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The Albian-Turonian Island Arc Rocks of Tobago, West Indies: Geochemistry, petrogenesis, and Caribbean plate tectonics

Neill, Iain, Kerr, Andrew Craig, Hastie, A. R., Pindell, Jim and Millar, I. L. 2013. The Albian-Turonian Island Arc Rocks of Tobago, West Indies: Geochemistry, petrogenesis, and Caribbean plate tectonics. Journal of Petrology 54 (8) , pp. 1607-1639. 10.1093/petrology/egt025

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Abstract

An elemental and radiogenic isotope study of Cretaceous island arc rocks on Tobago, West Indies, reveals the magmatic processes taking place at the eastern edge of the Pacific-derived Caribbean Plate during development of the Greater Antilles Arc. The ∼110–103 Ma Volcano-Plutonic Suite comprises the ultramafic–intermediate Tobago Pluton and genetically related Tobago Volcanic Group. The volcanic rocks (breccias, tuffs, and mafic–intermediate lavas) have undergone shallow-level fractional crystallization involving plagioclase, clinopyroxene, olivine, and Fe–Ti oxides, but also preserve trace element evidence for ‘cryptic’ amphibole fractionation. The suite is inferred to have formed from a spinel lherzolite mantle wedge source fluxed largely by slab- and recycled volcanogenic sediment-derived fluids. A tonalitic mega-dyke intruding the pluton resembles high-silica adakites, and geochemical constraints indicate a likely origin by partial melting of the arc crust. A mafic dyke swarm (∼103–91 Ma) is partly coeval with the volcanic rocks, but some, perhaps the youngest dykes, are derived from isotopically distinct arc mantle sources compared with the volcanic rocks. Rare Nb-enriched and high-Nb dykes may relate to melting of a high field strength element-enriched source. Current Caribbean tectonic models involve the continuation of east-dipping Farallon Plate subduction beneath the proto-Caribbean seaway either until an Early Cretaceous initiation of proto-Caribbean subduction, or collision of the Caribbean Oceanic Plateau with the Greater Antilles Arc at ∼90–80 Ma. Both models may be compatible with the tectono-magmatic history of Tobago, wherein Tobago is thought to have detached from the fore-arc of the Caribbean arc system during Eocene intra-arc extension, the growth of the Grenada Basin, and inception of the Lesser Antilles Arc. Tobago- or La Désirade-like Mesozoic arc crust underlies much of the present-day Lesser Antilles Arc and not, as has recently been proposed, portions of the plume-derived Caribbean Oceanic Plateau.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: G Geography. Anthropology. Recreation > GC Oceanography
Q Science > QE Geology
Uncontrolled Keywords: Caribbean; island arc; petrogenesis; trace elements; tectonics
Publisher: Oxford Journals
ISSN: 0022-3530
Last Modified: 04 Jun 2017 06:06
URI: http://orca.cf.ac.uk/id/eprint/56496

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