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The lithospheric mantle and lower crust-mantle relationships under Scotland: a xenolithic perspective

Upton, B.G.J. and Downes, Hilary and Kirstein, L.A. and Bonadiman, C. and Hill, P.G. and Ntaflos, T. (2011) The lithospheric mantle and lower crust-mantle relationships under Scotland: a xenolithic perspective. Journal of the Geological Society 168 (4), pp. 873-886. ISSN 0016-7649.

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Official URL: http://dx.doi.org/10.1144/0016-76492009-172

Abstract

In the British Isles the majority of volcanic rocks containing upper mantle and lower crustal xenoliths occur in Scotland. Most of the occurrences are of Carboniferous–Permian age. This paper presents new data on the mineral chemistry of spinel lherzolite xenoliths from the five principal Scottish tectonic terranes. Compositional variations among the minerals emphasize the broad lateral heterogeneity of the subcontinental lithospheric mantle across the region. The remarkable range of Al2O3 v. CaO exhibited by the clinopyroxenes compared with data from other ‘xenolith provinces' emphasizes the extremely complex tectonomagmatic history of the Scottish lithosphere. The generalized age increase from southern and central Scotland to the Northern Highland and Hebridean terranes of the north and NW, with concomitant complexity of geological history, is reflected also by trace element and isotopic studies. Reaction relationships in lherzolites from the Hebridean Terrane, owing to pervasive metasomatism, involve secondary growth of sodic feldspar. This, and light REE enrichment of clinopyroxenes, points to involvement of a natro-carbonatitic melt. Most pyroxenitic xenoliths are inferred to form a basal crustal layer with a generally sharp discontinuity above the underlying (dominantly lherzolitic) mantle. A second discontinuity is inferred to separate these ultramafic cumulates from overlying, broadly cognate metagabbroic cumulates.

Item Type: Article
School or Research Centre: Birkbeck Schools and Research Centres > School of Science > Earth and Planetary Sciences
Depositing User: Administrator
Date Deposited: 15 Aug 2011 13:44
Last Modified: 17 Apr 2013 12:33
URI: http://eprints.bbk.ac.uk/id/eprint/4093

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