Journal ArticleDOI
Gravitational sorting of phenocrysts in some Icelandic intrusive sheets
TLDR
In this paper, the cross-section of a porphyritic central zone sharply bounded by non-porphyritic margins is described, where plagioclase, augite and olivine phenocrysts are arranged in two main layers.Abstract:
Some thin basaltic intrusive sheets in south-eastern Iceland consist in cross-section of a porphyritic central zone sharply bounded by non-porphyritic margins. Within the porphyritic zone phenocrysts of plagioclase, augite and olivine are arranged in two main layers, an upper layer containing mostly plagioclase phenocrysts, and a lower layer containing concentrations of augite and olivine phenocrysts. The phenocrysts are considered to have been gravitationally sorted during the passage through the sheets of a highly fluid and strongly flowing porphyritic basalt magma.read more
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Book ChapterDOI
Mechanisms of Formation of Igneous Layering
TL;DR: A wide variety of layer-forming mechanisms have been proposed in the literature, such as gravity settling, crystal sorting by magma currents, magmatic deformation, compaction, seismic shocks, or tectonic deformation as mentioned in this paper.
Journal ArticleDOI
Intrusive sheet swarms and the identity of Crustal Layer 3 in Iceland
TL;DR: In this article, a simple mechanism for the generation of the sheet swarm is proposed, based on the contrasted density gradients of crust and uprising magma: basic magma rises to the surface when its density is everywhere less than the bulk density of the rocks it cuts, otherwise it is often diverted laterally to form an intrusive sheet where its density equals that of the country rock.
Journal ArticleDOI
The mode of emplacement of Neogene flood basalts in Eastern Iceland: The plagioclase ultraphyric basalts in the Grænavatn group
Birgir V. Óskarsson,Christina B. Andersen,Morten S. Riishuus,Erik Vest Sørensen,Christian Tegner +4 more
TL;DR: In this article, the authors conduct detailed mapping of a PUB group in eastern Iceland, namely the Graenavatn group, and assess the group architecture, flow morphology and internal structure with additional constraints from petrography, petrology and crystal size distribution, to derive information on emplacement dynamics of plagioclase ultraphyric basalts.
Journal ArticleDOI
High pressure phases in Nigerian Cenozoic lavas distribution and geotectonic setting
TL;DR: Olivine nodules of the kind well known from alkaline basaltic associations all over the world, are widespread in Nigeria's Cenozoic volcanic province as discussed by the authors.
Volcanological studies of Neogene flood basalt groups in eastern Iceland
TL;DR: In this article, the authors investigated the mode of emplacement of flood basalts within six groups in the Neogene lava piles of eastern Iceland are subject to investigation, namely the Hólmar and Grjótá olivine basalt groups, the Kumlafell, Hölmatindur and Hjálmadalur groups (mostly tholeiitic) and the Grænavatn porphyritic basalt group (plagioclase ultraphyric basalt with macrocryst content ranging from 40-
References
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Journal ArticleDOI
Physical properties of erupting hawaiian magmas
TL;DR: In this article, field measurements and estimates of temperature, viscosity, gas content, and specific gravity of erupting Hawaiian lavas are assembled largely in tabular form, and they show that lava flows continue in motion to apparent temperatures less than 800°.
Journal ArticleDOI
The Net-Veined Complex of the Austurhorn Intrusion, Southeastern Iceland
TL;DR: The Austurhorn intrusion as discussed by the authors consists of a net-veined complex, in which acid, basic, and hybrid intermediate rocks are intimately associated, and it is concluded that the pillows represent intrusions of basic and hybrid magmas into acid magma.
Journal ArticleDOI
The Major Intrusions of South-Eastern Iceland
TL;DR: In the south-east of Iceland, the intrusions of plutonic habit in the country-rocks are mainly plateau-basalts of Tertiary age, with some rhyolitic lavas, tuffs, and breccias, having a north-westward to west-northwestward dip of 5° to 20° as mentioned in this paper.
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