Mafic tholeiitic basalts from the Nejapa and Granada (NG) cinder cone alignments provide new insights into the origin and evolution of magmas at convergent plate margins. In comparison to other basalts from the Central American volcanic front, these marie tholeiitic basalts are high in MgO and CaO and low in Al2Op, K2O1, Ba and Sr. They also differ from other Central American basalts, in having clinopyroxene phenocrysts with higher MgO, CaO and Cr2O3 concentrations and olivine phenocrysts with higher MgO contents. Except for significantly higher concentrations of Ba, Sr and