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Titolo:
Tracing a mantle plume: Isotopic and trace element variations of Galapagosseamounts
Autore:
Harpp, KS; White, WM;
Indirizzi:
Colgate Univ, Dept Geol, Hamilton, NY 13346 USA Colgate Univ Hamilton NY USA 13346 niv, Dept Geol, Hamilton, NY 13346 USA Cornell Univ, Dept Geol Sci, Ithaca, NY 14853 USA Cornell Univ Ithaca NY USA 14853 niv, Dept Geol Sci, Ithaca, NY 14853 USA
Titolo Testata:
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
, volume: 2, anno: 2001,
pagine: NIL_1 - NIL_46
SICI:
1525-2027(20010627)2:<NIL_1:TAMPIA>2.0.ZU;2-Q
Fonte:
ISI
Lingua:
ENG
Soggetto:
EAST PACIFIC RISE; SPREADING CENTER SYSTEM; LAMONT SEAMOUNT; OCEANIC BASALTS; NORTH-ATLANTIC; LOIHI SEAMOUNT; PLATE MOTION; HOTSPOT; HELIUM; RIDGE;
Keywords:
Galapagos; hotspot; plume-ridge interaction; isotopes; rare Earth elements; mantle reservoir;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
96
Recensione:
Indirizzi per estratti:
Indirizzo: Harpp, KS Colgate Univ, Dept Geol, Hamilton, NY 13346 USA Colgate Univ Hamilton NY USA 13346 Geol, Hamilton, NY 13346 USA
Citazione:
K.S. Harpp e W.M. White, "Tracing a mantle plume: Isotopic and trace element variations of Galapagosseamounts", GEOCH GEO G, 2, 2001, pp. NIL_1-NIL_46

Abstract

Isotopic and trace element analyses of basalts dredged from across the Galapagos Platform confirm the previously established east facing horseshoe pattern of depleted geochemical signatures at the center of the archipelago and more enriched signatures along the periphery. Statistical analysis of the isotopic data indicates that geochemical variations in the Galapagos cannot be explained by mixing between only the plume and the depleted asthenosphere. Instead, four isotopically distinct end-members must be interacting to account for the subtleties of the Sr, Nd, Pb, and He isotopic data. Threeof the components are geographically restricted: one in the south, one in the central region, and one in the north. These three plume components thenmix with the fourth component, depleted mantle, which is indistinguishablefrom the MORB source. The central component resembles the high He-3/He-4 mantle reservoir that may be common to many plumes and has variously been called PHEM, FOZO, and C by others. Whereas this mantle reservoir appears to make a minor contribution to the composition of most hot spot systems, it may constitute the main body of the Galapagos plume. Geographic distributionof the end-members suggests that the plume is centered near Fernandina similar to 92 degreesN but may be significantly diluted by depleted mantle even near the main conduit. The geochemically distinct end-members trace an eastward mantle flow, manifested as decreasing contributions of the plume in the direction of plate motion. The plume may be tilted by shear in the asthenosphere from plate motion and ambient mantle flow. As it is bent, the plume thermally entrains surrounding upper mantle, resulting in the horseshoe-shaped distribution of depleted and enriched material. The end-members may also outline a deep, strong lateral flow of mantle toward the Galapagos Spreading Center, supplying plume material to the ridge system. Overall, our results suggest that the Galapagos hot spot is both compositionally and dynamically complex owing to its tectonic setting adjacent to a mid-ocean ridge.

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Documento generato il 18/02/20 alle ore 04:11:17