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Open AccessArticle

The Distribution of Rare Metals in the LCT Pegmatites from the Giraúl Field, Angola

1
Departamento de Geologia, Faculdade de Ciências, Universidade Agostinho Neto, Av. 4 de Fevreiro 71, Caixa Postal 815, Luanda 2131, Angola
2
Departament de Mineralogia, Petrologia i Prospecció Geològica, Facultat de Ciències de la Terra, Universitat de Barcelona, Carrer de Martí i Franquès s/n, 08028 Barcelona, Spain
3
Departament d’Enginyeria Minera, Industrial i TIC, Universitat Politècnica de Catalunya, Avinguda de les Bases de Manresa 61–73, 08242 Manresa, Spain
4
Departamento de Ciencias de la Tierra, Universidad de Zaragoza, Calle Pedro Cerbuna 12, 50009 Zaragoza, Spain
5
Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510 Coyoacán, Mexico
*
Author to whom correspondence should be addressed.
Minerals 2019, 9(10), 580; https://doi.org/10.3390/min9100580
Received: 29 August 2019 / Revised: 22 September 2019 / Accepted: 23 September 2019 / Published: 24 September 2019
(This article belongs to the Special Issue Mineral Deposits of Critical Elements)
The Giraúl granitic pegmatite field in Angola is composed of five pegmatite types, the most evolved belong to the beryl-columbite, beryl-columbite-phosphate and spodumene types. Pegmatites are concentrically zoned with increased grain size toward a quartz core; the most evolved pegmatites have well-developed replacement units. These pegmatites are rich in Nb-Ta oxide minerals and the field has a moderate interest for critical elements such as Ta and Hf. Tourmaline, garnet and micas occur as accessory minerals. The abundance of Zr and Nb-Ta minerals increases with the evolution of the pegmatites, as well as the proportions of beryl and Li-rich minerals. The Ta/(Ta + Nb) ratio in Nb-Ta oxide minerals and the Hf/(Hf + Zr) ratio in zircon also increase with the evolution of the pegmatites and within each pegmatite body from border to inner zones, and especially in the late veins and subsolidus replacements. Textural patterns and occurrence of late veins with Ta-rich minerals suggest that Nb and especially Ta can be enriched in late hydrothermal fluids exsolved from the magma, along with Hf and other incompatible elements as Sn, U, Pb, Sb and Bi. View Full-Text
Keywords: pegmatites; columbite-group minerals; pyrochlore supergroup; niobium; tantalum; beryllium; hydrothermal; Angola pegmatites; columbite-group minerals; pyrochlore supergroup; niobium; tantalum; beryllium; hydrothermal; Angola
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Gonçalves, A.O.; Melgarejo, J.-C.; Alfonso, P.; Amores, S.; Paniagua, A.; Neto, A.B.; Morais, E.A.; Camprubí, A. The Distribution of Rare Metals in the LCT Pegmatites from the Giraúl Field, Angola. Minerals 2019, 9, 580.

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