Pakistan Journal of Geology (PJG)

Journal: Pakistan Journal of Geology (PJG)
Author: Hasnain Haider, Shamim Akhtar, Enayatollah Emami Meybodi

This is an open access journal distributed under the Creative Commons Attribution License CC BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

DOI: 10.26480/pjg.02.2025.117.120

Granite gneiss is the highest grade of metamorphic rock that exhibits prominent metamorphic structures. Susalgali granite gneiss has a foliated texture and contains small crystals of alkali feldspar (orthoclase or microcline). During field studies in this area few kinds of variations were also observed in granite gneiss i.e. highly porphyritic coarse-grained mica granite gneiss, medium grained micas granite gneiss, and leucocratic tourmaline-bearing granite gneiss. The petrographic studies of the granite gneiss indicate the presence of quartz, feldspar, biotite, hornblende, plagioclase and muscovite. Thin section studies also show fractional crystallization and zoning in plagioclase. In Pakistan, granite gneiss rocks are of diverse colors, mineralogy, textural characteristics, and mechanical properties could be found but limited literature available on the micro structures identification to explain the pressure-temperature conditions of granite gneiss. Microscopic techniques such as polarizing microscope and Scanning Electron Microscope (SEM) are combined to analyzed mineral composition, rock microstructure, and degree of metamorphism of selected quartz-rich samples. High-temperature recrystallization is indicated by the deformation and recrystallization of quartz. Microstructure identification indicates that feldspar boudins and quartz recrystallization occur at highest temperature and pressure.