LA-ICP-MS study of IAB and IIIAB irons and pallasites: Sub-solidus HSE behavior

E Mullane, O Alard, M Gounelle, Sarah S Russell

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1 Citation (Scopus)

Abstract

We report the concentration of the platinum group elements (PGE) in addition to the highly siderophile elements (HSE) Re and
Au, obtained using LA-ICP-MS, in spatially resolved FeNi-metal (kamacite and taenite) from a suite of IIIAB irons and Brenham
main group pallasite (MGP). These samples are products of fractional crystallization and define a coherent magmatic trend, from
the least evolved (Henbury and Wabar) to the most evolved (Mount Edith). Fractional crystallization continued after segregation of
the pallasite parent melt, and incorporation of olivine into this metal melt did not affect the highly siderophile element systematics.
Solid metal –liquid metal partition coefficients indicate the following compatibility: (1) highly compatible (Re, Os and Ir), (2)
moderately compatible (Pt, Ru and Rh), and (3) incompatible (Pd and Au). This compatibility sequence is broadly consistent with
the melting point systematics of the HSE. The highly fractionated HSE pattern of the evolved IIIAB and Brenham pallasite
indicates that nonmetallic elements such as S play a fundamental role in the evolution of planetisimal core. Taenite – kamacite
partition coefficients (DT/K) illustrate that all of the HSE enter preferentially taenite during subsolidus partitioning and that
subsolidus partitioning is comparable between magmatic and nonmagmatic irons. DT/K appears to be independent of the physical
conditions prevailing on the parent bodies and the light element molar fraction in the bulk composition, but instead the controlling
factors on DT/K behaviour seems to be a combination of the degree of atomic symmetry coupled with atomic radius.
D 2004 Elsevier B.V. All rights reserved.
Original languageEnglish
Pages (from-to)5-28
Number of pages24
JournalMeteoritics and Planetary Science
Volume39
Issue number8
Publication statusPublished - Aug 2004
Event67th Annual Meeting of the Meteoritical-Society - Rio de Janeiro, Brazil
Duration: 2 Aug 20046 Aug 2004

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