logo
Normal view MARC view ISBD view

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

By: Holness, M.B.
Material type: ArticleArticleDescription: 651-663p ; Illustration.Subject(s): crystallization - Melted arkose - Rum - Scotland | Petrology - Rum - Scotland In: Geological magazine : Vol. 139 Iss. 1-6 Year. 2002Summary: Abstract Melting of Torridonian arkoses, due to intrusion of shallow bodies of mafic melts on the Isle 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 millimetre- to centimetre-scale spherulitic texture developed during solidification of the partially melted arkose, in both the aureole of the main intrusion, and also 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.
Tags from this library: No tags from this library for this title. Log in to add tags.
    Average rating: 0.0 (0 votes)
Item type Current location Collection Call number Status Date due Barcode
Article Article Library and Information Centre
Periodical Section
Bound Journal Collection Not for loan 002519_87
Serials/Scientific Journal Serials/Scientific Journal Library and Information Centre
Periodical Section
Bound Journal Collection 550 GEO (Browse shelf) Available 002519

Abstract
Melting of Torridonian arkoses, due to intrusion of shallow bodies of mafic melts on the Isle 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 millimetre- to centimetre-scale spherulitic texture developed during solidification of the partially melted arkose, in both the aureole of the main intrusion, and also 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.

There are no comments for this item.

Log in to your account to post a comment.

Copyright © 2019 Geological Survey & Mines Bureau. All Rights Reserved.

Developed in Association with Finco Technologies (Pvt) Ltd

Powered by Koha