who concluded that the age of this granite should at least be younger than a 36 ± 2 Ma cooling age reported by Lips et al [2001]. Additionally, we collected four sites from undated leucogranitic dikes near Sakarkaya and Kayabükü.…”

An overview on the main stratigraphic and structural features of a geothermal area: the case of Nazilli-Buharkent section of the Büyük Menderes Graben, SW Turkey

“…Beyşehir-Hoyran and Lycian Nappes) towards further south and their first emplacement onto the marine Eocene sequence and lastly onto the Lower-Middle Miocene marine clastics, (c) the overthickening of the lithosphere (up to 50-55 km) (Şengör, Satır, & Akkök, 1984), d) the Barrovian type of regional metamorphism (MMM: the main Menderes Massif metamorphism) (Bozkurt, 1996;Bozkurt, 2004;Bozkurt & Park, 1999;Brunn et al, 1971;Koçyiğit, 1983;Okay, 1986;Özgül, 1984;Şengör & Yılmaz, 1981;Sözbilir, 2005), (e) a very rapid regional uplift and deposition of 2-km-thick boulder-block conglomerate in the nature of molasse (Koçyiğit, 1984) and (f) exhumation of the Menderes Massif. This long-lived contractional deformation period was also accompanied by a widespread collisional to post-collisional magmatic activity and related felsic intrusions such as batholith, stock and dome (Bozkurt, 2004;Bozkurt & Park, 1997a;Bozkurt, Park, & Winchester, 1993;Emre & Sözbilir, 2005;Erkül, Helvacı, & Sözbilir, 2005;Ercan et al, 1985;Genç, 1998;Glodny & Hetzel, 2007;Harris, Pearce, & Tindle, 1986;Jolivet & Brun, 2010;Karacık & Yılmaz, 1998;Seyitoğlu & Scott, 1991;Wilson & Bianchini, 1999) which added a considerable amount of thermal anomaly to the over-thickened lithosphere, and so, triggered the orogenic collapse (Dewey, 1988) and the emergence of tensional forces (Dewey, 1988;Pinet & Colletta, 1990). Consequently, the contractional period was replaced by the tensional tectonic period during Late OligoceneEarly Miocene (Koçyiğit, 2005;Koçyiğit, Yusufoğlu, & Bozkurt, 1999;Seyitoğlu & Scott, 1991).…”

“…The nature of the discontinuity or contact between the so-called "Core" and "Cover" rocks is still under debate. There are three ideas about it: (1) it is a regional unconformity (the supra Pan-African unconformity) (Şengör, Satır, & Akkök, 1984), (2) it is a south-facing extensional shear zone including preserved igneous contact along which Oligo-Miocene granites were intruded into the cover rocks (Bozkurt, 2004;Bozkurt, Park, & Winchester, 1993;Bozkurt & Satır, 2000;Hetzel & Reischmann, 1996); these authors have also reported that the core rocks had been exhumed into their present-day positions in the footwall of this shear zone during a top-to-the SSW operating deformational event of Oligo-Miocene age, and (3) it is a south-facing thrust fault contact (Gessner et al, 2001;Ring, Gessner, Güngör, & Passchier, 1999). The Menderes Massif has attained its massif character under the high-T (500°)/ moderate-P (≤5 kbar) conditions or Barrovian-type of tectono-metamorphic event termed "main Menderes metamorphism (MMM)" (Whitney & Bozkurt, 2002).…”

“…it occurred during Eocene. It has been reported that the MMM was a result of deep burial of the massif beneath the tectonically southward moving Lycian Nappes rooted from the northerly located İzmir-Ankara-Erzincan Neo-tethyan suture zone (Bozkurt, 1996(Bozkurt, , 2004. The tectonic load of the nappe caused a regional metamorphism (MMM) and deformation of the massif area during Eocene (Şengör, Satır, & Akkök, 1984;Şengör & Yılmaz, 1981).…”