Effect of Sericitization on the Engineering Properties of the Miango Granite Porphry, North Central Nigeria

Abstract

The effects of sericitizaition on the engineering properties of the Miango Granite porphyry located in Bassa Local Government Area (L.G.A), Plateau State, Nigeria was carried out. The tests carried out on the twenty rock samples include; aggregate crushing and impact tests, water absorption, durability tests, specific gravity and petrographic examination. An average aggregate crushing value of >20% for most of the rock samples show that the rocks are relatively weak while other tests such as aggregate impact values of 18%-23%, water absorption of <1%, durability test (soundness values) of <12% and specific gravity values are fairly good. However, thin section studies revealed three distinctive features which greatly influence the physicomechanical properties: (a) abundant fractures of varying sizes (b) sericitization of the orthoclase/plagioclase feldspars (c) intergrowth of quartz with plagioclase or orthoclase feldspars. The strength loss of the granite porphyry could be attributed to the presence of micro-fractures on the rock samples and the sericitization of the dominant plagioclase and orthoclase feldspars. Geotechnical characterization of the rocks shows that they can be utilized as roadstone or could be cut and polished and used as facing stones because of slow disintegration to sulphate attack and the large feldspar phenocrysts in the rock samples.