Heterogeneous Accretion and the Moderately Volatile Element Budget of Earth

• Published in: Science (American Association for the Advancement of Science) Vol. 328; no. 5980; pp. 884 - 887
• Main Authors: Schönbächler, M, Carlson, R.W, Horan, M.F, Mock, T.D, Hauri, E.H
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 14-05-2010; The American Association for the Advancement of Science
• Subjects: Accretion; Carbonaceous chondrites; Chemical elements; Chondrites; Chromium; Cosmochemistry. Extraterrestrial geology; Earth; Earth mantle; Earth sciences; Earth, ocean, space; Evolution; Exact sciences and technology; Extraterrestrial geology; Geochemistry; Internal geophysics; Isotope geochemistry; Isotope geochemistry. Geochronology; Isotopes; Mantle; Market disequilibrium; Materials; Mathematical models; Moisture content; Planetary composition; Planetology; Precursors; Protoplanets; Solar systems; Solid-earth geophysics, tectonophysics, gravimetry; meteorites; chromium; Moon; mixing; strontium; oxidation; chondrites; evolution; impacts; heterogeneity; stony meteorites; Earth; accretion; enrichment; core; isotopes; water content; mantle; palladium; silver; growth; volatile elements
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1186239

Several models exist to describe the growth and evolution of Earth; however, variables such as the type of precursor materials, extent of mixing, and material loss during accretion are poorly constrained. High-precision palladium-silver isotope data show that Earth's mantle is similar in ¹⁰⁷Ag/¹⁰⁹Ag to primitive, volatile-rich chondrites, suggesting that Earth accreted a considerable amount of material with high contents of moderately volatile elements. Contradictory evidence from terrestrial chromium and strontium isotope data are reconciled by heterogeneous accretion, which includes a transition from dominantly volatile-depleted to volatile-rich materials with possibly high water contents. The Moon-forming giant impact probably involved the collision with a Mars-like protoplanet that had an oxidized mantle, enriched in moderately volatile elements.