Hornblende-melt trace-element partitioning measured by ion microprobe

Chemical Geology



Trace-element abundances were measured in situ by ion microprobe in five samples of hornblende and melt ranging from basaltic andesite to high-silica rhyolite. Except for one sample, for which quench overgrowth or disequilibrium is suspected, the abundance ratios show systematic inter-element and inter-sample variations, and probably approach true partition coefficients. Apparent partition coefficients are reported for La, Ce, Nd, Sm, Dy, Er, Yb, Sc, Ti, V, Cr, Sr, Y and Zr. Rare-earth elements (REE) and Y form smooth convex-upward partitioning patterns that rise to higher D-values and become increasingly convex in more evolved samples. Apparent partition coefficients for REE, Y, Ti, V and Cr can be parameterized as functions of the distribution of Ca between hornblende and melt, giving expressions to predict hornblende-melt trace-element partitioning values. These expressions are used to show that heavy REE-enriched hornblende/whole-rock REE abundance patterns in granitoids may result from partial re-equilibration of hornblende and late-stage residual liquids rather than from anomalous partitioning values.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Hornblende-melt trace-element partitioning measured by ion microprobe
Series title Chemical Geology
DOI 10.1016/0009-2541(94)90135-X
Volume 117
Issue 1-4
Year Published 1994
Language English
Publisher Elsevier
Contributing office(s) Volcano Hazards Program
Description 14 p.
First page 331
Last page 344