Mineral Chemistry of Chlorite and Illite/Mica in the Clastic Rocks of Karakaya Complex: Origin and Diagenesis/Metamorphism

Abstract

The Karakaya Complex units representing the relicts of environments related with the closure of PreJurassic Paleotethys Ocean outcrop within the Sakarya Composite Terrane. The compositions of illite/white micas change among muscovite-illite-phengite that illite/white micas with detrital and authigenic origins are close to muscovitic (Si-avg = 3.15, (Na+ K) avg = 0.81) and illitic compositions (Si-avg = 3.22, (Na+K)(avg) = 0.74), respectively. Paragonite (Si-avg = 2.96, Na= 0.78, K= 0.10) and NaK micas (Si-avg = 3.09, Na= 0.45, K= 0.34) are typical for extentional basins that are determined in the upper parts of the Turhal Metamorphites corresponding to the subgreenschist facies of the Karakaya Complex. The chlorites are of entirely trioctahedral and authigenic ones (Si-avg = 5.67, Fe avg = 5.05) have higher SiIVand lower FeVI contents in comparison with detrital ones. Chlorites have chamositic in the Hodul Unit, whereas clinochlore composition in the Orhanlar Unit. Detrital micas with high Mg (5.70-7.59) and Cr (0.09-0.16) contents are also identified in the Orhanlar Unit more common and in the Turhal Metamorphites as a few grains that are evaluated as evidences the presence Pre-Triassique ophiolitic rocks. The data of chlorite chemistry indicate the origins of felsic for Turhal Metamorphites, metabasic (probably remains of Paleotethys) for Orhanlar Unit and felsic and metapelitic with rich in Al and extreme rich in Fe. The data of chlorite geothermometry and phengite geobarometer indicate a temperature ranging from 150 to 300 degrees C and a pressure between 0.5-1.2 kbar, respectively. These values reflect the the high temperature-low pressure metamorphism for the upper part of the Karakaya Complex representing sub-greenschist facies and low-middle temperature-low pressure diagenesis conditions for sub-greenschist facies units of the Karakaya rift.