 Calabozos lies between two different types of volcanism — to its north , andesite and rhyolite are the primary constituents of lava while its southern neighbors are composed of more mafic andesite and basalt . It is mainly basaltic andesite and rhyodacite that make up Calabozos , forming a calcalkilic suite rich with potassium . Its lavas are dotted with phenocrysts , which vary from 2 to 25 percent of their mass . These phenocrysts are typically made of plagioclase , but also contain clinopyroxene , orthopyroxene , ilmenite , apatite , and titanomagnetite . 
