PETRO-MECHANICAL STUDIES OF THE STRATIGRAPHIC UNITS OF THE TARKWAIAN SUPERGROUP IN TARKWA – IMPLICATIONS FOR THE STRUCTURAL AND MECHANICAL COMPETENCE OF ROCKS

Abstract

Main purpose of this paper is to determine the mineralogical composition and mechanical properties of the Tarkwaian Supergroup and compare them. This project will help determine whether the rock units of the Tarkwaian Supergroup are competent based on their mineral contents and strength of the rocks to be quarried and used as aggregates for construction and also determine the structural features that were formed in the various rock units due to the deformation that took place. Values obtained from the Unconfined Compressive Strength (UCS) test were (21.50-77.10) N/mm2 with the Kawere conglomerate having the lowest, and Tarkwa Phyllite having the highest strength. The Huni sandstone, Banket Quartzite and Kawere conglomerate were classified as weak rocks, but the Tarkwa Phyllite was classified as a medium rock, according to Attewell and Farmer’s (1976) classification. The Huni sandstone, Banket Quartzite and Kawere conglomerate are made up of grains of varying degrees of roundness and maturity. The Huni sandstone, Banket Quartzite, and Tarkwa Phyllite exhibit foliation. Micro-folding is also observed in the Kawere conglomerate. Petrographic studies of the rocks classify them as metasedimentary rocks weathering. Based on the weak strengths of the various rock units, they are not suitable to be used as aggregates for construction but can be used for other purposes such as construction sand and dimension stones.