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Niobium-tantalum minerals in the Skoddefjellet NYF granitic pegmatite, Svalbard Archipelago, Norway: Primary versus secondary assemblage
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
2010 (English)In: Neues Jahrbuch für Mineralogie - Abhandlungen, ISSN 0077-7757, Vol. 187, no 3, 235-248 p.Article in journal (Refereed) Published
Abstract [en]

The first documented occurrence of Nb-Ta mineralization in a granitic pegmatite from the Svalbard Archipelago, Arctic Caledonides and the relationships between primary and secondary Nb, Ta-bearing phases are discussed. The Skoddefjellet NYF pegmatite located in southwest Spitsbergen (Wedel Jarlsberg Land) is characterized by enrichment in Nb, U, Zr, Y, REE and Pb, low Zr/Hf (similar to 8-10), and (similar to 8-12) Nb/Ta ratios. Columbite-(Fe) and columbite-(Mn) (locally enriched in Ti, Y, Sc and Ca) and Nb, Ta, Y-bearing titanite (<= 3.8 wt. % Nb2O5, <= 1.9 wt. % Ta2O5, <= 2.9 wt. % Y2O3) represent the primary magmatic Nb-Ta minerals. The secondary assemblage comprises Nb,Ta-bearing rutile (<= 23 wt. % Nb2O5, <= 1.7 wt. % Ta2O5), ilmenite, fersmite and pyrochlore group minerals: including yttropyrochlore-(Y), plumbopyrochlore, yttrobetafite-(Y) and plumbobetafite. Internal zoning of columbite group minerals is expressed by distinct rimward increase of the Mn/(Mn+Fe) ratio (0.07 to 0.83) and low Ta/(Ta+Nb) ratio (0.03 to 0.10), suggesting alkaline environment and increasing fluorine activity during the pegmatite evolution. The formation of secondary phases is related to the hydrothermal stage of the pegmatite. Notably, the formation of Nb, Ta-bearing rutile and ilmenite seems to be a product of Nb, Ta-bearing titanite alteration.

Place, publisher, year, edition, pages
2010. Vol. 187, no 3, 235-248 p.
Keyword [en]
Nb-Ta oxide minerals, columbite, Nb, Ta-rich titanite, Ta-rich rutile, ilmenite, pyrochlore-group minerals, fersmite, NYF granitic pegmatite, Spitsbergen
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-134676DOI: 10.1127/0077-7757/2010/0172ISI: 000282322900001OAI: oai:DiVA.org:uu-134676DiVA: diva2:373645
Available from: 2010-12-01 Created: 2010-11-30 Last updated: 2011-02-02Bibliographically approved

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