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          Institute: MPI für Chemie     Collection: Publikationen MPI für Chemie     Display Documents

ID: 14546.0, MPI für Chemie / Publikationen MPI für Chemie
Os isotopes in mantle xenoliths from the Eifel volcanic field and the Vogelsberg (Germany): age constraints on the lithospheric mantle
Authors:Schmidt, G.; Snow, J.
Date of Publication (YYYY-MM-DD):2002-09
Title of Journal:Contributions to Mineralogy and Petrology
Journal Abbrev.:Contrib. Mineral. Petrol.
Issue / Number:6
Start Page:694
End Page:705
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:The effects of mantle metasomatism on the sulfide phase in mantle xenoliths in general, and on the Os isotopic system in particular, have received increased attention in recent years. Here, we report on Os isotopic systematics of metasomatized mantle xenoliths from the late Quaternary Eifel (Dreiser Weiher and Meerfelder Maar) and neighboring Vogelsberg volcanic fields, which provide insight into the effects of melt extraction and metasomatism on Os isotopes and place constraints on the evolution of the lithospheric mantle component beneath central Europe. Sixteen harzburgite, lherzolite, and pyroxenite xenoliths from the Eifel and two lherzolite xenoliths from the Vogelsberg were analyzed for Os isotopes. Samples from the anhydrous peridotite suite (Ib) are highly variable in their Os isotopes, ranging from subchondritic values (Os-187/Os-188=0.1236) to suprachondritic values (Os-187/Os-188=0.1420), indicating that some of these samples have been overprinted by the addition of radiogenic Os and have lost the primary mantle Os that was presumably present. The suprachondritic values suggest a source for this Os in a reservoir with a time-integrated Re/Os ratio greater than that of the bulk Earth. Eifel samples with Os contents > 1.5 ng/g from the hydrous suite (la) have relatively unradiogenic Os isotope compositions (Os-187/Os-188=0.1208- 0.1237) and Al2O3-Os isotopic systematics consistent with ancient melt depletion and isolation from the convecting asthenospheric mantle for time periods similar to the age of the overlying crust (similar to1.5 Ga) as well with results from peridotite massifs in the European region. The LREE- metasomatism and the enrichment of Os (up to 6.47 ng/g) and As (sulfide metasomatism?) in the hydrous suite is strongly inversely correlated with the Os isotope ratios, demonstrating that mantle processes such as metasomatism can significantly modify the Os isotope chemistry of mantle xenoliths.
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Chemie/Geochemie
External Affiliations:Univ Cologne, Inst Mineral & Geochem, D-5000 Cologne 41, Germany; Univ Mainz, Inst Kernchem, D-6500 Mainz, Germany
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