Discussion on the evolution of the Southern Menderes Massif in SW Turkey as revealed by zircon dating

Abstract

Scientific editing by Randy Parrish. Erdin Bozkurt & Graham Park write: ⇓Loos & Reischmann (1999) employ geochronological evidence (single zircon ages) from the augen gneisses of the southern Menderes Massif (SW Turkey) to conclude that the granitic precursors were intruded between c.  521 and 572 Ma (averaging 550 Ma) during the Late Precambrian and Early Cambrian. They claim that this evidence contradicts the views of ⇓Bozkurt et al. (1993, ⇓1995) and ⇓Bozkurt & Park (1994) who provided the first field evidence for the intrusive nature and Tertiary age of the granitic protolith of the gneisses. In a complex polydeformed environment like the Menderes Massif, reliance on geochronological evidence alone can be seriously misleading, and any viable geological model must satisfy both geochronological and field constraints. We would point out that similar ‘old’ zircon ages are widely known from the literature (⇓Reischmann et al. 1991; ⇓Loos & Reischmann 1995; ⇓Hetzel & Reischmann 1996; ⇓Dannat & Reischmann 1998; ⇓Hetzel et al. 1998; ⇓Koralay et al. 1998) and that it was emphasized in our papers (⇓Bozkurt et al. 1993, ⇓1995; ⇓Bozkurt & Park 1994, ⇓1997 a , ⇓ b ) that these ages apparently contradict the intrusive contact relations between the metagranites and the structurally overlying metasedimentary envelope. Loos & Reischmann confirm the presence of an intrusive contact close to Lake Bafa but question the intrusive contact relations in the Selimiye (Milas) area described by us. They claim that the interference of various deformation phases led to the formation of tectonic lenses of the augen gneisses within the schists and vice versa, and suggest that it is these structures that we (⇓Bozkurt et al. 1993, ⇓1995) interpreted as intrusive contacts. However we would emphasise that the intrusive contacts described in …