1990/04/01 by D. W. McGARVIE, Dave McGarvie, Robie W. Macdonald +5 · 70 citations
Earth and Planetary Sciences · #Basalt #Geochemistry #Geological and Geochemical Analysis #Geology #Geology and Paleoclimatology Research #Geomorphology #Igneous differentiation #Magma #Magma chamber #Magmatism #Paleontology and Stratigraphy of Fossils #Peralkaline rock #Petrology #Rhyolite #Rift #Seismology #Structural basin #Volcanic rock #Volcano
paper · doi:10.1093/petrology/31.2.461
published in Journal of Petrology 31(2), 461-481 (Oxford University Press)
openalex publication_date 1990/04/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/27
In southern Iceland, tholeiitic basalt magmas propagating laterally from the active Eastern Rift Zone into the older cmstal segment of the South Eastern Zone have been injected into Torfajökull, a mature volcanic centre dominated by rhyolites. Eruptions of complex suites of mixed and hybrid rocks have been triggered, involving tholeiites of the rift zone and transitional basalts and rhyolites of the Torfajökull centre. Three-component hybrids are an unusual feature of the activity. The distribution of various magma mixing and hybrid types is related to the periodic injection of tholeiite into a magma chamber, or chambers, where rhyolite overlies parental transitional basalts. Pre-postglacial rhyolites (>10000 y) at Torfajokull are predominantly peralkaline, whereas later rhyolites are, with few exceptions, subalkaline. Furthermore, the injection of rift zone magmas, and the consequent abundance of rhyolite-basalt mixing, have been important features of magmatism at the centre only in postglacial times. Reduced repose times in the magma reservoirs have prevented the production of peralkaline rhyolites. These trends are interpreted in terms of the southerly migration of the Eastern Rift Zone.