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GrinchenkoО.V., Bondarenko S.M., Siomka V.O., Ivanov B.N., Kanunikova L.I. Composition оfТa-Nb mineralization in pegmatites and apograniticmetasomatites of Shpoliano-Tashlyk ore field. Geochemistry and ore formation. 2016. Vol. 36. p. 47-57.

Сomposition of Ta-Nb mineralization in rare-metal deposits and ore manifestations of the most perspective as to metallogenic aspect Shpoliano-Tashlyk ore field (central part of the Ukrainian Shield) is discussed. The main minerals concentrators of Ta and Nb in granite pegmatites and apograniticmetasomatites are mineral varieties of three isomorphic series: columbite-tantalite (Fe,Mn)(Nb,Ta,Ti)2O6, ilmenorutile-struverite (Ti,Nb,Ta)O2and pyrochlore-microlite (Ca,Na)2Ta2O6(O,B,OН,F). Depending on geological conditions such ore minerals as tapiolite, ixiolite, cassiterite, uraninite, nigerite and gahnite are commonly occurred in association with these minerals. By microprobe analysis chemical composition of columbite-tantalitite mineralogical group from ore-bearing pegmatites and metasomatites is investigated. For columbite-tantalite mineral aggregates the presence of characteristic internal rithmically altered zoning and distictmosaicity, that is closely associated with irregularities of their chemical compositions, are established. Within one aggregate phases with wide ranges of Ta2O5– from 9,80 to 71,0 % and Nb2O5 – from 10,6 to 70,1 % are found. Among minerals ferruous members which composition relates to Fe-columbite-tantalitam (Nb2O5/Ta2O5= 1–1,2; FeО/MnО = 2,5–6) prevail. Columbite-tantalites are characterised by high contents of admixutre-elements (%): TiО2– up to 5,88; WО3– up to 3,70; SnО2– up to 9,20; Sc2O3– 5,40. Scandiumbearing varieties are occurred to be predominantly columbite-tantalities from the Polohovka ore field. In Ukraine, such high Sc2O3contents in tantalo-niobitesare found for the first time. Minerals of ilmenorutile-struverite group do not quantatively concede to those of columbite-tantalite group. Some regional features of typochemistry for minerals of this group (Nb2O5/Ta2O5= 0,4–1,6) are established. Minerals of pyrochlore-microlite show considerably low distribution scale. The main features of ore mineralization in rare-metal pegmatites and apograniticmetasomatites, including such typomorphic features as Ta/Nb ratio and composition of addmixutures elements, have paragenetic relation with parent granites of S-type after which these ore-bearing apogranitic associations are formed.


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