Multi-stage evolution of the picritic M�lifell rocks, SW Iceland: constraints from mineralogy and inclusions of glass and fluid in olivine

Hansteen, Thor

doi:10.1007/bf00306481

Cited by 40 publications

(20 citation statements)

References 57 publications

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“…Phenocryst assemblage. inferred sequence of phenocryst crystallization (olivine À olivine + plagioclase À olivine + plagioclase + clinopyroxene), and low-CO 2 olivine-hosted melt inclusions (Hansteen, 1991) suggest shallow, 1-2 kbars, preeruptive storage before eruption (Bell and Humphries, 1972;Metrich et al, 1991).…”

Section: Deep or Shallow Magma Chamber To Explain Largevolume Low-d 1mentioning

confidence: 97%

Oxygen isotope heterogeneity and disequilibria of olivine crystals in large volume Holocene basalts from Iceland: Evidence for magmatic digestion and erosion of Pleistocene hyaloclastites

Bindeman

Gurenko

Sigmarsson

et al. 2008

Geochimica et Cosmochimica Acta

114

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Section: Deep or Shallow Magma Chamber To Explain Largevolume Low-d 1mentioning

confidence: 97%

Oxygen isotope heterogeneity and disequilibria of olivine crystals in large volume Holocene basalts from Iceland: Evidence for magmatic digestion and erosion of Pleistocene hyaloclastites

Bindeman

Gurenko

Sigmarsson

et al. 2008

Geochimica et Cosmochimica Acta

114

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“…The three samples from Iceland (Mid-P, Mid-2, KBS-1) represent Hardardottir (1986), Tronnes (1990) and Hansteen (1991). The F2 samples (F2-1, F2-2) are dredged samples of a pillow margin quenched by seawater from just west of the East Pacific Rise.…”

Section: Samples and Techniquesmentioning

confidence: 99%

Growth Forms and Composition of Chromian Spinel in Morb Magma: Diffusion-Controlled Crystallization of Chromian Spinel

Roeder

Poustovetov

Öskarsson

2001

The Canadian Mineralogist

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Microphenocrysts of chromian spinel in glass from an East Pacific Rise lava and three Icelandic subglacial lavas show a variety of complex skeletal, hopper, vermiform and chain textures. These grains of chromian spinel are larger than those found in most basalts. Many crystals show significant zoning in Cr/(Cr + Al), and the variation in Cr/(Cr + Al) with respect to Fe 2+ /(Fe 2+ + Mg) is distinctive for each sample. The four samples are relatively primitive, with between 9 and 10 wt.% MgO in the glass. One very distinctive texture, a core surrounded by a vermiform rim, has been interpreted by a number of researchers as a reaction texture caused either by changes in pressure or magma mixing. The variety of chromian spinel textures, including the vermiform rim, has been duplicated in an experimental run using the sample from the East Pacific Rise. The sample was held at 1225°C for 67 hours and then cooled slowly over 8 hours to 1147°C. We conclude that the vermiform texture and the other chromian spinel textures in the experimental run and the lavas are growth textures and not reaction textures. The change in growth habit that produces the vermiform rim is interpreted as diffusion-controlled growth, leading to what metallurgists refer to as cellular growth. Chromian spinel is susceptible to diffusion-controlled growth because of the very large difference in concentration of Cr in the melt (0.02-0.06 wt.% Cr 2 O 3 ) and in chromian spinel (30-50 wt.% Cr 2 O 3 ) at equilibrium. Although the chromian spinel in the glass of each natural sample shows a large variation in Cr/(Cr + Al), and thus was not in equilibrium with the bulk melt, its Fe 2+ / (Fe 2+ + Mg) may have been close to equilibrium with the bulk melt before quenching. The chromian spinel crystallized over a span of hours to days before a rapid water quench upon eruption. The complex textures and zoning probably reflect the turbulent conditions during passage of the magma toward the Earth's surface.Keywords: chromian spinel, chromite, basalt, texture, vermiform, hopper, diffusion-controlled crystallization. SOMMAIREDes microphénocristaux de spinelle chromifère sont présents dans une matrice vitreuse d'une lave basaltique provenant de la ride Est-Pacifique et de trois échantillons de coulées mises en place sous un glacier en Icelande. Ces cristaux contiennent une variété de textures complexes en entonnoir, vermiformes et en chaînes; ils sont plus grossiers que ceux qui caractérisent la plupart des basaltes. Plusieurs cristaux montrent une zonation importante en Cr/(Cr + Al), qui varie de façon distincte avec Fe 2+ /(Fe 2+ + Mg) dans chaque échantillon. Les quatre échantillons sont relativement primitifs, le verre contenant entre 9 et 10% (poids) de MgO. On a généralement interprété la présence d'un coeur entouré d'un liseré vermiforme comme résultat d'une réaction suite à des changements en pression ou à un mélange de magmas. La diversité texturale du spinelle chromifère, y inclus la bordure vermiforme, a été reproduite dans un série d'expériences f...

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“…This technique has been used previously to homogenize inclusions in phenocrysts (Vicenzi, 1985; Hansteen, 1991;Coombs et al, 1991;Sinton et al, 1993). The temperature was controlled to within 2°C of the indicated temperature using a Deltec vertical quench furnace, Eurotherm temperature controllers, and Pt-PtlO%Rh thermocouples.…”

Section: High Temperature Microthermometrymentioning

confidence: 99%

Geochemical Characteristics of Refractory Silicate Melt Inclusions from Leg 140 Diabases

Johnson¹,

Fisk²,

Naslund³

1995

Proceedings of the Ocean Drilling Program, 137/140 Scientific Results

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Geochemical data from plagioclase-hosted silicate melt inclusions from Leg 140, Hole 504B diabase dikes are reported. Hand-picked plagioclase grains were heated to 1260°-1280°C to remelt the glass inclusions and to infer trapping temperatures. The samples were then polished to expose the inclusions, which were analyzed by electron and ion microprobes. Inclusion compositions are mainly in equilibrium with the host plagioclase and are more depleted in incompatible elements than the host rock. Simple crystal-liquid equilibrium calculations show that the melt inclusions could have been in equilibrium with depleted abyssal peridotite diopsides, whereas whole-rock basalt compositions generally could not have been. The melt inclusions are significantly more depleted than normal (N-type) mid-ocean-ridge basalt (MORB) and are consistent with being produced by 8%-16% incremental or open-system melting with 2% residual porosity in the peridotite source. These magmas were formed during pressurerelease melting of the mantle over a range of depths between 30 and 15 km.

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Multi-stage evolution of the picritic M�lifell rocks, SW Iceland: constraints from mineralogy and inclusions of glass and fluid in olivine

Cited by 40 publications

References 57 publications

Oxygen isotope heterogeneity and disequilibria of olivine crystals in large volume Holocene basalts from Iceland: Evidence for magmatic digestion and erosion of Pleistocene hyaloclastites

Oxygen isotope heterogeneity and disequilibria of olivine crystals in large volume Holocene basalts from Iceland: Evidence for magmatic digestion and erosion of Pleistocene hyaloclastites

Growth Forms and Composition of Chromian Spinel in Morb Magma: Diffusion-Controlled Crystallization of Chromian Spinel

Geochemical Characteristics of Refractory Silicate Melt Inclusions from Leg 140 Diabases

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