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Origin of fine-grained granular rocks in layered intrusions

Published online by Cambridge University Press:  01 May 2009

P. Thy  and
K. H. Esbensen
P. Thy
Affiliation:
Nordic Volcanological InstituteUniversity of Iceland101 ReykjavikIceland
K. H. Esbensen
Affiliation:
Department of MetallurgyTechnical University of DenmarkBuilding 2042800 LyngbyDenmark
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Summary

Extremely fine-grained granular rocks are found interleaved with cumulates in some layered differentiated intrusions. The question arises as to whether these can be interpreted as chilled magmas. If this were so it would allow the liquid line of descent to be determined directly. A study of extremely fine-grained granular rocks in the differentiated, layered basic Fongen–Hyllingen complex, Norway, however, showed rocks of this type to be cumulates. Fluctuations in volatile pressure due to crystallization of a hydrous phase may give rise to modal and grain-size variation in layered intrusions.

Type
Articles
Information
Geological Magazine , Volume 119 , Issue 4 , July 1982 , pp. 405 - 412
Copyright
Copyright © Cambridge University Press 1982

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