Mineral Chemistry and Geochemistry of Volcanic Rocks in The North of Pasinler (Erzurum)

Abstract

In the north of Pasinler (Erzurum), Upper Miocene-Pliocene volcanic rocks crop out. These volcanites are composed of basaltic andesite, andesite, dacite, rhyolite lavas and rhyolitic pyroclastics. The rocks show porphyritic, microlitic porphyritic, hyalo-microlitic porphyritic, vitrophyric, glomeroporphyritic, pilotaxitic and hyalopilitic textures. The investigated volcanites contain plagioclase (An29-80), olivine (Fo65-82), clinopyroxene (augite), orthopyroxene (enstatite), amphibole (Mg#: 0.57-0.71), biotite (phlogopite: 0.44-0.47, annite: 0.33-0.37), sanidine, quartz and opaque mineral (titano-magnetite and ilmenite). The volcanic rocks are calc-alkaline in character and have medium to high-K contents. Major oxide and trace element variations point out open-system magmatic differentiation in the evolution of rocks. Geochemical data indicate an important role of fractionation of phenocryst phases in the rocks during differentiation process. However, it is considered that assimilation±magma mixing might have accompanied to the process. High LILE (K, Rb, Ba, Th) and relatively low HFSE (Nb, Ta, Hf, Zr) contents of the rocks indicate that these rocks derived from parental magmas carrying subduction signature.

Keywords

• Pasinler, Mineral kimyası, Jeokimya, Kalkalkali volkanitler.