Contact metamorphism and anatexis of Torridonian arkose by minor intrusions of the Rum igneous complex, Inner Hebrides, Scotland

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doi: 10.1017/S0016756899002988
Authors:Holness, M. B.
Author Affiliations:Primary:
University of Cambridge, Department of Earth Sciences, Cambridge, United Kingdom
Volume Title:Geological Magazine
Source:Geological Magazine, 136(5), p.527-542. Publisher: Cambridge University Press, London, United Kingdom. ISSN: 0016-7568
Publication Date:1999
Note:In English. 15 refs.; illus., incl. 4 tables, geol. sketch maps
Summary:Large volumes of partial melt were produced in the arkosic contact aureoles of two of the numerous mafic-ultramafic minor intrusions in the N of Rum. Melting was static, with little movement of melt even on a thin-section scale, and no segregation. The relative proportions of (now inverted) tridymite and high quartz, which crystallized in the silica primary-phase field, constrain the P of metamorphism to 150 ± 50 bar; 95 vol.% melting occurred ≤ 15 m from the contact with the 50 m diameter gabbro plug, whereas ∼ 70 vol.% melting occurred ≤ 6 m around the adjacent 200 m diameter peridotite plug. Simple thermal models of the aureoles, the breakdown of chlorite and the disordering of microcline, support the hypothesis that the peridotite plug was injected as a crystal-rich mush close to its solidus, whilst the gabbro plug was a long-lived feeder conduit. Time scales for the melting events are ∼ 40 y for the gabbro-, and 10 y for the peridotite aureole. Crystallization, which was rapid, taking 10 y for the gabbro and 4 for the peridotite, produced a fine-grained cotectic intergrowth, and preserved melt distribution. [J.F.]
Sections:Petrology
Subsections:Metamorphism: thermal, metasomatic
Subjects:Anatexis; Arkose; Chemical composition; Clastic rocks; Contact metamorphism; Crystallization; Intrusions; Metamorphism; Neoproterozoic; Partial melting; Precambrian; Proterozoic; Sedimentary rocks; Torridonian; Upper Precambrian; Europe; Great Britain; Hebrides; Inner Hebrides; Scotland; United Kingdom; Western Europe; Rum Complex
Abstract Numbers:00M/2188
Record ID:2000004689
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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100 1 |a Holness, M. B.  |e analytic author  |u University of Cambridge, Department of Earth Sciences, Cambridge 
245 1 0 |a Contact metamorphism and anatexis of Torridonian arkose by minor intrusions of the Rum igneous complex, Inner Hebrides, Scotland 
300 |a p. 527-542 
500 |a In English. 15 refs. 
500 |a Abstract number: 00M/2188 
500 |a Abstractor: J.F. 
500 |a Category Section: Petrology 
500 |a Category Subsection: Metamorphism: thermal, metasomatic 
500 |a Affiliation: University of Cambridge, Department of Earth Sciences; Cambridge; GBR; United Kingdom 
500 |a Key title: Geological Magazine 
500 |a Source note: Geological Magazine, 136(5), p.527-542. Publisher: Cambridge University Press, London, United Kingdom. ISSN: 0016-7568 
500 |a Publication type: journal article 
504 |b 15 refs. 
510 3 |a GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom 
520 |a Large volumes of partial melt were produced in the arkosic contact aureoles of two of the numerous mafic-ultramafic minor intrusions in the N of Rum. Melting was static, with little movement of melt even on a thin-section scale, and no segregation. The relative proportions of (now inverted) tridymite and high quartz, which crystallized in the silica primary-phase field, constrain the P of metamorphism to 150 ± 50 bar; 95 vol.% melting occurred ≤ 15 m from the contact with the 50 m diameter gabbro plug, whereas ∼ 70 vol.% melting occurred ≤ 6 m around the adjacent 200 m diameter peridotite plug. Simple thermal models of the aureoles, the breakdown of chlorite and the disordering of microcline, support the hypothesis that the peridotite plug was injected as a crystal-rich mush close to its solidus, whilst the gabbro plug was a long-lived feeder conduit. Time scales for the melting events are ∼ 40 y for the gabbro-, and 10 y for the peridotite aureole. Crystallization, which was rapid, taking 10 y for the gabbro and 4 for the peridotite, produced a fine-grained cotectic intergrowth, and preserved melt distribution. 
650 7 |a Anatexis  |2 georeft 
650 7 |a Arkose  |2 georeft 
650 7 |a Chemical composition  |2 georeft 
650 7 |a Clastic rocks  |2 georeft 
650 7 |a Contact metamorphism  |2 georeft 
650 7 |a Crystallization  |2 georeft 
650 7 |a Intrusions  |2 georeft 
650 7 |a Metamorphism  |2 georeft 
650 7 |a Neoproterozoic  |2 georeft 
650 7 |a Partial melting  |2 georeft 
650 7 |a Precambrian  |2 georeft 
650 7 |a Proterozoic  |2 georeft 
650 7 |a Sedimentary rocks  |2 georeft 
650 7 |a Torridonian  |2 georeft 
650 7 |a Upper Precambrian  |2 georeft 
651 7 |a Europe  |2 georeft 
651 7 |a Great Britain  |2 georeft 
651 7 |a Hebrides  |2 georeft 
651 7 |a Inner Hebrides  |2 georeft 
651 7 |a Scotland  |2 georeft 
651 7 |a United Kingdom  |2 georeft 
651 7 |a Western Europe  |2 georeft 
653 |a Rum Complex 
773 0 |t Geological Magazine  |d London : Cambridge University Press, Sep. 1999  |x 0016-7568  |y GEMGA4  |n Geological Magazine, 136(5), p.527-542. Publisher: Cambridge University Press, London, United Kingdom. ISSN: 0016-7568 Publication type: journal article  |g Vol. 136, no. 5  |h illus., incl. 4 tables, geol. sketch maps 
856 |u urn:doi: 10.1017/S0016756899002988