THE INDEX MINERALS AND MINERAL ASSEMBLAGES DETERMINED IN METAMORPHITES OF EVCİLER-ÇATKÖY (ÇAYIRALAN-YOZGAT) SEGMENT OF AKDAĞMADENİ MASSIF

Abstract

In the studied area, which is representing some part of metamorphic rocks of Akdağmadeni massif, some index minerals and mineral assemblages reflecting progressive regional dynamo-thermal metamorphism have been determined. In the metapelites belonging to the bottom levels of metamorphic rocks, the index minerals such as biotite, garnet, staurolite. kyanite. orthoclase and sillimanite and their assemblages have been determined; in the semi-pelitic rocks which take place above the metapelitic series we see index minerals such as plagioclase, calcite, diopsite, hornblende, tremolite and their assemblages with the increasing carbonate in environment. In the metacarbonates that we see widely at the top most of metamorphic series, the mineral groups such as calcite, epidote, plagioclase, diopsite and tremolite were found and they reflect metamorphism conditions. In the mineral assemblages originated from various amphibolites found almost in every lithology of metasedimentary sequence as intercalations and lenses, we see hornblende, plagioclase and garnet as index minerals. Looking at the experimental formation conditions of the mineral assemblages mentioned above, we could say that the metamorphic rocks of the studied area were formed under the progressive regional dynamo-thermal metamorphism conditions. It is pointed out by looking at the index minerals and mineral assemblages in metapelitic derivatives, metamorphism has occurred at 400-700 °C temperature and 3.5-6.5 kb pressure conditions progressively. The mineral assemblages found in semi-pelitic derivatives and metacarbonates also show a progressive metamorphism of 350-600 °C and medium-high grade. The mineral assemblage we see in the lithologies such as amphibolites reflects about 600 °C temperature and 6 kb pressure conditions.