The purpose of this study is to investigate dacites of different weathering grades from the Cakmakkaya and Damar open-pit\r\ncopper mines in northeastern Turkey based on their mineralogical, petrographical, and geomechanical characteristics. The dacites\r\nfor which surveys are carried out are mainly subjected to chemical weathering as well as physical disintegration and hydrothermal\r\nalteration. Discontinuities in this rock appear to be a major influence on the spatial distribution of weathering profiles, with the\r\nintensity of weathering increasing in the plagioclase phenocrystals and microlites as the weathering grade increases. The present\r\nresults show that the type and amount of clay minerals increase as the weathering grade increases. As the weathering increases, the\r\namount of mobile oxides, such as Na2O, MgO, and CaO, decreases while Fe2O3 and the loss on ignition (LOI) content increase\r\nfor most of the dacite samples. The microfracture frequency (qmf) may be a good indicator of fabric changes, and methylene blue\r\nadsorption (MBA) test and LOI may be good indicators of chemical weathering for the dacites. Geomechanical laboratory tests\r\nindicate that the strength of the samples is controlled by weathering. Field observations and mineralogical analyses show that the\r\neffects of weathering are critical for slope stability.
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