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Vetorização de sulfuretos maciços vulcanogénicos: Moinho (Aljustrel), Faixa Piritosa Ibérica
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Orientador(es)
Resumo(s)
The Iberian Pyrite Belt (IPB) is a classical example of massive sulphide mineralization associated with volcanosedimentary sequences. The Aljustrel deposit stands out due to the number and diversity of mineralized bodies, as well as the high base-metal grades; however, the geology of the Moinho orebody is still insufficiently characterized. In order to improve the understanding of this orebody, a systematic characterization of the host rocks was carried out, with particular emphasis on the metavolcanic units of the Volcano-Sedimentary Complex (VSC). Four drill holes (PM16002, MM16022, MM23014 and MS10005), located at different distances from the central axis of the mineralized body, were studied, allowing for a comparative analysis. The re-logging, based on macroscopic, mineralogical, petrographic and geochemical criteria, as well as alteration patterns, and correlated with surface geological mapping (Matos, 2021), allowed the metavolcanic rocks to be regrouped into two main units: Va, productive and hosting massive sulphides, and Vap, barren. Lithologies external to the VSC were also recognized, namely metasedimentary rocks belonging to the Mértola Formation (GFBA). The integration of this information enabled the construction of interpretative geological cross-sections, refining the spatial distribution of the geological units and the geometry of the Moinho orebody, as well as updating the geological mapping used to support exploration activities. The geochemical separation between Va and Vap was based on immobile element ratios (Zr/Ti, Al/Ti, Zr/Y, La/Lu), revealing distinct signatures and suggesting two volcanic events. Subsequent hydrothermal processes generated chloritic–sericitic alteration in the Va unit and silicic–sericitic alteration in the Vap unit. The average alteration index (AI) and mineralization index (CCPI) values are 63 and 47 for Va, and 59 and 57 for Vap, respectively. The integration of trace-element geochemistry and two-dimensional geological cross-sections allowed the definition of the productive (Va) and barren (Vap) units. These criteria, already applied by the ALMINA team, constitute a local exploration vector and contribute to the understanding and optimization of the geological model of Aljustrel, particularly in the context of the Moinho orebody.
Descrição
Relatório de estágio de mestrado, Geologia (Geodinâmica e Recursos geológicos), 2025, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Aljustrel Moinho Geochemistry Petrogenetics Prospecting Vectors