Micro-tectonic Features of Simav Shear Zone, Northern Menderes Massif, Western Turkey

Abstract

Menderes massif is commonly affected by extensional regime and a good example of forming a metamorphic core complex. Simav detachment fault in the northern part of Menderes massif separated footwall and hanging wall rocks, which is thefeature of lithologic, metamorphism and deformation mismatch between them. The footwall consists of medium-high grade metamorphites, pegmatoids andgranitoids. Schist-marble unit and ophiolitic melange comprise the hanging wall. Neogene and Quaternary sedimentary and volcanic rocks lie both ımconformably and İn fault contact above the footwall and hanging wall rocks. Simav shear zone, characterized by deformed rocks below the Simav detachment fault, has two deformational
events; these are ductile (mylonitic) and brütle (cataclastic) deformations. Ductile deformation event is the formation ofvariably developed mylonites in the footwall The degrees of mylonite development vary from protomylonite to
blastomylonite. The majority of deformed rocks in the shear zone have mylonitic foliations and lineations. Mylonitic foliation is parallel and/or sub-parallel to the earlier foliation of metamorphic rocks. Mylonitic foliation is defined by preferred grain-shape orientation of biotite, muscovite and auartz ribbons. Lineation, other important element, is defined by stretched auartz, and preferred orientations of feldspars, kyanite, hornblende and mica grains. The common kinematic indicators found in the zone is asymmetric porphyroclasts, mica fish, S-C and S-C fabric, recrystallized oblique foliation, displacement grains and 'V'-pull-apart fabrics. These asymmetric structures indicate a top-to-theN-NE shear sense. Recrystallization, neo-mineralization and other deformational features of grains in the shear zone suggest medium-high-grade greenschist - amphibolite facies metamorphism conditions. Resent 40Ar39Ar isotopic dating implies that minimum age of shear zone is Oligocene - Early Miocene.
Progressive stage of extension regime in the region constitutes brittle deformation that involves the development of the cataclastic zone below the Simav detachment fault and high-angle normal faults in later stage. Cataclastic zone, describing an area here affected by brütle deformation in the detachment fault of footwall, include breccia/cataclasite that is product of mylonitic rocks of a variably fracturing, fragmentation, crushing, and alteration product. Exhumation of the northern part of Menderes massif was controlled by Simav shear zone. Structural, micro-tectonic features and izotopic data indicate that Simav shear zone is resultedfrom asymmetric exhumation of Menderes massif

Keywords

• Extension tectonic
• Menderes massif
• Simav detachment fault
• Mylonite Cataclasite
• Kinematic indicators

Kuzey Menderes Masifinde Simav Makaslama Zonunun Mikro-tektonik Özellikleri, Batı Anadolu, Türkiye

Abstract

Menderes masifi, genişleme tektoniği rejimi etkilerini yaygınca taşır. Bu bakımdan masif, metamorfık çe­kirdek kompleks oluşumuna iyi bir örnektir. Masifin kuzey kesiminde Simav sıyrılma fayı litoloji, metamorfızma ve deformasyon özellikleri birbirinden farklı tavan ve taban blok birimlerini ayırır. Sıyrılma fayının taban blok kayalarını orta-yüksek dereceli metamorfitler, pegmatoyidler ve granitoyid intrüzyonları oluşturur. Tavan blokta ise şist-mermer topluluğu ve ofiyolitli melanj kaya türleri bulunur. Tüm bu birimler havza kenarları faylanmalar ile sınırlı, Neojen Kuvaterner yaşlı volkano-sedimenter kayalar tarafından örtülür. Simav makaslama zonu sıyrılma fayının taban bloğundaki deforme alanları temsil etmekte olup, iki farklı defor­masyon evresi sunar. Bunlar sünümlü (milonitik) ve gevrek (kataklastik) deformasyonlardır. Deformasyonun sünümlü evresinde taban blok kayaları, değişen ölçülerde milonitleşme gösterir; Milonitleşme, protomilonit-milonit ultramilonit ve blastomilonit aralığında gelişmiştir. Burada sünümlü deforme olmuş kayaların en belirgin özelliği milonitik foliyasyon ve lineasyon göstermeleridir. Milonitik foliyasyon metamorfık kayalarda ilksel foliyasyona düşük açılarda oblik yada paralel gelişmiştir. Foliyasyon düzlemlerini biyotit, muskovit ile yassılaşmış kuvars mineralleri oluşturur.

Keywords

• Genişlemeli tektonik
• Menderes masifi
• Simav sıyrılma fayı
• Milonit

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