ABSTRACT
The study area near Keban consists of the allochthonous Keban division of the Keban-Malatya crystalline complex and the Yuksekova island-arc rocks of the Bitlis-Puturge Complex in the northern margin of the Bitlis Suture Zone. Detailed mapping shows that the Palaeozoic-Triassic Keban Metamorphics are composed of the following formations: (1) white, massive, karstic Kirklar Marble; (2) phyllitic psammite with calcschist interlayers Calik Formation; and (3) semi-crystallized gray Koyunatlayan Limestone. These formations define a tectonostratigraphy with the Kirklar Marble at the base and the Koyunatlayan Limestone at the top. The detailed lithological description of the Keban Metamorphic rock assemblages suggest that they represent a deformed continental margin sedimentary sequence that has been metamorphosed to lower greenschist facies sometime in Jurassic to early Cretaceous times.
The Keban crystalline rock units were cut by a group of hypabyssal igneous rocks (syenite porphyry) which were produced during an extensional regime (rifting) in late Cretaceous. In the map area, the Campanian-lower Maastrichtian Yuksekova Volcanic rocks are represented by mafic extrusives and mafic volcaniclastics. They have experienced a low grade greenschist metamorphism.
In the Keban Metamorphics, structural data indicate at least two phases of penetrative deformational events (D1 and D2). There is also evidence for two non-penetrative tectonic deformations (Too and T3). The contacts between the metamorphic rock units are folded thrust faults (post-early Paleooene Pertek thrusting: Too) marked by fault rocks; no associated folding has been seen. Along the fault zones, a number of major mylonite and/or high-strain zones occur in the form of ductile shear zone, each up to few thousands of meters long and several meters wide. Besides the foliated mylonites, the fault rocks of the Keban Metamorphics are represented by fault breccias and gouge zones which display an incohesive random-fabric. Detailed structural analysis shows that the deformation mechanisms in each fault rock depends largely on its main mineral constituent. In the map area, from east to west, the N-S striking fault zones change from brittle-ductile shear zones into brittle zones with the western side of the zone showing less ductile features (eg. the Corik and Bezirgandere Faults) than the eastern side (eg. the Hirsiz and Gelintas Faults). D1 deformation phase is marked by tight to isoclinal folds (F1); associated foliation (S1: slaty cleavage and/or schistosity) and mineral elongation lineation (L1). D1 does not overprint any earlier deformation phase, but it does overprint the earlier tectonic structure (Too). It is overprinted by later D2 deformation phase. D2 is marked by open folds (F2 ); a crenulation cleavage (S2) and an intersection lineation (L2). They overprint both the earlier tectonic structure (Too) and the earlier deformation phase (D1).
In the study area, the contact between the Keban Metamorphics and the Yuksekova Volcanic Complex is a fault contact which strikes in N-S direction (the Keban Fault: T3). The structural analysis conducted along the Keban Fault shows that this is a sinistral strike-slip fault with a large thrust component. The age of the fault is determined as post-early Paleocene to medial Eocene. The Keban Fault is marked by brittle fault rocks, slickensides, mylonite and other foliated highly-strained ductile fault rocks. No folds associated with this tectonic structure have been seen.

Savci, G., 1983. Structure and Tectonics of the Keban Metamorphics in the northern margin of the Bitlis Suture Zone, Southeastern Turkey. Unpublished MSc. thesis, State University of New York at Albany. 201 pp., +viii; 5 folded plates (maps).
University at Albany Science Library call number:  SCIENCE Oversize (*) QE 40 Z899 1983 S29

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