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Title: The distribution of rare metals in the LCT pegmatites from the Giraúl Field, Angola
Author: Gonçalves, Antonio Olimpio
Melgarejo i Draper, Joan-Carles
Alfonso Abella, María Pura
Amores Casals, Sandra
Paniagua, Andrés
Neto, André Buta
Alves Morais, Eduardo
Camprubí, Antoni
Keywords: Pegmatites
Cendres volcàniques
Volcanic ash
Issue Date: 24-Sep-2019
Publisher: MDPI
Abstract: 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.
Note: Reproducció del document publicat a:
It is part of: Minerals, 2019, vol. 9, num. 10, p. 580-
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ISSN: 2075-163X
Appears in Collections:Articles publicats en revistes (Mineralogia, Petrologia i Geologia Aplicada)

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