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Hf-Nd isotope constraints on the origin of the Cretaceous Caribbean plateau and its relationship to the Galapagos plume

Thompson, P. M. E., Kempton, P. D., White, R. V., Kerr, Andrew Craig, Tarney, J., Saunders, A. D., Fitton, J. G. and McBirney, A. 2004. Hf-Nd isotope constraints on the origin of the Cretaceous Caribbean plateau and its relationship to the Galapagos plume. Earth and Planetary Science Letters 217 (1-2) , pp. 59-75. 10.1016/S0012-821X(03)00542-9

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Abstract

Formation of the Cretaceous Caribbean plateau, including the komatiites of Gorgona, has been linked to the currently active Gala¤pagos hotspot. We use Hf^Nd isotopes and trace element data to characterise both the Caribbean plateau and the Gala¤pagos hotspot, and to investigate the relationship between them. Four geochemical components are identified in the Gala¤pagos mantle plume: two ‘enriched’ components with OHf and ONd similar to enriched components observed in other mantle plumes, one moderately enriched component with high Nb/Y, and a fourth component which most likely represents depleted MORB source mantle. The Caribbean plateau basalt data form a linear array in Hf^Nd isotope space, consistent with mixing between two mantle components. Combined Hf^ Nd^Pb^Sr^He isotope and trace element data from this study and the literature suggest that the more enriched Caribbean end member corresponds to one or both of the enriched components identified on Gala¤pagos. Likewise, the depleted end member of the array is geochemically indistinguishable from MORB and corresponds to the depleted component of the Gala¤pagos system. Enriched basalts from Gorgona partially overlap with the Caribbean plateau array in OHf vs. ONd, whereas depleted basalts, picrites and komatiites from Gorgona have a high OHf for a given ONd, defining a high-OHf depleted end member that is not observed elsewhere within the Caribbean plateau sequences. This component is similar, however, in terms of Hf^Nd^Pb^He isotopes and trace elements to the depleted plume component recognised in basalts from Iceland and along the Reykjanes Ridge. We suggest that the Caribbean plateau represents the initial outpourings of the ancestral Gala¤pagos plume. Absence of a moderately enriched, high Nb/Y component in the older Caribbean plateau (but found today on the island of Floreana) is either due to changing source compositions of the plume over its 90 Ma history, or is an artifact of limited sampling. The high-OHf depletedcomponent sampled by the Gorgona komatiites and depleted basalts is unique to Gorgona and is not found in the Caribbean plateau. This may be an indication of the scale of heterogeneity of the Caribbean plateau system; alternatively Gorgona may represent a separate oceanic plateau derived from a completely different Pacific plume, such as the Sala y Gomez.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QE Geology
Uncontrolled Keywords: Caribbean plateau ; Gala¤pagos plume ; Gorgona ; Hafnium ; neodymium ; Cretaceous.
ISSN: 0012-821X
Last Modified: 04 Jun 2017 02:04
URI: http://orca.cf.ac.uk/id/eprint/8460

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