Szczegóły publikacji
Opis bibliograficzny
The euxenite-group minerals and products of their alteration in the hybrid Julianna granitic pegmatite Piława Górna, Sudetes, Southwestern Poland / Adam Szuszkiewicz, Adam PIECZKA, Eligiusz Szełęg, Krzysztof Turniak, Sławomir Ilnicki, Krzysztof Nejbert // The Canadian Mineralogist ; ISSN 0008-4476. — 2016 — vol. 54 no. 4, s. 879–898. — Bibliogr. s. 895–898, Abstr.
Autorzy (6)
- Szuszkiewicz Adam
- AGHPieczka Adam
- Szełęg Eligiusz
- Turniak Krzysztof
- Ilnicki Sławomir
- Nejbert Krzysztof
Słowa kluczowe
Dane bibliometryczne
| ID BaDAP | 111133 |
|---|---|
| Data dodania do BaDAP | 2018-01-15 |
| DOI | 10.3749/canmin.1600023 |
| Rok publikacji | 2016 |
| Typ publikacji | artykuł w czasopiśmie |
| Otwarty dostęp |  |
| Czasopismo/seria | Canadian Mineralogist |
Abstract
Polycrase-(Y) and euxenite-(Y) represent the euxenite- group minerals (EGM) that formed as magmatic minerals in the sequence of (Y, REE,U,Th)-(Nb,Ta,Ti) oxides: columbite-(Fe) -> Ti-bearing ixiolite +/- ferrowodginite -> samarskite-group minerals [ishikawaite -> samarskite-(Y)] -> EGM in the moderately fractionated granitic pegmatites of the hybrid NYF + LCT Julianna pegmatitic system at Pilawa Gorna, Sudetes, SW Poland. The EGM crystallized with increasing Ti activity and decreasing Ta/(Ta + Nb) and Mn/(Mn + Fe) from F-poor and LREE-depleted melt. The variation in their composition results mainly from substitution along the (A)(U,Th)Ti-B(A)(Y,REE)(-1)(B)(Nb,Ta)(-1) vector. Metasomatic alteration of the EGM resulted in the formation of a variety of secondary pyrochlore supergroup minerals (PSM). The chemical composition of the PSM depends on the access gained by the metasomatic fluid to the replacement front. Alteration at sites of restricted access of the fluid led first to the formation of atypical Ca-enriched EGM evolving to zero-valence-dominant betafite with Y + REE as the second-rank A-site component, and finally to (Y, REE)- rich zero-valence-dominant pyrochlore. These PSM closely reflect the compositions of the parental EGM as indicated by similar Ti/(Ti + Ta + Nb), Ta/(Ta + Nb), and Mn/(Mn + Fe) values. If the transport of ions to and from the replacement front was relatively easy, the compositions of the alteration products were less limited by the composition of the primary oxides and zero-valence-dominant pyrochlore with Ca or U + Th as the second-rank A-site components formed. This type of alteration took place with decreasing Ti/(Ti + Nb + Ta), Y/(Y + REE), and Mn/(Mn + Fe) but highly variable Ta/(Ta + Nb). The addition of Ca, Fe, Mg, Sn, and Pb to the pegmatitic system during metasomatic alteration of the EGM could have been achieved through: (1) reaction of the orthomagmatic fluid with the amphibolite wall rock, circulating in a convective cell around the pegmatites; (2) assimilation of the wall rock by the pegmatite-forming melt; or (3) autometasomatic processes. However, given the current state of knowledge about the geochemical evolution of the Julianna pegmatitic system, the first scenario seems most likely.