Constraints on Earth accretion deduced from noble metals in the oceanic mantle

Jonathan E. Snow () and Gerhard Schmidt
Additional contact information
Jonathan E. Snow: Max-Planck-Institut für Chemie (Otto-Hahn-Institut)
Gerhard Schmidt: Institut für Kernchemie, Johannes Gutenberg-Universität Mainz

Nature, 1998, vol. 391, issue 6663, 166-169

Abstract: Abstract If the Earth's mantle were in equilibrium with its core, the mantle would contain three orders of magnitude less of the noble metals (platinum-group elements Pt, Os, Ir, Ru, Pd and Rh, plus Au and Re) than are observed. An explanation put forward to account for this disparity has been that the last 1% of the Earth's accretion occurred after the iron-rich core had separated from the mantle1,2. Recent debate has accordingly centred on which meteorite class or classes made up this ‘late veneer’ of accretion3. Here we present analyses of noble-metal concentrations in oceanic peridotites (plutonic rocks which are thought to represent samples of the Earth's upper mantle). We find that the average oceanic-mantle Os/Ir ratio is indistinguishable from that in the CI-type carbonaceous chondrites4, but that Ru/Ir, Pt/Ir, Rh/Ir and Pd/Ir ratios are about 40% higher. A late veneer composed of strictly CI-type carbonaceous chondritic composition is therefore not compatible with these observations. The data also allows us to rule out other carbonaceous chondrites5, enstatite chondrites6,7 and ordinary chondrites8 as significant late veneer components. We propose that mixing of differentiated outer-core material back into the mantle after core separation could account for the observed noble-metal ratios and abundances in the mantle without any late accretionary veneer.

Date: 1998
References: Add references at CitEc
Citations:

Downloads: (external link)
https://www.nature.com/articles/34396 Abstract (text/html)
Access to the full text of the articles in this series is restricted.

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:nat:nature:v:391:y:1998:i:6663:d:10.1038_34396

Ordering information: This journal article can be ordered from
https://www.nature.com/

DOI: 10.1038/34396

Access Statistics for this article

Nature is currently edited by Magdalena Skipper

More articles in Nature from Nature
Bibliographic data for series maintained by Sonal Shukla () and Springer Nature Abstracting and Indexing ().