0000000000311329
AUTHOR
Ray Macdonald
Evolution of the magma system of Pantelleria (Italy) from 190 ka to present
The eruptive history of Pantelleria has been marked by the eruption of nine peralkaline ignimbrites, with inter-ignimbrite episodes from small, local volcanic centres. New whole-rock geochemical data are presented for seven ignimbrites and used with published data for younger units to track compositional changes with time. From»190 ka, silicicmagmatismwas dominated by comenditic trachyte to comendite compositions, evolving along generally similar liquid lines of descent (LLOD). The final ignimbrite, the Green Tuff (»46 ka), was tapped from a compositionally zoned pantelleritic upper reservoir to a trachytic mush zone. Younger (20–7 ka) silicic magmatism has been relatively small scale, with…
Phase equilibrium constraints on the production and storage of peralkaline silicic magmas: insights from Kenya and Pantelleria.
The origin of peralkaline silicic rocks is still obscure and stands perhaps as one of the last major unsettled issues in classic igneous petrology. The debate goes back to the end of the 18th century and despite intensive petrological, geochemical and laboratory efforts the consensus has yet to emerge as to which mechanisms produce peralkaline derivatives. Bowen (1937) first proposed that the shift from metaluminous to peralkaline field was due to extensive fractionation of calcic plagioclase. Perhaps the best illustration of such an hypothesis is provided by the Boina rock series in the Ethiopian rift studied by Barberi et al. (1975). However, such an hypothesis still awaits experimental c…