Türkiye Jeoloji Bülteni

Petrography, Metamorfhism and Genesis of Metamorphics in the Çökekyazı Gökay (Hizan, Bitlis) Area of the Bitlis Massif

Abstract: Çökekyazı-Gökay area comprises the "lower unit" and the "upper unit" metamorphics of teh Bitlismassif. The lower unit metamorphics include various schists, gneisses and amphibolites as well as metaquartizites andmarbles, whilst the upper unit consists of micaschists, chloriteschists, metaquartzites, calcschists and marbles. Theupper unit rocks of the Upper Paleozoic possibly Permian age rest upon the older lower unit with an angular unconformity. These metamorphics, mapped on a 1/25.000 scaled map via fieldwork in different times, have been studied microscopically and geochemically. Thus, facies conditions affecting teh metamorphics in the district end mineral assemblages developed under these conditions have been determined and parent rocks elaborated. Studies have shown that mineralassemblages of both the amphibolite and greenschist facies co-exist in tha lower unit rocks. This situation probablyoriginates from the partial superimposition of the Post-Permian greenschist facies metamorphism onto the Pre-Permianamphibolite facies metamorphic activity. In the upper unit metamorphics, minerals of the greenschist facies are onlyseen and it is obvious that this was the Post-Permian metamorphism also affecting the lower unit rocks.Both fieldworkand data obtained throngh geochemical analyses have indicated that some gneisses and amphibolites in the region werethe derivatives of sedimentary, whilst the others were derived from igneous rocks. The various schists, metaquartzite andmarbles come from sedimentary origins.