Distribution of W and Mo in ordinary chondrites and implications for nebular and parent body thermal processes

Ping Kong, Mitsuru Ebihara

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

W and Mo abundances in the bulk metals of 10 H, 5 L and 6 LL chondrites were determined by instrumental neutron activation analysis (INAA). Partitioning of W and Mo between metal and non-metal phases was evaluated by comparing Ni-normalized W and Mo abundances in the metal phases with those in the bulk samples. It is observed that W distributions differ significantly between equilibrated ordinary chondrites (EOCs) and unequilibrated ordinary chondrites (UOCs). However, no correlation is confirmed between the W distribution and the petrographic type for EOCs. This implies that the W partitioning among mineral phases can provide a clue for estimating the metamorphic temperature intervening between EOCs and UOCs. The difference in W equilibrium temperatures was observed among H, L and LL chondrite groups and it may correspond to the difference in cooling rates and subsequently in sizes of the chondrite parent bodies; LL chondrites have the lowest equilibrium temperature and, hence, have the largest parent body, whereas H chondrites have the highest equilibrium temperature and the smallest parent body. Mo/W abundance ratios remain constant in EOC metals, but are variable in UOC metals, suggesting that the W solid equilibrium has not been achieved in UOCs. The W and Mo distributions in UOCs still preserve the characteristics of W and Mo in the nebula, which demonstrates that the chondritic metal was formed by melting highly oxidized precursors before or during the accretion of chondrite parent bodies.

Original languageEnglish
Pages (from-to)83-93
Number of pages11
JournalEarth and Planetary Science Letters
Volume137
Issue number1-4
Publication statusPublished - 1996 Jan
Externally publishedYes

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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