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Titolo:
Non-chondritic platinum-group element ratios in oceanic mantle lithosphere: petrogenetic signature of melt percolation?
Autore:
Rekhamper, M; Halliday, AN; Alt, J; Fitton, JG; Zipfel, J; Takazawa, E;
Indirizzi:
Univ Michigan, Dept Geol Sci, Ann Arbor, MI 48109 USA Univ Michigan Ann Arbor MI USA 48109 pt Geol Sci, Ann Arbor, MI 48109 USA Univ Munster, Zent Labor Geochronol, D-48149 Munster, Germany Univ Munster Munster Germany D-48149 eochronol, D-48149 Munster, Germany ETH Zurich, Dept Earth Sci, Inst Isotope Geol & Mineral Resources, CH-8092Zurich, Switzerland ETH Zurich Zurich Switzerland CH-8092 ources, CH-8092Zurich, Switzerland Univ Edinburgh, Dept Geol & Geophys, Edinburgh EH9 3JW, Midlothian, Scotland Univ Edinburgh Edinburgh Midlothian Scotland EH9 3JW Midlothian, Scotland Max Planck Inst Chem, D-55020 Mainz, Germany Max Planck Inst Chem Mainz Germany D-55020 Chem, D-55020 Mainz, Germany Niigata Univ, Fac Sci, Dept Geol, Niigata 9502102, Japan Niigata Univ Niigata Japan 9502102 ci, Dept Geol, Niigata 9502102, Japan
Titolo Testata:
EARTH AND PLANETARY SCIENCE LETTERS
fascicolo: 1-2, volume: 172, anno: 1999,
pagine: 65 - 81
SICI:
0012-821X(19991015)172:1-2<65:NPERIO>2.0.ZU;2-P
Fonte:
ISI
Lingua:
ENG
Soggetto:
ABYSSAL PERIDOTITES; SIDEROPHILE ELEMENTS; GEOLOGICAL SAMPLES; NOBLE-METALS; SULFIDE; ABUNDANCE; ORIGIN; EARTH; SEGREGATION; MIGRATION;
Keywords:
platinum group; geochemistry; igneous rocks; genesis; models; mantle; percolation;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
50
Recensione:
Indirizzi per estratti:
Indirizzo: Rekhamper, M Univ Michigan, Dept Geol Sci, 1006 CC Little Bldg, Ann Arbor,MI 48109 USA Univ Michigan 1006 CC Little Bldg Ann Arbor MI USA 48109 USA
Citazione:
M. Rekhamper et al., "Non-chondritic platinum-group element ratios in oceanic mantle lithosphere: petrogenetic signature of melt percolation?", EARTH PLAN, 172(1-2), 1999, pp. 65-81

Abstract

The concentrations of the platinum-group elements (PGE) Ir, Ru, Pt and Pd were determined in 11 abyssal peridotites from ODP Sites 895 and 920, as well in six ultramafic rocks from the Horoman peridotite body, Japan, which is generally thought to represent former asthenospheric mantle. Individual oceanic peridotites from ODP drill cores are characterized by variable absolute and relative PGE abundances, but the average PGE concentrations of bothODP suites are very similar. This indicates that the distribution of the noble metals in the mantle is characterized by small-scale heterogeneity andlarge-scale homogeneity. The mean Ru/Ir and Pt/Ir ratios of all ODP peridotites are within 15% and 3%, respectively, of CI-chondritic values. These results are consistent with models that advocate that a late veneer of chondritic material provided the present PGE budget of the silicate Earth. The data are not reconcilable with the addition of a significant amount of differentiated outer core material to the upper mantle. Furthermore, the resultsof petrogenetic model calculations indicate that the addition of sulfides derived from percolating magmas may be responsible for the variable and generally suprachondritic Pd/Ir ratios observed in abyssal peridotites. Ultramafic rocks from the Horoman peridotite have PGE signatures distinct from abyssal peridotites: Pt/Ir and Pd/Ir are correlated with lithophile element concentrations such that the most fertile Iherzolites are characterized by non-primitive PGE ratios. This indicates that processes more complex than simple in-situ melt extraction are required to produce the geochemical systematics, if the Horoman peridotite formed from asthenospheric mantle with chondritic relative PGE abundances. In this case, the PGE results can be explained by melt depletion accompanied or followed by mixing of depleted residues with sulfides, with or without the addition of basaltic melt. (C) 1999 Elsevier Science B.V. All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 28/11/20 alle ore 18:47:55