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Nb/Ta, Zr/Hf and REE fractionation in exotic pegmatite from the Keivy province, NW Russia, with implications for rare-metal mineralization in alkali feldspar granite systems

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dc.abstract.enThe White Tundra pegmatites are associated with the Keivy alkali feldspar granite complex in the Kola Peninsula, NW Russia. The host granites are aegirine-arfvedsonite, biotite-arfvedsonite and biotite-ferrohastingsite varieties, ranging compositionally from peralkaline through metaluminous to peraluminous. The pegmatites are remarkable for the diversity of the rare-metal mineralization. The inferred crystallization sequence of the main REE, HFSE and Ti minerals in the pegmatite is: zircon – fergusonite-(Y) – monazite-(Ce) – gadolinite-hingganite series – britholite-(Y) – astrophyllite – titanite – allanite-(Ce) –– chevkinite-(Ce) – ilmenite – kainosite-(Y) – REE carbonates. The pegmatites show unusual parageneses indicating a transition of the mineral associations from agpaitic to miaskitic in the same body (e.g. zirconosilicate → zircon; astrophyllite → titanite). A number of minerals have anomalous minor element contents. Astrophyllite and some titanites have low (even < 1) Nb/Ta and Zr/Hf ratios that contrast with the overall geochemical environment (ratios ≫ 1); titanite with very high Y and HREE contents; elevated Sn, W and V contents in some titanosilicates; allanite-(Ce) with very high Ti contents coupled with low (less than stoichiometric) values of Al, suggesting a Ti → Al substitution. Whole-rock compositions of the host granite show a steady decrease of Nb/Ta and Zr/Hf ratios in peralkaline through metaluminous to peraluminous types. Compositions of Ti minerals suggest that further fractionation of Nb-Ta, Zr-Hf and REE in the White Tundra exotic pegmatite and the crystallization of Ti minerals with anomalous compositions are due to a combination of several factors: assimilation by the primary magma (enriched in Zr, Nb, REE) of upper crustal lithologies enriched in Ta, Hf, LREE, W, Sn; consumption of significant amounts of Nb and Zr by early-crystallized pegmatitic fergusonite and zircon with Nb/Ta and Zr/Hf ≫ 1; transition of HFSE mineral assemblages in pegmatite from agpaitic to miaskitic with consequent lowering of Nb/Ta and Zr/Hf; crystallization of minerals in a low-temperature (hydrothermal) environment with changing F contents, that promoted a sporadic further decrease of Nb/Ta and Zr/Hf (to values < 1) and increase of Y + HREE. The implications of the fractionation mechanisms for ore-forming processes related to rare-metal granites are discussed.
dc.affiliationUniwersytet Warszawski
dc.contributor.authorJokubauskas, Petras
dc.contributor.authorBagiński, Bogusław
dc.contributor.authorMacdonald, Ray
dc.contributor.authorZozulya, Dmitry
dc.date.accessioned2024-01-25T13:31:20Z
dc.date.available2024-01-25T13:31:20Z
dc.date.issued2022
dc.description.financePublikacja bezkosztowa
dc.description.volume143
dc.identifier.doi10.1016/J.OREGEOREV.2022.104779
dc.identifier.issn0169-1368
dc.identifier.urihttps://repozytorium.uw.edu.pl//handle/item/113447
dc.identifier.weblinkhttps://api.elsevier.com/content/article/PII:S0169136822000877?httpAccept=text/xml
dc.languageeng
dc.pbn.affiliationearth and related environmental sciences
dc.relation.ispartofOre Geology Reviews
dc.relation.pages104779
dc.rightsClosedAccess
dc.sciencecloudnosend
dc.subject.enAstrophyllite
dc.subject.enTitanite
dc.subject.enFerriallanite
dc.subject.enPegmatite
dc.subject.enAlkali feldspar granite
dc.subject.enREE, Nb/Ta, Zr/Hf fractionation
dc.subject.enRare-metal deposits
dc.subject.enKeivy
dc.subject.enNW Russia
dc.titleNb/Ta, Zr/Hf and REE fractionation in exotic pegmatite from the Keivy province, NW Russia, with implications for rare-metal mineralization in alkali feldspar granite systems
dc.typeJournalArticle
dspace.entity.typePublication