Record details

Title
    Highly ordered, homogeneous ferrocolumbite from an anorogenic granitic pegmatite at Ivittuut (Ivigtut), SW Greenland
Statement of responsibility
    Milan Novák, Petr Černý
Author
    Černý, Petr
    Novák, Milan, 1952-
Language
    anglicky
Source title - serial
    Neues Jahrbuch für Mineralogie. Monatshefte
Vol./nr.
    H. 10
Pages
    p. 433-443
Year
    2000
Notes
    2 obr., 4 tab.
    il.
    Obsahuje bibliografické odkazy
    Zkr. název ser.: Neu. Jb. Mineral., Mh.
Subject group
    krystalizace
    ložisko kryolitu
    mřížkové parametry
    niob
    pegmatit
    skupina columbitu
    stupeň uspořádanosti
Geographical name
    Grónsko
Keyword
    Anorogenic
    Ferrocolumbite
    Granitic
    Greenland
    Highly
    Homogeneous
    Ivigtut
    Ivittuut
    Ordered
    Pegmatite
    SW
Abstract (in english)
   Accessory but widespread ferrocolumbite occurs in a coarse-grained microcline+quartz pegmatite overlying the ivigtut cryolite deposit, SW greenland. Euhedral crystals, up to 2 cm in size, are enclosed in microcline, locally in quartz, and overgrown by late cryolite. The crystals are commonly found loose, very likely due to weathering of th matrix. Associated minor and accessory minerals include sulphides (galena, sphalerite, chalcopyrite, molybdenite) and Nb-rich cassiterite (with Nb/Ta wt.=17.2-7.5). All ferrocolumbite samples studied are extremely homogeneous and have remarkably similar chemical compositions; the ratio Mn/(Mn+Fe)at. varies from 0.22 to 0.27, whereas Ta/(Ta+Nb)at. ranges from 0.004 to 0.02, and Nb/Ta wt.=46.1-25.1. Minor elements include Ti and W up to 0.14 apfu, Zn up to 0.06 apfu and Sn up to 0.02 apfu. The unit-cell dimensions indicate highly to fully ordered structure.
   The very high Nb/Ta ratio and homogeneity of ferrocolumbite seem to be caused by very low activity of Ta relative to Nb in the parent (possibly mantle-derived) melt; and by near-equilibrium crystallization
Contributor
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
    U
Entered date
    11. 12. 2006
Import date
    8. 8. 2012