Geochemistry and tectonomagmatic significance of Lower Cretaceous island arc lavas from the Devils Racecourse Formation, eastern Jamaica
Published:January 01, 2009
Alan R. Hastie, Andrew C. Kerr, Simon F. Mitchell, Ian L. Millar, 2009. "Geochemistry and tectonomagmatic significance of Lower Cretaceous island arc lavas from the Devils Racecourse Formation, eastern Jamaica", The Origin and Evolution of the Caribbean Plate, K. H. James, M. A. Lorente, J. L. Pindell
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The Benbow Inlier in Jamaica contains the Devils Racecourse Formation, which is composed of a Hauterivian to Aptian island arc succession. The lavas can be split into a lower succession of basaltic andesites and dacites/rhyolites, which have an island arc tholeiite (IAT) composition and an upper basaltic and basaltic andesite sequence with a calc-alkaline (CA) chemistry. Trace element and Nd–Hf isotopic evidence reveals that the IAT and CA lavas are derived from two chemically similar mantle wedge source regions predominantly composed of normal mid-ocean ridge-type spinel lherzolite. In addition, Th-light rare earth element/high field strength element–heavy rare earth element ratios, Nd–Hf isotope systematics, (Ce/Ce*)n-mn and Th/La ratios indicate that the IAT and CA mantle wedge source regions were enriched by chemically distinct slab fluxes, which were derived from both the altered basaltic portion of the slab and its accompanying pelagic and terrigenous sedimentary veneer respectively. The presence of IAT and CA island arc lavas before and after the Aptian–Albian demonstrates that the compositional change in the Great Arc of the Caribbean was the result of the subduction of chemically differing sedimentary material. There is therefore no evidence from the geochemistry of this lava succession to support arc-wide subduction polarity reversal in the Aptian–Albian.
Supplementary material: References for data sources used in figures can be found at: http://www.geolsoc.org.uk/SUP18361.
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The Origin and Evolution of the Caribbean Plate
This book considers the geology between North and South America. It contributes to debate about the area's evolution, particularly that of the Caribbean. Prevailing understanding is that the Caribbean formed in the Pacific and was engulfed between the Americas as the latter drifted west. Accordingly, the Caribbean Plate comprises internal, Jurassic–Cretaceous oceanic rocks, thickened into a Cretaceous hotspot/plume plateau, with obducted ophiolites and Cretaceous–Palaeogene, subduction-related, intra-oceanic volcanic arc and metamorphosed arc/continental rocks exposed on its margins. An alternative interpretation is that the Caribbean evolved in place. It consists largely of continental crust, extended in the Triassic–Jurassic, which subsided below thick Jurassic–Cretaceous carbonate rocks and flood basalts, and Cenozoic carbonate and clastic rocks. After uplift of ‘oceanic’ and volcanic arc rocks onto (continental) margins, the interior foundered in the Middle Eocene. Papers range from regional overviews and discussions of Caribbean origins to aspects of local geology arranged in a circum-Caribbean tour and ending in the interior. They address tectonics, structure, geochronology, seismicity, igneous and metamorphic petrology, metamorphism, geochemistry, stratigraphy and palaeontology.