Cerro Purico is a 1.3 m.y.-old ignimbrite shield volcano. The first erupted unit was the rhyolitic Toconao ignimbrite (87Sr/86Sr 0.7100), followed, after an erosional interval, by the dacitic Purico ignimbrite with the same radiometric age (87Sr/86Sr 0.7085). Andesitic to dacitic lavas and extrusive domes were later emplaced in the summit region. The upper part of the Purico ignimbrite contains banded and mafic (andesitic) pumices isotopically indistinguishable from the hosts. The younger dome (Chascon) contains basaltic xenoliths characterized by Sr isotope ratios (0.7059) lower than the host dacite (0.7073). The rocks of the Cerro Purico complex as a whole are characterized as low TiO2, high K, calc-alkaline types with major and trace-element contents closely similar to other Central Andean volcanoes. A complex magmatic history is required to explain the origin of mafic pumice clasts and isotopically contrasted mafic xenoliths. Simple crustal anatexis cannot account for the range of compositions observed.-J.M.H.
ASJC Scopus subject areas
- Environmental Science(all)
- Earth and Planetary Sciences(all)