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@article{490079,
author = {Novák, Milan and Černý, Petr and Uher, Pavel},
article_location = {Stuttgart},
article_number = {5},
keywords = {Extreme variation and apparent reversal of Nb-Ta fractionation in columbite-group minerals from the Scheibengraben beryl-columbite pegmatite; Maršíkov; Czech Republic},
language = {eng},
issn = {0935-1221},
journal = {European Journal of Mineralogy},
title = {Extreme variation and apparent reversal of Nb-Ta fractionation in columbite-group minerals from the Scheibengraben beryl-columbite pegmatite, Maršíkov, Czech Republic},
volume = {15},
year = {2003}
}
TY - JOUR
ID - 490079
AU - Novák, Milan - Černý, Petr - Uher, Pavel
PY - 2003
TI - Extreme variation and apparent reversal of Nb-Ta fractionation in columbite-group minerals from the Scheibengraben beryl-columbite pegmatite, Maršíkov, Czech Republic
JF - European Journal of Mineralogy
VL - 15
IS - 5
SP - 565-574
EP - 565-574
SN - 09351221
KW - Extreme variation and apparent reversal of Nb-Ta fractionation in columbite-group minerals from the Scheibengraben beryl-columbite pegmatite
KW - Maršíkov
KW - Czech Republic
N2 - Compositional variation in columbite-group minerals was studied from the beryl-columbite pegmatite at Scheibengraben, Maršíkov, Northern Moravia, Czech Republic. The pegmatite consists of five textural-paragenetic units, from the least to the most evolved: volumetrically dominant coarse-grained unit, subordinate graphic and blocky units and a minor cleavelandite unit. Saccharoidal albite unit is rather randomly distributed within the dike. It replaces and/or crosscuts all other units except the cleavelandite unit. Columbite-group minerals are the dominant Nb,Ta-oxide phases in all units. They are associated with other Nb,Ta-oxide minerals: minerals of the pyrochlore subgroup and fersmite in the coarse-grained unit, and minerals of the microlite subgroup, ferrotapiolite and rynersonite in the cleavelandite unit. The extreme Nb-Ta [Ta/(Ta+Nb) = 0.06 to 0.97 (microlite 0.99)] and appreciable Fe-Mn [Mn/(Mn+Fe) = (ferrotapiolite 0.22) 0.35 to 0.90] fractionations in columbite-group minerals differ from those observed in beryl pegmatites examined to date, but they are comparable with those in some highly fractionated, complex, Li-rich pegmatites. High activity of F (facilitated by low contents of B, P and Li in the pegmatite melt) very likely maximized such an extensive Nb-Ta fractionation, over and above differential solubilities of columbite and tantalite in pegmatite melt. The apparent reversal of Nb-Ta and Fe-Mn fractionation found in columbite from the saccharoidal albite unit seems to be an artefact from early units (particularly the coarse-grained one), which were extensively replaced by saccharoidal albite.
ER -
NOVÁK, Milan, Petr ČERNÝ a Pavel UHER. Extreme variation and apparent reversal of Nb-Ta fractionation in columbite-group minerals from the Scheibengraben beryl-columbite pegmatite, Maršíkov, Czech Republic. \textit{European Journal of Mineralogy}. Stuttgart, 2003, roč.~15, č.~5, s.~565-574. ISSN~0935-1221.
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