Writers : M. Rahgoshay, I. Monsef, H. Shafaii Moghadam& M. Mohajjel
Refference : Geosciences Scientific Quarterly Journal,No.:63,P.:2
Publishing Year : 1385

Abstract :
Petrofabric, structural and geochemical study of the ultramafic tectonites in the Khoy ophiolitic complex suggest that these tectonites including low-temperature NW-SE shear zones cut the high-temperature to medium-temperature NE-SW mantle flow direction. Microstructures in these tectonites, record a fabric transition from oblate porphyroclastic and oblong porphyroclastic textures (related to the high- and medium-T deformations in mantle sections) to mylonitic textures (with low-T deformation in the shear zones). The study of olivine LPO patterns in high- and medium-T deformation samples of mantle shows slip on the (010) [100] high-temperature-low stress and (0kI) [100] moderate-temperature systems (up to 10000) while olivine LPO patterns in the low-I deformation samples within the shear zones indicate gliding along (001) [1001 low-temperature slip system (800-900°). Spinels in these peridotites show high variations in Cr number (10 to 90) and Mg number (50 to 90). Cpxs rich in Cr suggest a low degree of partial melting in these peridotites. The very variable composition of the spinels may be the result of partial melting process and recrystallization of these minerals in the mantle lithosphere during the detachment phase and the development of the shear zones.
Subject List : Structural evolution