Abstract
In this study, the geological, petrographical properties of rhyolitic tuffs exposed around ?an-Etili in the Biga Peninsula (NW Turkey) which are pyroclastic products of Late Oligocene-Early Miocene aged ?an Volcanism were investigated, also physical and mechanical characteristics of tuffs introduced and tried to determine the impact on engineering properties of petrographical features. In the region, rhyolitic tuffs called locally “?an stone” have been used as covering and building stones for many years. These tuffs generally have light yellowish, beige, brown colored and different patterns with light yellowish, cream, reddish and brown colors caused by iron oxidation of hydrothermal alteration. They are preferred as coatings and decorative stone with these patterns. ?an stone which consisted of rhyolitic composition, lithic and locally crystalline tuffs has compact structure. The mineral assemblage of tuffs is mainly composed of quartz, plagioclase, rarely biotite, amphibole (hornblende) phenocrystals and opaque mineral with particles of volcanic glass and lithic fragments. Not only petrographical and geochemical analyses were carried out but also standard rock mechanic tests (unit weight, specific gravity, porosity, water absorption and uniaxial compressive strength) on rhyolitic tuffs samples collected from four different quarries (Hoppa Hill, Halilaga, Uzunalan, Dereoba). Simple regression analysis of test results obtained from four different regions and correlations were found good correlation between engineering proper- ties and the petrographical and chemical properties of rhyolitic tuffs.
Highlights
Biga Peninsula of northwestern Turkey is associated with widespread magmatism which developed in different stage and different characters from Late Eocene to Pliocene
Specimens of 20 × 20 × 20 cm dimensions were taken from the quarries in 4 different areas (namely Hoppa Hill (1), Halilağa(2), Uzunalan(3), Dereoba(4)—Figure 1) where Çan stone were processed and subjected to standard rock mechanic experiments such as uniaxial compressive strength, unit weight, specific gravity, porosity and water absorption
Detailed geological studies conducted in the area and tuffs found in a vast area in the south of Çan-Etili constitute the pyroclastic last products of volcanism developed in the area
Summary
The geochemical characteristics of these rocks are defined by high-K calc-alkaline magmatism series which are abundant of basalt, andesite and trachyandesite, latite, dacite, rhylolite and they involve rocks with their pyroclastic associations [3,5,10]. Following to this magmatic activity the subsequent stages of magmatic rocks are associated with extensional tectonic regime, because the large scale plate deformation is dominated by extension at the Middle-Late Miocene [6,11,12]. Rhyolitic tuffs of Çan volcanism in this study is the first time in its effects on engineering properties of petrographic characteristics were investigated
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