Spherulitic textures formed during crystallization of partially melted arkose, Rum, Scotland

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doi: 10.1017/S0016756802006842
Authors:Holnes, Marian B.
Author Affiliations:Primary:
University of Cambridge, Department of Earth Sciences, Cambridge, United Kingdom
Volume Title:Geological Magazine
Source:Geological Magazine, 139(6), p.651-663. Publisher: Cambridge University Press, London, United Kingdom. ISSN: 0016-7568
Publication Date:2002
Note:In English. 15 refs.; illus., incl. 2 tables, geol. sketch map
Summary:Melting of Torridonian arkoses, due to intrusion of shallow bodies of mafic melts on the Island of Rum, was locally extensive, reaching up to 95 vol.%. Crystallization (to form granophyre) of these highly melted rocks was generally static in the vicinity of minor intrusions, although disruption of bedding is apparent in the aureole of the main mafic pluton. A distinctive mm-cm-scale spherulitic texture developed during solidification of the partially melted arkoses, in the aureole of the main intrusion, and in those of associated minor gabbro plugs. The spherulites are formed of radiating, fan-shaped intergrowths of plagioclase and quartz set in a matrix of quartz, plagioclase and K-feldspar. The importance of nucleation rates in determining texture development is demonstrated by a dominance of Na-rich compositions in the first feldspar to form, even in non-spherulitic rocks. It is suggested that the spherulites formed by the early growth of metastable plagioclase due to difficulties in nucleating feldspar. [G.L.B.]
Subsections:Metamorphism: thermal, metasomatic
Subjects:Arkose; Chemical composition; Clastic rocks; Crystallization; Equilibrium; Mineral composition; Neoproterozoic; Partial melting; Petrography; Petrology; Precambrian; Proterozoic; Sedimentary rocks; Spherulites; Textures; Torridonian; Upper Precambrian; Europe; Great Britain; Hebrides; Highland region Scotland; Inner Hebrides; Inverness-shire Scotland; Rhum; Scotland; United Kingdom; Western Europe
Coordinates:N565500 N570500 W0061500 W0063000
Abstract Numbers:03M/3345
Record ID:2003027702
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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