Türkiye Jeoloji Bülteni

Mineralogical - Petrographical and Geochemical Aspects of the Pazarcık Volcanics (Yıldızeli - Sivas)

Abstract: Volcanic rocks are common constituents of the post-collisional basins that developed after the collision of the Anatolideand Pontide microcontinents. These volcanic rocks (Pazarcık volcanics) are observed in the area around Yıldızeli. Pazarcıkvolcanics are composed ofbasltic and andesitic lava flows, and their pyroclastic equivalents. Basalts show hypocrystallineporphyritic-pilotaxitic texture, and include plagioclase, clinopyroxene and olivine phenocrysts. Andesites display hypocrystalline porphyritic texture, and include the hornblende and plagioclase phenocrysts.Major element data indicate that the Pazarcık volcanics are mainly calcalkaline, and partly alkaline in character. MORBnormalized spider diagram reveals that the Pazarcık volcanics are enriched in large ion lithophile (LIL) .elements and depleted in Ti and Y. Geotectonic discriminant diagram based on the trace element data implies that the Pazarcık volcanics havewithin-plate character.Considering the mineralogical-petrographical and geochemical data together with the regional geological setting, the following model may be suggested for the evolution of the Pazarcık volcanics: The magma was formed as a result of a smalldegree partial melting of the upper mantle peridotite under the tensional regime following the period of continental collisionbetween the Anatolide and Pontide fragments. During its ascent to the surface, this magma was contaminated by thickenedcontinental crust.