Record details

Title
    Scandium substitution in columbite-group minerals and ixiolite
Statement of responsibility
    Michael A. Wise, Petr Černý, Alexander U. Falster
Other titles
    Granitic pegmatites: The Černý - Foord volume (Variant.)
Author
    Černý, Petr
    Falster, Alexander U.
    Wise, Michael A.
Language
    anglicky
Source title - serial
    Canadian mineralogist
Vol./nr.
    Vol. 36, no. 2
Pages
    p. 673-680
Year
    1998
Notes
    4 obr., 5 tab., 26 bibl.
    Francouzské resumé
    il.
    Zkr. název ser.: Canad. Mineralogist
Subject group
    chemismus minerálů
    cín
    frakcionace chemická
    krystalochemie
    oxidy
    pegmatit
    skandium
    skupina columbitu
    substituce
    titan
Geographical name
    Bradlo (Jihlava)
    Cínovec (Teplice)
    Cyrilov (Žďár nad Sázavou)
    Česká republika
    Kanada
    Kosov (Jihlava)
    Madagaskar
    Maršíkov (Šumperk)
    Mozambik
    USA
    Velká Británie-England
    Věžná (Žďár nad Sázavou)
Keyword
    Columbite-group
    Ixiolite
    Minerals
    Scandium
    Substitution
Abstract (in english)
   Columbite-group minerals and ixiolite with extremely variable concentrations of scandium are widespread in moderately to highly fractionated rare-element granitic pegmatites. Columbite-group minerals with 1-3 wt. per cent Sc2O, are referred to as scandian columbite - tantalite and show degrees of structural order similar to columbite - tantalite lacking Sc. Disordered structures remain orthorhombic and become ordered upon heating. Pseudo-orthorhombic stannian (Sn-rich), titanian (Ti) and wolframian (W) variants of ixiolite may contain as much as 3.7 wt. per cent Sc2O3 and revert to monoclinic phases upon heating. Similarly, scandian ixiolite that contains Sc in excess of 3.0 and up to 18.8 wt. per cent Sc2O3 converts from orthorhombic to monoclinic symmetry upon heating and has a stoichiometry that approaches Sc(Nb,Ta)O4. Scandium-bearing columbite -tantalite and ixiolite show similar ranges in Mn/(Mn + Fe) and Ta/(Ta + Nb) values, but noticeably different Sn, Ti and Sc contents.
   Scandium is incorporated into the columbite and ixiolite structures via the coupled substitution Sc3+ + (Ti,Sn)4+ = (Fe,Mn)2+ + (Nb,Ta)5+; it is strongly partitioned into the (Fe,Mn) site, whereas the Ti and Sn prefer the (Nb.Ta) site. Within the (Fe,Mn) site, the substitution of Sc for Fe is more prevalent. In most pegmatites, Sc fractionation in columbite - tantalite, stannian ixiolite, titanian ixiolite and wolframian ixiolite is erratic, unlike scandian ixiolite, which shows strong enrichment in Sc with increasing Mn, Ta and Sn
Contributor
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
    U
Entered date
    26. 9. 2007
Import date
    8. 8. 2012