Abstract:
The Bibior area belongs to the western part of Kohistan Batholith in Kohistan
Island Arc. Geographically the area is located at the south of the Dir Town, Upper Dir
District, NW Pakistan. The rocks exposed in the study area are mainly granites, and
amphibolites. The granitic rocks i.e., porphyritic granite, coarse-grained foliated granite,
and fine-grained granitearound the Bibior area were study to determine their
petrographic characteristics and mechanical properties. Field observations and
petrographic examination revealed that the granitic rocks were broadly porphyritic in
texture. However, fine-grained equigranular and coarse-grained foliated varieties were
also found at places.
The petrographic examination showed that the porphyritic granite, foliated
granite and fine-grained granite are essentially composed of quartz, plagioclase, and
alkali feldspar which also contributed as ground-mass in some of the representative
samples. The minor mineral assemblage is biotite, muscovite and hornblende with
accessory amount of sericite, chlorite, opaque-ore minerals, zircon, titanite, epidote,
apatite, garnet, and hematite. The quartz grains mostly display undulose extinction and
are strained. To determine the behavior and durability of the granitic rocks as
construction materials, 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 (fine-grained
granite, coarse grained foliated and porphyritic granite) were study according to ASTM
practices, and the tests revealed that these rocks had average values of water absorption
0.255-0.326%, specific gravity 2.680-2.710 kg/cm3, porosity 0.675-0.87%, UCS 72.3-
129MPa, andUTS 5.74-12.23MPa.The petrographic and physico-mechanical properties
relationship through statistical analysis shows that the mineral composition, texture, and
lower amount of flaky minerals make rocks stronger. The fine-grained granitic rocks
from Bibior area having higher strength values due to their finer grain size compare to
coarse-grained foliated and porphyritic varieties.The strength tests show that allvii
varieties from the area can be used in construction projectssuch as dimension stone and
embankment fill.