1964/01/01 by I. S. E. Carmichael · 8 citations
Earth and Planetary Sciences · Environmental Science · #Geology and Paleoclimatology Research #Methane Hydrates and Related Phenomena #Geological and Geochemical Analysis
paper · doi:10.1093/petrology/5.3.435
openalex publication_date 1964/01/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
The Tertiary flood-basalt sequence of eastern Iceland is intermittently disturbed by central volcanic activity with the voluminous eruption of acid magma. Associated with one of these central volcanoes, described in this paper, is an intense swarm of acid and basic dykes, a set of acid cone-sheets, and extensive superimposed hydrothermal alteration. The lavas and intrusions which make up the volcano grade in composition from olivine-tholeiites, through olivine-free tholeiites, basaltic-andesites, and andesites (icelandites), to rhyolites. This series is unusually rich in iron, titanium, and manganese, and poor in magnesium; alumina and total alkalis also tend to be low in the basic members. Magnetite (sensu lato) plays a varied role in the order of crystallization, and it is only in the intermediate stages of this fractionated series that magnetite is available for crystal fractionation. The otherwise progressive enrichment of iron relative to magnesium throughout the successive liquids of the series is halted during an intermediate stage, as magnetite becomes an early-crystallizing phase.