ABSTRACT:  Tertiary basic volcanic« which, crop out -over an. area of `9000 kim^ `between Manisa and Balıkesir` are divided in to fivedifferent eruptional phases and. the results of petrochemical analyses and genetic interpretations are given.. Some of the rock,,,, appearing as alkali basalts in the field are. evaluated to be quartz latite .and andésite and named as "Pseudo-basalts** through geochemical data and pétrographie observations. Those pseudo-basalts, which, form a special volcanic group in Western Anatolia are. believed to have, a crustlcmantle origin. The hybrid magma which is the mix.tu.re of the crust and the mantle was formed the pseudo-basalts from Upper Oligocène. The pseudo-basalts acquire a characteristic alkali basalt composition from. Pliocene onwards due to progressive, decrease of the crustal material. Former investigatiois which have worked in the area described as "basalts`* and named some fonmations on, those volcanic rocks. It is necessary that new researches must, be made and the names of `the formations must, be corrected