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Laboratory duplication of comb layering in the Rhum plutonA description is provided of the texture of harrisite comb layers, taking into account the results of crystallization experiments at controlled cooling rates, which have reproduced the textural change from 'cumulate' to comb-layered harrisite. Melted samples of harrisite were used in the dynamic crystallization experiments considered. The differentiation of a cooling rate run with respect to olivine grain size and shape is shown and three possible origins of hopper olivine in differentiated crystallization runs are considered. It is found that olivine nucleation occurred throughout cooling, except for the incubation period during early cooling. The elongate combed olivines in harrisite apparently grew as the magma locally supercooled to at least 30 C. It is suggested that the branching crystals in most comb layers, including comb-layered harrisite, probably grew along thermal gradients.
Document ID
19780049091
Document Type
Reprint (Version printed in journal)
Authors
Donaldson, C. H.
Date Acquired
August 9, 2013
Publication Date
September 1, 1977
Publication Information
Publication: Mineralogical Magazine
Volume: 41
Subject Category
EARTH RESOURCES AND REMOTE SENSING
Funding Number(s)
CONTRACT_GRANT: NSR-09-051-001
Distribution Limits
Public
Copyright
Other