Element compositions match those of other volcanoes in the CVZ. Ollagüe magmas did not exclusively form from fractional crystallization; magma mixing and crustal contamination contributed to the formation of the magmas although it is not easy to determine what the composition of contaminants was. Probably, it was in part hydrothermally altered upper crustal rock, and in part Miocene age ignimbrites that crop out close to the volcano in Bolivia. Crystal fractionation with some minor contamination by crustal components is probably the most satisfactory explanation for the magma chemistry of Ollagüe. It is however difficult to tell the relative importance of contamination vs. assimilation.