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Gravitational sorting of phenocrysts in some Icelandic intrusive sheets

Published online by Cambridge University Press:  01 May 2009

D. H. Blake
D. H. Blake
Affiliation:
Department of National Development, Bureau of Mineral Resources, Geology and Geophysics, Box 378, Canberra City, A.C.T., Australia.
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Summary

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.

Type
Articles
Information
Geological Magazine , Volume 105 , Issue 2 , April 1968 , pp. 140 - 148
Copyright
Copyright © Cambridge University Press 1968

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References

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