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Titolo:
Ir, Ru, Pt, and Pd in basalts and komatiites: New constraints for the geochemical behavior of the platinum-group elements in the mantle
Autore:
Rehkamper, M; Halliday, AN; Fitton, JG; Lee, DC; Wieneke, M; Arndt, NT;
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, Zentrallabor 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 Univ Kiel, Inst Geol, D-24118 Kiel, Germany Univ Kiel Kiel Germany D-24118 iv Kiel, Inst Geol, D-24118 Kiel, Germany Univ Rennes 1, Inst Geol, F-35042 Rennes, France Univ Rennes 1 Rennes France F-35042 1, Inst Geol, F-35042 Rennes, France
Titolo Testata:
GEOCHIMICA ET COSMOCHIMICA ACTA
fascicolo: 22, volume: 63, anno: 1999,
pagine: 3915 - 3934
SICI:
0016-7037(199911)63:22<3915:IRPAPI>2.0.ZU;2-L
Fonte:
ISI
Lingua:
ENG
Soggetto:
MIDOCEAN RIDGE BASALTS; SILICATE MELT; TRACE-ELEMENT; PRIMARY MAGMAS; CAMEROON LINE; RE-OS; GEOLOGICAL SAMPLES; SULFUR SATURATION; OCEANIC-CRUST; NOBLE-METALS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
85
Recensione:
Indirizzi per estratti:
Indirizzo: Rehkamper, M Univ Michigan, Dept Geol Sci, Ann Arbor, MI 48109 USA Univ Michigan Ann Arbor MI USA 48109 Ann Arbor, MI 48109 USA
Citazione:
M. Rehkamper et al., "Ir, Ru, Pt, and Pd in basalts and komatiites: New constraints for the geochemical behavior of the platinum-group elements in the mantle", GEOCH COS A, 63(22), 1999, pp. 3915-3934

Abstract

The concentrations of the platinum-group elements (PGE) Ir, Ru, Pt, and Pdwere determined in 18 mantle-derived basalts from a variety of tectonic settings and six komatiites from three locations. All analyses were performedusing isotope dilution, Carius tube digestion, and the precise technique of multiple collector inductively coupled plasma mass spectrometry. Multipleanalyses of two samples indicate external reproducibilities, based upon separate dissolutions, of approximately 2-9% in the, ppt to ppb concentrationrange. Mid-ocean ridge basalts from the Kolbeinsey Ridge, tholeiites from Icelandand alkali basalts from the Cameroon Line define three individual sample suites that are characterized by distinct major, trace, and platinum-group element systematics. All three-sample suites display correlations of the PGEwith MgO, Ni, and Cr. The new analytical results are employed to constrainthe geochemical behavior of the PGE during the formation and differentiation of mantle-derived melts. The PGE are inferred to be compatible in sulfides during partial melting with sulfide-silicate melt partition coefficientsof similar to 1 X 10(4). The fractionated PGE patterns of mantle melts area consequence of the incompatibility of Pd in nonsulfide phases, whereas Ir and Ru must be compatible in at least one other mantle phase. Model calculations indicate that PGE alloys or spinel may be responsible for the higher compatibility of the latter elements during partial melting. It is further demonstrated that the shape of the melting regime has a profound effect on the PGE systematics of mantle magmas. The systematic trends of the three sample suites in plots of PGE against Ni and Cr are the result of magma differentiation processes that involve fractional crystallization of silicate minerals and the concurrent segregationof an immiscible sulfide liquid. The behavior of the PGE during magma fractionation indicates that the segregated sulfides probably equilibrate with >90% of the silicate magma and that PGE scavenging by sulfides is best described by a combination of batch and fractional equilibrium partitioning. Copyright (C) 1999 Elsevier Science Ltd.

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Documento generato il 27/11/20 alle ore 10:40:06