The Cerro Purico Shield Complex, North Chile
Cerro Purico is a 1.3 Ma 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 host. The youngest dome (Chascon) contains basaltic xenoliths characterized by Sr isotope ratios (0.7059) lower than the host dacite (0.7073). While the major and trace element chemistry of the suite is unexceptional, 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.
KeywordsMagma Chamber Basaltic Magma Pumice Clast Bishop Tuff Trace Element Chemistry
Unable to display preview. Download preview PDF.