dc.contributor.author Holness, Marian B dc.contributor.author Fowler, AC dc.date.accessioned 2022-06-07T15:00:56Z dc.date.available 2022-06-07T15:00:56Z dc.date.issued 2022-06 dc.date.submitted 2021-08-03 dc.identifier.issn 0010-7999 dc.identifier.other s00410-022-01921-w dc.identifier.other 1921 dc.identifier.uri https://www.repository.cam.ac.uk/handle/1810/337875 dc.description.abstract AbstractWe provide a simple geometric theory of crystal growth which predicts the shape and final dihedral angle of three-grain junctions of an augite crystal with two plagioclase grains. The predicted dihedral angle $$\Delta$$ Δ depends on the initial impingement angle $$\psi$$ ψ formed by the plagioclase grains, and also on the relative growth rates of the augite and the plagioclase, and shows reasonable agreement with data obtained from natural samples. We show that the two augite-plagioclase grain boundaries will normally curve towards each other, which is consistent with the first two types of junction described in the companion paper. However, the third type, the eagle’s beak, is formed by the meeting of grain boundaries which curve in the same direction. Although it is possible to account for this type of junction by invoking the localised dissolution of one of the plagioclase grains, this is unlikely to occur. A more plausible explanation involves the late impingement of the two plagioclase grains, consistent with the observation that eagles’ beaks are common in gabbros and strongly orthocumulate troctolites, in which the plagioclase framework has not been established by the time augite is growing in substantial quantities. An observed flattening of the curve of $$\Delta$$ Δ values at high values of $$\psi$$ ψ can be explained by taking into account the importance of interfacial energy in late-stage crystallisation. dc.language en dc.publisher Springer Science and Business Media LLC dc.subject Original Paper dc.subject Magma crystallisation dc.subject Dihedral angle dc.subject Melt-back dc.title The formation of three-grain junctions during solidification. Part II: theory dc.type Article dc.date.updated 2022-06-07T15:00:56Z prism.issueIdentifier 6 prism.publicationName CONTRIBUTIONS TO MINERALOGY AND PETROLOGY prism.volume 177 dc.identifier.doi 10.17863/CAM.85281 dcterms.dateAccepted 2022-04-15 rioxxterms.versionofrecord 10.1007/s00410-022-01921-w rioxxterms.version VoR rioxxterms.licenseref.uri http://creativecommons.org/licenses/by/4.0/ dc.contributor.orcid Fowler, A. C. [0000-0002-2062-6372] dc.identifier.eissn 1432-0967 pubs.funder-project-id natural environment research council (NE/N009894/1) pubs.funder-project-id engineering and physical sciences research council (EP/K032208/1) pubs.funder-project-id science foundation ireland (12/IA/1683) cam.issuedOnline 2022-06-07
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