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Hafnium isotopic variations in volcanic rocks from the Caribbean Large Igneous Province and Galapagos hot spot tracks

Geldmacher, J., Hanan, B. B., Blichert-Toft, J., Harpp, K., Hoernle, K., Hauff, F., Werner, R. and Kerr, Andrew 2003. Hafnium isotopic variations in volcanic rocks from the Caribbean Large Igneous Province and Galapagos hot spot tracks. Geochemistry, Geophysics, Geosystems 4 (7) , 1062. 10.1029/2002GC000477

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Abstract

We report Hf isotope compositions of 79 lavas that record the early (�5–95 Ma) history of the Gala´pagos plume volcanism. These include lavas from the Caribbean Large Igneous Province (CLIP; �95–70 Ma), the accreted Gala´pagos paleo-hot spot track terranes (54–65 Ma) of Costa Rica (Quepos, Osa and Burica igneous complexes), and the Gala´pagos hot spot tracks (<20 Ma) located on the Pacific seafloor (Cocos, Carnegie, Malpelo, and Coiba Ridges and associated seamounts). These samples have previously been well characterized in terms of major and trace elements, Sr-Nd-Pb isotopes and Ar/Ar ages. As a result of the relative immobility of the high field strength and rare earth elements during synand post-emplacement hydrothermal activity and low-temperature alteration, combined Lu-Hf and Sm-Nd isotope systematics, when used in conjunction with Pb isotopes, provide a particular powerful tool, for evaluating the source compositions of ancient and submarine lavas. The combined Nd-Hf isotope data suggest that three of the isotopically distinct source components found today in the Gala´pagos Islands (the Floreana-like southern component, the Fernandina-like central component, and the depleted Genovesa-like eastern component) were present in the CLIP already by 95–70 Ma. The fourth Pinta-like northern component is first recorded at about 83–85 Ma by volcanism taking place during the transition from the plume head/CLIP to plume tail stage and has then been present in the hot spot track continuously thereafter. The identification of the unique northern and southern Gala´pagos Plume Hf-Nd-Pb isotope source signatures within the CLIP and the oldest hot spot track lavas provides direct evidence that the CLIP represents the plume head stage of the Gala´pagos hot spot. Hafnium isotopes are consistent with the possibility that two types of sediment components may have contributed to the Hf, Nd and Pb isotope compositions of the Gala´pagos plume lavas. One component, characterized by D207Pb/204Pb � 0 and high positive DeHf has an isotope signature indicative of relatively recently recycled pelagic sediment, a signature typical of the southern Gala´pagos island Floreana. The other component has an EM like isotopic composition resembling modern seafloor sediments with positive D207Pb/204Pb and lower DeHf, a signature typical of the northern Gala´pagos island Pinta.

Item Type: Article
Date Type: Publication
Status: Published
Uncontrolled Keywords: Hafnium isotopes ; Caribbean Igneous Province ; Galapagos ; Mantle plumes; Hot spot track.
Additional Information: Pdf uploaded in accordance with publisher's policy at http://www.sherpa.ac.uk/romeo/issn/1525-2027/ (accessed 20/02/2014).
Publisher: American Geophysical Union.
ISSN: 1525-2027
Date of First Compliant Deposit: 30 March 2016
Last Modified: 04 Jun 2017 02:04
URI: http://orca.cf.ac.uk/id/eprint/8459

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