High U/Th partitioning by clinopyroxene from alkali silicate and carbonatite metasomatism

An origin for Th/U disequilibrium in mantle melts?

S. F. Foley*, C. M. Petibon, G. A. Jenner, B. A. Kjarsgaard

*Corresponding author for this work

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Clinopyroxene/melt pairs in strongly potassic silicate and carbonatite melts exhibit unusually high U/Th partitioning ratios of ~ 3 and ~ 2, respectively. These values are much higher than those found for aluminous clinopyroxenes in peridotite, and have the potential to cause significant (230Th)/ (238U) isotope enrichment in volcanics. The potassic silicate (lamproite) and carbonatite melts correspond closely to the main agents of mantle metasomatism, indicating that clinopyroxene in metasomatized regions of the mantle may greatly affect U/Th disequilibria. Recycling of alkali pyroxenite veins in the oceanic lithosphere formed by solidification of melt in the extremities of the MORB melting region presents an alternative to eclogite recycling in MORB and OIB genesis.

Original languageEnglish
Pages (from-to)104-109
Number of pages6
JournalTerra Nova
Volume13
Issue number2
DOIs
Publication statusPublished - 1 Apr 2001
Externally publishedYes

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