Emplacement styles within the Land's End Granite, West Cornwall

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Emplacement styles within the Land's End Granite, West Cornwall

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dc.contributor.author Powell, T. en_US
dc.contributor.author Salmon, S. en_US
dc.contributor.author Clark, A.H. en_US
dc.contributor.author Shail, R.K. en_US
dc.date.accessioned 2012-07-18T13:54:39Z en_US
dc.date.accessioned 2013-03-20T12:59:21Z
dc.date.issued 1999 en_US
dc.description.abstract The Land's End Granite is the youngest of the major plutons of the Cornubian batholith and comprises a number of discrete bodies of both coarse-grained granite (CGG) and fine-grained granite (FGG). Detailed re-mapping of selected parts of the composite Land's End pluton indicates that individual granite intrusions take a variety of forms, including dykes and sub-horizontal sheets. U-Pb (monazite) and 40Ar-39Ar (muscovite) age data have been interpreted elsewhere to indicate that the CGG and FGG of the northern "Zennor lobe" were emplaced c. 2-3 m.y. before the CGG and FGG of the southern "St Buryan lobe". Separating the two lobes is a large body of aphyric granite, the "St Just wedge", which is as yet undated. Relationships at Porth Nanven, where an irregular contact is discordant to a magmatic-state fabric in CGG of the St Buryan lobe, and at Porth Ledden, where sheets of aphyric granite intrude CGG, suggest that the St Just wedge is younger than the two main lobes. The composite nature of the pluton is exemplified by variations in grainsize and texture and in the size, abundance and alignment of alkali-feldspar phenocrysts. The subtle nature of petrographic variation in such felsic rocks makes identification of contacts between CGGs difficult, but those between CGG and FGG are more easily recognizable. At Bosigran, there is a laterally persistent northwest dipping sheet of CGG which exhibits a sharp, planar contact with underlying MGG. Immediately to the north, at Carn Veslan, the same MGG has a gradational contact with non-porphyritic FGG. At Sennen and Land's End, contacts between slightly different CGGs are denoted by the presence of distinct mafic zones, planar at Sennen and much more irregular at Land's End. The contrasting nature of these contacts suggests different time-intervals between intrusive events. At Porth Nanven, granite dykes with sharp, planar margins intrude the aphyric granite of the St Just wedge. Throughout the pluton, bodies of FGG demonstrate a variety of temporal relationships with adjoining CGG, including contemporaneous, sub-rounded masses and later sub-horizontal sheets. These and other examples within the Land's End Granite demonstrate that, rather than having originated as a large, diapirically emplaced magma body, as suggested in earlier models, the pluton is composed of a series of discrete intrusions. en_GB
dc.identifier.citation Vol. 9 (4), pp. 333 - 339 en_GB
dc.identifier.uri http://hdl.handle.net/10036/3658 en_US
dc.language.iso en en_GB
dc.publisher The Ussher Society en_GB
dc.relation.url http://www.ussher.org.uk/ en_GB
dc.title Emplacement styles within the Land's End Granite, West Cornwall en_GB
dc.type Article en_GB
dc.date.available 2012-07-18T13:54:39Z en_US
dc.date.available 2013-03-20T12:59:21Z
dc.identifier.issn 0566-3954 en_US
exeter.contacts.depositing-owner-email Shail, Robin <R.K.Shail@exeter.ac.uk> en_US
exeter.contacts.owner-email Shail, Robin <R.K.Shail@exeter.ac.uk> en_US
dc.identifier.journal Geoscience in South-West England en_GB
pubs.organisational-data /Symplectic Joint Venture en_US
pubs.organisational-data /Symplectic Joint Venture/Exeter en_US
pubs.organisational-data /Symplectic Joint Venture/Exeter/All Exeter Users en_US
pubs.organisational-data /Symplectic Joint Venture/Exeter/College of Engineering, Mathematics & Physical Sciences en_US
pubs.organisational-data /Symplectic Joint Venture/Exeter/College of Engineering, Mathematics & Physical Sciences/All Academic Staff (CEMPS) en_US
pubs.organisational-data /Symplectic Joint Venture/Exeter/College of Engineering, Mathematics & Physical Sciences/Camborne School of Mines en_US


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