Partitioning of lithophile trace elements between H 2O and H 2O + CO 2 fluids and topaz rhyolite melt

J. D. Webster, J. R. Holloway, Richard Hervig

Research output: Contribution to journalArticle

173 Scopus citations

Abstract

Experiments have been conducted with H 2O and H 2O+CO 2-bearing fluids and melts of a Cl-, F-, and lithophile trace element-enriched vitrophyre associated with topaz rhyolite from Spor Mountain, Utah. The partitioning of Li, Rb, Sr, Y, Nb, Cs, and Ce between aqueous fluids and melts of topaz rhyolite composition depends strongly on temperature and pressure. In the presence of CO 2-free aqueous fluids at 4 kbars and at temperatures of 770° to 950°C, all lithophile elements partition in favor of the melt. This behavior for lithophile elements mimics that of published data on the partitioning of Pb and Zn between rhyolitic melts and Cl-bearing fluids. Fluid/melt distribution coefficients for the lithophile trace elements are significantly smaller for topaz rhyolite melts in equilibrium with mixed CO 2+H 2O fluids than for topaz rhyolite melts plus CO 2-free aqueous fluids. For equilibrium between topaz rhyolite melt and aqueous fluids at 2 kbars and 800°C, the distribution coefficients of Li, Rb, Sr, Y, Nb, Cs, Ba, and Ce increase as the Cl concentration of the fluid increases from 0.2 m to >6 m. Water-saturated magmas of topaz rhyolite composition may become differentiated with respect to Li, Cs, and Rb (±Ce, Y, and Nb) if an aqueous fluid phase is evolved and moves through the magma under the influence of a temperature gradient that has a maximum temperature of at least 850° to 900°C.

Original languageEnglish (US)
Pages (from-to)116-134
Number of pages19
JournalEconomic Geology
Volume84
Issue number1
DOIs
StatePublished - Jan 1 1989

ASJC Scopus subject areas

  • Geophysics
  • Geology
  • Geochemistry and Petrology
  • Economic Geology

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