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Geochemical characteristics and geotectonic setting of early Ordovician basalt lavas in the Ballantrae Complex ophiolite, SW Scotland

Smellie, J.L.; Stone, P.. 2001 Geochemical characteristics and geotectonic setting of early Ordovician basalt lavas in the Ballantrae Complex ophiolite, SW Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences, 91 (3-4). 539-555. 10.1017/S0263593300008385

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Abstract/Summary

The consensus of several geochemical studies is a polygenetic origin for the basic volcanic sequence within the Ballantrae Complex ophiolite. This overall agreement masks differences of opinion regarding local geochemical interpretation, the possible correlation of structurally isolated lava tracts, and the degree of structural imbrication responsible for the juxtaposition of the various lava types. Newly acquired data (XRF, INAA, ICP-MS) provide the best evidence yet obtained for the presence of a MORB component and establish a wider distribution for primitive tholeiitic basalts with plate-margin characteristics than had been previously reported. The two principal within-plate sequences (well established from extensive coastal outcrop) are geochemically indistinguishable, with one considered to be the deeper water equivalent of the other. Lithofacies and geochemical similarities encourage correlation of some inland and sparsely exposed examples of within-plate basalt with the well-exposed coastal sequences, and all of this lava type may have originated from a single, ocean island volcano. The diversity of outcrops formed in within-plate and plate-margin geotectonic settings is combined within a dynamic reconstruction of a Tremadoc to Arenig arc-trench system with an active back-arc spreading region. The new reconstruction reconciles for the first time all of the known geochemical and published isotopic age evidence.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1017/S0263593300008385
Programmes: BGS Programmes > Geology and Landscape Northern
BAS Programmes > Pre 2000 programme
ISSN: 0263-5933
Additional Keywords: back-arc spreading, boninite, island arc, marginal basin, island arc, MORB, ocean island
Date made live: 09 Nov 2012 11:02
URI: http://nora.nerc.ac.uk/id/eprint/20290

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