Petrographic and physico-mechanical characteristics of granitoids at Northwestern Margin of the Kohistan Island Arc

The porphyritic granite, coarse-grained foliated granite, and fine-grained granite around the Bibior area were studied to establish the relationship between their petrographic features and physico-mechanical properties. Field observations revealed that the granitoid rocks were generally coarse-grained and porphyritic in texture, with fine-grained equigranular and coarse-grained foliated varieties. Petrographic examination indicates that these granitoids are essentially composed of quartz, plagioclase, and alkali feldspar, which also occurred as groundmass in some of the analyzed samples. The accessory mineral assemblage consists of biotite, muscovite, and hornblende with a trace amount of sericite, chlorite, opaque-ore minerals, zircon, titanite, epidote, apatite, garnet, and hematite. Quartz grains predominantly exhibit undulose extinction, indicating deformation and strained conditions. The behavior and durability of the granitoids as construction materials using physical and mechanical properties were studied, including water absorption, specific gravity, porosity, unconfined compressive strength (UCS), and unconfined tensile strength (UTS). Three different texture varieties were studied, which revealed that these rocks had average values of water absorption 0.25-0.32 %, bulk specific gravity 2.68-2.71 Kg/cm3, porosity 0.67-0.87 %, UCS 72.3-129 MPa, and UTS 5.74-13.45 MPa. The statistical analysis of petrographic and physio-mechanical properties shows that the mineral composition, texture, and lower amount of flaky minerals made these rocks stronger, followed by fine-grained granitoid rocks having higher strength values compared to the porphyritic rocks. The overall physio-mechanical assessment suggests that the Bibior Granitoids can be used in construction applications, particularly as dimension stone and embankment fill material.