Rare Earth Element-Bearing Tausonite and Potassium Barium Titanates from the Little Murun Potassic Alkaline Complex, Yakutia, Russia

Roger H. Mitchell and Nikolai V. Vladykin
Department of Geology, Lakehead University, Thunder Bay, Ontario, Canada P7B 5E1
Institute of Geochemistry, Academy of Sciences, P.O. Box 4019, Irkutsk-33, Russia 664033

Abstract: Tausonites occurring in aegirine potassium feldspar syenite from the Little Murun potassic alkaline complex are characterised by complex growth and resorption features. These are attributed to non-equilibrium crystallisation in a dynamic environment characterised by magma mixing and/or volatile degassing. The crystals represent a transported assemblage which has no simple relationship to the magma from which their host rock crystallised. Tausonites exhibit significant normal, reverse and oscillatory compositional zoning with respect to strontium and the rare earth elements. The compositions are unique, ranging from tausonite to strontian cerian loparite, and are unlike those found in strontian perovskites from lamproites and fenites associated with carbonatites.

Compositional data are presented for Ba-rich titanates belonging to the hollandite group, Ba(Ti,Fe)5O11 and K2Ti13O27. The titanates, on the basis of textural evidence, are interpreted to have formed by the reaction of K-Ba-rich residual liquids with pre-existing Ti-magnetite, ilmenite and tausonite. The compositions of the titanates are similar to those of primary titanates found in kimberlites and carbonatites.

Keyword: tausonite • titanates • alkaline complex • Yakutia • Russia

Mineralogical Magazine; December 1993 v. 57; no. 389; p. 651-664; DOI: 10.1180/minmag.1993.057.389.09
© 1993, The Mineralogical Society
Mineralogical Society (www.minersoc.org)