Layering in the Gars-bheinn ultrabasic sill, Isle of Skye: a new interpretation, and its implications

Bevan, J. C.; Hutchison, Robert

doi:10.1144/sjg20030329

Cited by 4 publications

(1 citation statement)

References 10 publications

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“…However, Hutchison (1966) pointed out that clouding within gabbros of the Cuillin Igneous Complex is not a rare feature, and is to be found in units which clearly post-date the ultrabasic rocks. A relative age for the GBG was determined by Bevan and Hutchison (1984), based on the presence of peridotite xenoliths veined with gabbro, within (tentatively identified) GBG north of Eilean Reamhar on the shore of Loch na Cuilce (Fig. 1).…”

Section: Units Of the Cuillin Igneous Complex Predating The Ultrabasimentioning

confidence: 99%

The structure and petrology of ultrabasic rocks in the southern part of the Cuillin Igneous Complex, Isle of Skye

Claydon¹,

Bell²

1992

Transactions of the Royal Society of Edinburgh: Earth Sciences

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The ultrabasic rocks of the southern portion of the Early Tertiary Cuillin Igneous Complex, Isle of Skye, are recognised as forming a Peridotite Series s.l. and have been separated into six distinct structural–lithological units. These units range from almost pure dunite (Unit 1, at the lowest structural level), through to feldspathic peridotites and allivalites (Units 5 and 6, at the highest structural levels). Detailed field and mineralogical studies indicate that both cumulus and postcumulus processes involving ultrabasic (picritic) magmas may be identified, and that the latter processes have significantly modified many of the primary features of these rocks.Layering, both modal and phase, is present within all six units, although it is more prominent within the higher units, especially Units 5 and 6. Differing orientations of fabrics defined by cumulus spinel and intercumulus plagioclase layers within Unit 3 indicate the important role of compaction and intercumulus melt migration. Unit 4 is extremely heterogeneous, involving material ranging in composition from peridotite to allivalite, and provides clear evidence for postcumulus melt movement, magma-mixing, disruption and brecciation. Units 5 and 6 developed with a more porous cumulus framework, giving rise to dendritic growths involving cumulus olivine and poikilitic plagioclase.It is concluded that postcumulus melt movement, injection and magma-mixing, involving ultrabasic magmas, were significant processes in the formation of the ultrabasic rocks of the Cuillin Igneous Complex.

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Section: Units Of the Cuillin Igneous Complex Predating The Ultrabasimentioning

confidence: 99%

The structure and petrology of ultrabasic rocks in the southern part of the Cuillin Igneous Complex, Isle of Skye

Claydon¹,

Bell²

1992

Transactions of the Royal Society of Edinburgh: Earth Sciences

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Mechanisms of Formation of Igneous Layering

Naslund

McBirney

1996

Developments in Petrology

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Magnetic polarity stratigraphy of the Tertiary igneous rocks of Skye, Scotland

Dagley

Mussett

Skelhorn

1990

Geophysical Journal International

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S U M M A R Y Palaeomagnetic results are given for 115 sites, mainly from the central igneous intrusive complex, and also radiometric dates by the 40Ar-39Ar step-heating method. These are combined with published dates and palaeomagnetic results for the lavas and regional dyke swarms with the aim of establishing the magnetic polarity stratigiaphy.Igneous activity spanned at least the approximate interval 61-54 Ma, and a polarity sequence of at last R-N-R-N-R, but could span seven polarity intervals, R-N-R-N-R-N-R, depending on the age of the Loch Ainort Epigranite. However, these polarities cannot be identified with specific chrons of either the Harland et al. (1982) or Berggren et al. (1985) polarity time-scales.The Skye igneous activity, therefore, spans more polarity intervals than in Mull, Ardnamurchan or Rhum and this is consistent with the radiometric ages.Interpretations of the results for the Coke Uaigneich and related granites and for the Loch Ainort Epigranite present problems, and partial solutions are offered.

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Layering in the Gars-bheinn ultrabasic sill, Isle of Skye: a new interpretation, and its implications

Cited by 4 publications

References 10 publications

The structure and petrology of ultrabasic rocks in the southern part of the Cuillin Igneous Complex, Isle of Skye

The structure and petrology of ultrabasic rocks in the southern part of the Cuillin Igneous Complex, Isle of Skye

Mechanisms of Formation of Igneous Layering

Magnetic polarity stratigraphy of the Tertiary igneous rocks of Skye, Scotland

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