Petrography and investigations on relation between deformation and metamorphism in metapelites of the Kuhe Arqoon, west of the Anguran lead-zinc mine, Zanjan Province
Subject Areas :Keywords: Deformation and metamorphism Metapelites Petrographic Kuhe Anguran. ,
Abstract :
The study area is located in the West of Anguran lead-zinc mine in Zanjan province, in the central Iran zone. The metamorphic rocks of the area include chlorite schist, epidote-amphibole schist, mica schist, marble, quartzite and metamorphosed gabbrodiorite. Metapelites are the focus of the present study, since they have recorded mineral appearances and deformational phases due to suitable composition. Petrographic studies show that three types of metapelites, including biotite schist, garnet schist and muscovite schist are present. Retrograde metamorphisms, owing to pressure and temperature decrease during exhumation are recorded in the Kuhe Arqoon rocks. The main deformational features include andaluse extinction, mineral stretching, pressure shadow and preferred orientation of minerals. Using petrographical studies and considering relation between structures and porphyroblasts and matrix (microstructures), three main deformational phases were determined for the area, among them the second deformational phase was the strongest. This deformation has produced the main foliation in the rocks. The weakest phase was the third deformational phase, which was not accompanied by metamorphism. Contemporarily with D1 deformational phase, M1 metamorphic phase occurred, crystallizing chlorite, muscovite, quartz, biotite and garnet. M2 metamorphic phase was coeval with D2 deformational phase. Mineral assemblage of M2 is biotite, muscovite, quartz and garnet. During the weak D3 deformational phase, chlorite is formed with weak orientation in the rocks.