Abstract
The study area comprised the rocks of the Kamila amphibolite belt, which constitutes the southern portion of the Kohistan Island Arc. Field examinations and microscopic analysis of the representative samples divulge that the area comprises the two major lithologies, i.e. hornblende gabbro-norite and altered gabbro-norite. Altered gabbro-norite exhibit porphyritic texture and the grains are subhedral. Plagioclase (66-75%) is the common essential mineral of altered gabbro-norite while muscovite (3-4%), quartz (7-12%), epidote (10%), clino-zoisite (1%) and garnet (3-5%) are accessory phases. Hornblende gabbro-norite is medium to coarse-grained, containing plagioclase (22-47%), ortho-pyroxene (12-16%) and clino-pyroxene (13-20%) as essential minerals whereas amphibole (9-20%), muscovite (1-15%), quartz (7-11%) and a few opaque minerals are found as accessory phases. The mechanical properties of the investigated samples are also part of this study. These properties include unconfined compressive strength, unconfined tensile strength, water absorption, specific gravity and shear strength. The unconfined compressive strength of altered gabbro-norite is 133.76 MPa and unconfined tensile strength is 15.2 MPa whereas unconfined compressive strength of gabbro-norites is 79.92-106.4 MPa and unconfined tensile strength ranges from 15.2 to 31.92MPa. Both rock types can be used as dimension stone and construction materials because both have high strength values. Comparison of the rock strength with their petrographic features reveals that grain shape and size, mineralogical composition, alteration products and micro-fractures have remarkable impacts on the engineering behavior of the studied rocks.
Keywords: Gabbro-norite; Kamila amphibolite belt; Kohistan island arc; mechanical properties; petrography.
