Akademik Veri Yönetim Sistemi
ARABIAN JOURNAL OF GEOSCIENCES, cilt.14, sa.12, 2021 (SCI-Expanded)
This study reveals the petrographic and geochemical characteristics, physico-mechanical properties, and chemical alteration indices of Hisartepe volcanic rocks with basaltic andesite, trachyandesite, and andesite composition. Although all rocks have common groundmass plagioclase microlites, the porphyritic texture is majorly evident except for aphyric Asartepe samples. Phenocryst rates vary by location, and vesicle rates are around the maximum of 5%. The chemical alteration indices used to determine the degree of alteration of rocks are in a narrow range and indicate a weak and limited alteration. Plagioclase index of alteration (PIA) and sericitization index (SI) imply the alteration degree of plagioclase mineral abundance in most study area rocks. According to these indices, the most altered rocks in the study area are in the NE Davutlar and Hisartepe regions. Petrographic determination and XRD analysis of rocks verify these results. The rocks of the study area yielded uniaxial compressive strength (UCS) varying between 36.80 and 87.40 MPa classified as low and medium strength. Bohme abrasion of the study area rocks changes from 6.90 to 12.65 cm(3)/50 cm(2) and increases with the degree of alteration and loss on ignition (LOI). The USC and point load strength values increase with the decrease in phenocryst sizes and ratios. The different results seen in the chemical alteration indices of volcanic rock samples taken from different locations are due to the modal mineralogy in rocks. Petrographic characteristics such as the phenocryst ratio and phenocryst size along with the alteration affect the mechanical properties of the volcanic rocks. As a result, the Sivritepe and Asartepe samples are the best samples in terms of engineering properties.