DBPapers
DOI: 10.5593/sgem2017/11/S01.010

CHEMICAL CHARACTERISTICS OF REE-BEARING PHOSPHATE MINERALS FROM DÚRICO-BEIRÃO GOLD-ANTIMONY MINING DISTRICT (NORTHERN PORTUGAL)

H. Couto, G. Roger, Y. Moelo
Saturday 9 September 2017 by Libadmin2017

References: 17th International Multidisciplinary Scientific GeoConference SGEM 2017, www.sgem.org, SGEM2017 Conference Proceedings, ISBN 978-619-7105-98-8 / ISSN 1314-2704, 29 June - 5 July, 2017, Vol. 17, Issue 11, 81-88 pp, DOI: 10.5593/sgem2017/11/S01.010

ABSTRACT

Rare earth element (REE) resources are nowadays of great interest because of their importance as raw materials for high technology manufacturing, being also significant as geochemical indicators. Various phosphate mineral bearing rare-earth elements (REE) have been observed in the Dúrico-Beirã gold-antimony district (North Portugal). Besides apatite, the more abundant phosphate, xenotime, monazite and florencite were identified by scanning electron microprobe (SEM). They are usually associated to Palaeozoic metasediments, volcanics (namely associated to a rifting at the Cambrian–Ordovician transition) and plutonic rocks, as well as gold-antimony deposits. In xenotime disseminated within the Lower Ordovician succession of interbedded volcano-sedimentary layers with ironstones, dominant REE are Y, Dy, Er, Gd, Yb and Ho, with secondary Tb. In xenotime from Lower to Middle Ordovician phosphatic layers with lingulids, main REE are Y, Dy, Er and Yb with secondary Ho and Gd. This xenotime is enriched in heavier REE relatively to xenotime from ironstones, with intermediate REE (Gd and Tb). SEM analysis of monazite-(Ce) present in Cambrian volcanic rocks showed Ce, Nd, La, Pr, Y, Sm and Gd (in decreasing content), while monazite in the matrix of the conglomerates contains Ce, La, Nd, Y, Pr and Sm with traces of Th. Florencite-(Ce), present in the conglomerate matrix of Montalto Formation (Cambrian) and albitized granitoids from the Ribeiro da Serra Sb-Au mine, revealed Ce, Sr, Nd and La. REE distribution among phosphate minerals permits to discriminate geological formations as well as magmatic or hydrothermal processes at the scale of an ore district. The studied area fits among the Palaeozoic REE belts one of the main REE metallogenetic provinces in Europe.

Keywords: rare earth elements (REE), phosphates, gold-antimony deposits, igneous rocks, Palaeozoic metasediments.

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