U-Th isotopes in arc magmas

Implications for element transfer from the subducted crust

C. J. Hawkesworth*, S. P. Turner, F. McDermott, D. W. Peate, P. Van Calsteren

*Corresponding author for this work

Research output: Contribution to journalArticle

625 Citations (Scopus)

Abstract

Uranium-thorium isotope results from island arc volcanic rocks were used to investigate the rates of transfer of fluids and sediments from the downgoing slab. Uranium, but not thorium, is readily mobilized in the fluid. A negative array between thorium/cerium and neodymium-143/neodymium-144 indicates that significant amounts of the thorium in arc rocks are derived from subducted sediments, although perhaps only about 30 percent of the thorium in subducted sediments is returned to the crust in this way. The transfer times for fluid through the mantle wedge are about 30,000 to 120,000 years, whereas those for sediment melts may be several million years. The low average uranium/thorium ratios of bulk crust primarily reflect different crustal generation processes in the Archaean.

Original languageEnglish
Pages (from-to)551-555
Number of pages5
JournalScience
Volume276
Issue number5312
DOIs
Publication statusPublished - 25 Apr 1997
Externally publishedYes

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