The origin and evolution of the Menderes Massif, W-Turkey: A rubidium/strontium and oxygen isotope study

Abstract

Das Menderes Massiv ist ein alpinotypes Gebirge derWest-Tfirkei und besteht aus drei tektonisch-lithologischen Einheiten, die in den ,,Gneisskern, und in die ,,Schieferhfille,~ und ,,Marmorhfille,~ gegliedert werden. Diese Arbeit berichtet fiber Isotopenanalysen, die an einer metasediment/iren und migmatitischen Gesteinsserie yore Sfidrand (Typ A) und an einer metatonalitischen bis metagranitischen Gesteinsserie yore Nor&and des Menderes Massivs (Typ B) durchgefiihrt wurden.Die Rb-Sr-Gesamtgesteinsisochrone der Gesteine (Typ A) definiert ein Alter yon 502 + 10 Ma und ein initiales S7Sr/S6Sr-Isotopenverh~.lmis yon 0.71174 _+ 73. Dieser AIterswert wurde als Zeitraum der Migmatisierung interpretiert. Die Rb-Sr-Gesamtgesteinsisochrone der Gesteine (Typ B) ergibt ein Alter yon 471 __ 9 Mabei einem initialen 87Sr/86Sr-Isotopenverh~ilmis yon 0.70684 +_ 25, wobei dieser Alterswert als Intrusionsalter gedeutet wird.Der Zeitraum der Kristallisation alpiner Mineralparagenesen wird dutch einen mittleren Rb-Sr-Hellglimmeralterswert yon 56 _ 1 Ma erfa~t. Die Hellglimmer aus dem Gesteinstyp B ergeben Rb-Sr-Mischalter yon 120-230 Ma, die im Zeitraum zwischen der mittelalpinen und der kaledonischen Metamorphose liegen. Die Biotite aus den beiden Gesteinstypen (A und B) definieren einen mittleren Rb-Sr-Alterswert yon 37 4-1 Ma, der als das alpine Abkiihlalter interpretiert wird.Die AbstractThe Menderes Massif, located in the Alpine orogen of Western Turkey, has three litho-structural units, a basal ,,gneiss core% a ,,schist mantle,~ covering the gneiss core, and an overlying ,,marble mantle~,. This study reports isotopic data from samples of rnetasediments and migmatites from the southern (Type A) and of tonalitic to granitic metaigneous rocks from the northern Menderes Massif (Type B).Type A rocks define a Rb/Sr whole rock isochron age of 502 q-10 Ma and an initial STSr/S6Sr ratio of 0.71174 _+ 73. This is interpreted as the age of migmatization. Type B rocks give a Rb/Sr whole rock isochron age of 471 _+ 9 Ma with an initial SVSr/S6Sr ratio of 0.70684 + 25, which we interpret as the intrusion age.K-White micas from rock type A give an average Rb/Sr mineral age of 56 +_ 1 Ma, which can be interpreted as the formation age of the Alpine mineral paragenesis. K-white micas from rock type B give Rb/Sr mixed ages of 120-230 Ma between Alpine and Pan-African orogenies. Biotites from both rock types yield an average Rb/Sr age of 37 4-1 Ma, which is interpreted as an Alpine cooling age.The oxygen isotope ratios of type A rocks range from 10.4 to 14.6%o, and of type B from 8.9 to 11.8%o. The oxygen and strontium isotopic compositions together clearly distinguish rocks of types A and B. Compositions of type A rocks suggest a crustal origin: type B rocks have compositions transitional between those of crustal and mantle-derived materials.

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

“…The Menderes Massif is intensely sheared during hightemperature and medium-pressure (Barrovian) metamorphism (the so-called Main Menderes Metamorphism, or MMM [Akkök, 1983;Ashworth and Evirgen, 1984;Sengör et al, 1984;Satir and Friedrichsen, 1986;Bozkurt and Park, 1999;Whitney and Bozkurt, 2002;Sengün et al, 2006]. This MMM postdates a phase of HP metamorphism and eclogite formation in mafic pockets in the Pan-African orthogneisses Candan et al, 2001] and also postdates HP metamorphism [Régnier et al, 2007] under blueschist facies conditions Oberhänsli et al, 1998;Rimmelé et al, 2003b;Whitney et al, 2008] in the Paleozoic to Eocene sedimentary cover.…”

Occurrence of primary almandine-spessartine-rich garnet and zinnwaldite phenocrysts in a Neogene rhyolite on the island of Chios, Aegean Sea, Greece

“…This may have been responsible for the more alkaline (potassic) character of the volcanism in the eastern Aegean. It has been shown from isotopic studies (Stouraiti et al, 1998;Altherr et al, 1988;Satir et al, 1986) that the granitoids of the eastern Aegean have a higher proportion of enriched mantle component relative to the western arc magmatic rocks, as a result of this different tectonic regime. It is suggested that this is associated with a rather specific tectonic setting in the broad eastern Aegean area, including Kos-Samos-Patmos-Chios and Bodrum, in a zone extending broadly in a N S orientation, that is transverse to the modern volcanic arc.…”

40Ar/39Ar geochronology, geochemistry and petrology of volcanic rocks from the Simav Graben, western Turkey

“…Sr and Nd isotopic ratios obtained from the MCC vary from 0.71655 to 0.86800 and 0.51218 to 0.51283, respectively (Satır and Friedrichsen 1986;Ersoy et al 2012a;Çoban et al 2012), which are clearly distinct from the magmatic rocks in the region. Hence, even low-degree contamination of the parental magmas by rocks of the MCC would yield magmas with very high 87 Sr/ 86 Sr ratios.…”