Trace-element partitioning between synthetic potassic-richterites and silicate melts, and contrasts with the partitioning behaviour of pargasites and kaersutites

Massimo Tiepolo*, Alberto Zanetti, Roberta Oberti, Richard Brumm, Stephen Foley, Riccardo Vannucci

*Corresponding author for this work

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Solid/liquid partition coefficients for large ion lithophile elements (Ba, Rb, Sr), high field strength elements (Zr, Hf, Nb, Ta, Ti), rare earth elements (La-Yb), Pb, Th, U and selected transition elements (Sc, V) were determined by means of Secondary Ion Mass Spectrometry on potassic-richterites synthesised at upper mantle conditions (P = 1.4 GPa and T = 850-1020°C) from silica-rich lamproites. Most trace elements display an incompatible behaviour in potassic-richterites; only Sr, Ti, Sc and V show strong positive anomalies in the partitioning pattern. When S/LD for potassic-richterites are compared with those for calcic amphiboles (pargasites and kaersutites) several differences become evident. In general, S/LD are lower in potassic-richterites; also, different partitioning patterns are apparent for RE and LIL elements. These differences are discussed in terms of the distinct crystal-chemical behaviour of the involved amphibole end-members, with particular emphasis to the available charge-balance mechanisms and to the site dimensional constraints ruling incorporation of trace elements in the various sites. The distinct partitioning behaviours of trace elements in potassic-richterites and pargasites and kaersutites imply that melts produced from amphibole-bearing sources may differ markedly depending on the type of amphibole crystallised. Therefore, the new partitioning data are used to discuss the role of potassic-richterite in its principal modes of occurrence, namely in lamproites, in peralkaline ultramafic veins in the lithospheric mantle, and in the deeper parts of subduction zones.

Original languageEnglish
Pages (from-to)329-340
Number of pages12
JournalEuropean Journal of Mineralogy
Volume15
Issue number2
DOIs
Publication statusPublished - Mar 2003
Externally publishedYes

Keywords

  • Alkaline rocks
  • Amphibole
  • Experimental petrology
  • Partition coefficients
  • Potassic-richterite
  • Trace elements

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