The composition data indicate that Ollagüe was underpinned by a large magma chamber that was the source of the main edifice building andesite magmas. In this main magma chamber, differentiation processes generated the andesitic and dacitic magmas from basaltic andesite. The chamber itself was chemically zoned. Episodically, new mafic magmas were injected into the magma chamber from below. Subsidiary magma chambers which developed beneath the northwestern and southeastern flank gave rise to the La Celosa and Ch'aska Urqu volcanic centres, respectively. These subsidiary pathways also allowed basaltic andesite magmas to ascend to the surface; the main magma chamber would have intercepted any mafic magmas ascending into the central vent as such mafic magmas are denser. The walls of the magma chamber were also affected by strong hydrothermal alteration processes, with weaker alteration also occurring in the walls of the subsidiary magma chambers. La Poruñita was probably formed by magmas from the floor of the main magma chamber, or from the magma that enters the magma chamber from below; it had already undergone some crustal contamination in the depths of the crust when it erupted.