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que engloba grande parte do território alentejano, é uma zona paleogeográfica do território nacional. A sua complexa evolução geológica faz com que esta zona apresente uma riqueza significativa no que diz respeito à ocorrência de uma diversidade de matérias-primas, contendo 13 das 27 matérias-primas críticas presentes na lista definida pela União Europeia (não obstante as suas baixas tonelagens), para além de matérias-primas estratégicas como o ouro ou a prata. No presente trabalho, introduz-se os critérios utilizados para a definição de criticidade das matérias-primas, assim como a sua distribuição em Portugal, dando especial enfase às matérias-primas identificadas na Zona de Ossa-Morena.

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<p>In SW Iberia (namely in the northernmost domains of Ossa-Morena Zone [OMZ]), NW-SE lineaments of peralkaline igneous massifs are found, known to have been emplaced during the Cambrian-Ordovician rift-related magmatic stage of the Variscan extension in northern Gondwana. In the Portuguese counterpart of the OMZ, these rocks can be found in two distinct tectono-stratigraphic segments, namely the Blastomylonitic Belt (BB) and in the Alter do Chão – Elvas Sector (ACES), intruding Neoproterozoic to Middle Cambrian successions (further extending to the Spanish side). Though the peralkaline magmas are coeval, some contrasting geochemical features allow a well-marked distinction between rocks located in the BB and ACES, which may provide sustained inferences on the petrogenesis and geotectonic framework. The BB rocks composition fit within the phonolite-trachyte spectrum, and show affinities with “within-plate” and A1-type granitoids. On the other hand, rocks from the ACES display trachyte to alkaline rhyolite compositions, chemical features of A2-type granitoids and “anomalous ocean ridge granite” tectonic setting of emplacement. However, within the ACES there are exceptions, as three massifs appear to have the same chemical signatures of the BB. Lithogeochemical data suggest the Ossa-Morena Zone alkaline melts (i) could be extracted from distinct sources, and/or (ii) underwent different degrees of fractionation along with variable crustal assimilation. In addition to lithogeochemistry data, further mineralogical and isotopic studies will be addressed to better understand and provide sustained inferences on the development of the northern OMZ peralkaline magmatism and related ore-forming systems.</p><p>Acknowledgements: JR acknowledges the financial support provided by Fundação para a Ciência e Tecnologia (FCT) through the PhD grant (UI/BD/150937/2021), and by the Society of Economic Geologists Foundation through the Hugh McKinstry Fund. The authors also acknowledge expenses supported by ICT financed by FCT, under the project UIDB/04683/2020. This work is a contribution to the project “ZOM-3D Metallogenic Modelling of Ossa-Morena Zone: Valorization of the Alentejo Mineral Resources” (ALT20-03-0145- FEDER-000028), funded by Alentejo 2020 through the FEDER/FSE/FEEI.</p>