The Foyers Granitic Complex and its aureole

The field mapping of the Foyers Granitic Complex and its psammite envelope provided data to study the emplacement of the complex, and produce part of British Geological Survey Sheet 73E. The complex contains quartz diorite cut by quartz monzodiorite in the north, granodiorite in the south, and cross cutting adamellite stocks throughout the pluton. These units are the products of a differentiating magma body at depth. A north easterly trending suite of microdiorite dykes cross cuts the complex. The complex was emplaced into Grampian Group psammites, after the cessation of Caledonian orogenesis, and developed an extensive thermal aureole, with minor anatexis occuring in the inner aureole. Granitoid fabrics, enclaves, xenoliths and internal contacts imply emplacement whilst in a magmatic state. The adamellite was emplaced into a solid pluton. Boudinage and shearing in envelope psammites, and intense solid state fabrics in pre-Foyers granitoids, indicate the envelope shortened perpendicular to the complex margin. Major and minor D1, D2 and D3 regional structures are not rotated by granitoid emplacement. The orientations of the contact parallel psammite units are controlled by regional structures. Contact relationships between envelope and complex imply sloping was the major intrusion mechanism, with siliceous lithologies more readily sloped than others. Low density contrasts between granitoid and envelope necessitate sloping occured whilst the pluton was very fluid, extra bouyancy perhaps derived from connection with a magma source at depth. The Foyers Complex was emplaced as a series of stocks sloping into the crust. Regional structures controlled the morphology of the magma chamber because certain stratigraphic units either facilitated or hindered sloping. The positions of these units are controlled by regional structure. Ballooning of the magma chamber occured whilst the entire complex was fluid and deformed the envelope.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

City of London Polytechnic

Year dc:date.issued

1990

Author dc:creator

• Hood, Philip Thomas.

• 550 - Earth Sciences

Dc Identifier Grantnumber

N/A

OAI identifier oai:identifier

oai:repository.londonmet.ac.uk:3040