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- Late Famennian (latest Strunian) palynomorph assemblages and their role in the Neves Formation depositional environment -The Neves-Corvo mine case study (Iberian Pyrite Belt, Portugal)Publication . Mendes, Márcia; Pereira, Zélia; Matos, João Xavier; Albardeiro, Luis; Morais, Igor; Araújo, VitorABSTRACT: This research examines palynomorph assemblages preserved in sediments of the Iberian Pyrite Belt (IPB) that host the Neves-Corvo massive sulfide deposit and its importance for mineral exploration. The sediments belong to the Neves Formation, characterized by black shales and minor occurrences of siltstones and cherts, indicative of reduced environmental conditions, favorable to sulfide deposition in a hydrothermal context dominated by submarine felsic volcanism and graben structures. Analysis was performed in barren drill holes (e.g., Monte Novo), as opposed to productive sectors with massive sulfide mineralization and/or stockwork vein networks (e.g., Lombador, Corvo and Semblana deposits) and favorable sectors like Algar & eacute;. The recovered palynological assemblages are assigned to the LN Miospore Biozone, indicating a Late Famennian (latest Strunian) age. Several characteristic species of this age are identified, such as Retispora lepidophyta and Verrucosisporites nitidus in close association with Densosporites spitbergensis, Dictyotriletes fimbriatus, Retusotriletes cf. incohatus, Retusotriletes crassus, Vallatisporites spp. (including V. pusillites, and V. verrucosus). ) . Despite some palynomorphs showing signs of breakage, folding, and indistinctness, no significant preservation or diversity differences were noted between barren and mineralized areas. The high abundance of marine phytoplankton in all studied black shales indicates ecologically stressed setting, dominated by dysoxic to anoxic conditions in a distal marine setting with active felsic volcanism and hydrothermal mineralizing events during Late Famennian time. This geologic context correlates with other IPB deposits and the global latest Devonian anoxic Hangenberg event.
- Biostratigraphic and structural research of the Guedelhinha-Lançadoiras- Algaré sector of the Neves-Corvo mine region, Iberian Pyrite BeltPublication . Pereira, Zélia; Matos, João Xavier; Mendes, Márcia; Solá, A. Rita; Albardeiro, Luís; Morais, Igor; Araújo, Vítor; Pacheco, Nelson; Oliveira, José TomásABSTRACT: Based on drill hole sampling and sedimentary rock dating by palynology, the present research focuses on the palynostratigraphic events established in the key geological section of Guedelhinha-Lancadoiras-A lgare located in the Portuguese Neves-Corvo mine region, Iberian Pyrite Belt. The age data allow detailing the lithostratigraphic sequence and further understanding the complex structural setting, representing an important contribution to the geological knowledge of this sector located to the immediate WNW of the Neves-Corvo VMS deposit. The combination of the studied events allows the reconstruction of the Devonian-Carboniferous sedimentation and paleoenvironments along the Iberian Pyrite Belt. Several stratigraphic hiatuses identified in the Neves-Corvo region by the palynological record are con-firmed, mainly occurring from the mid Frasnian to mid Famennian, from the early and mid Strunian, and from the early to late Tournaisian, which were mainly coincident with the worldwide extinction events, in particular during Frasnian-Famennian and Late Devonian times. Extensional tectonics and related gravitational faults, local uplift mechanisms and intense volcanic activity could also explain the lack of palynological data and sedimentary hiatus. In this research, the importance of the late Strunian times in the Iberian Pyrite Belt (Miospore Biozone LN of the Neves Formation) is highlighted, confirming the contemporaneity of felsic volcanism, hydrothermalism, sulphide mineralization precipitation and black shale anoxic sedimentation.
- Biostratigraphic and structural research of the Guedelhinha-Lançadoiras- Algaré sector of the Neves-Corvo mine region, Iberian Pyrite BeltPublication . Pereira, Zélia; Matos, João Xavier; Mendes, Márcia; Solá, A. Rita; Morais, Igor; Albardeiro, Luís; Araújo, Vítor; Pacheco, Nelson; Oliveira, José TomásSUMÁRIO: A presente investigação mostra os principais eventos palinoestratigráficos identificados na seção geológica de Guedelhinha-Lançadoiras-Algaré, localizada na região da mina de Neves-Corvo, Faixa Piritosa Ibérica. A idade estabelecida permitiu detalhar a sequência litoestratigráfica e compreender a grande complexidade estrutural, representando um importante contributo para o conhecimento geológico deste sector. A sequência de eventos reconhecida possibilitou a reconstrução da sedimentação e dos paleoambientes durante o Devónico e Carbónico, confirmando a existência de vários hiatos identificados na região da mina de Neves-Corvo. Salienta-se a importância dos sedimentos de idade Estruniano superior na Faixa Piritosa Ibérica (Biozona de Miosporos LN; Formação de Neves), confirmando a contemporaneidade entre o vulcanismo félsico, hidrotermalismo e precipitação de sulfuretos metálicos e a sedimentação anóxica de xistos negros.
- Geology of the recently discovered massive and stockwork sulphide mineralization at Semblana, Rosa Magra and Monte Branco, Neves–Corvo mine region, Iberian Pyrite Belt, PortugalPublication . Pereira, Zélia; Matos, João Xavier; Solá, A. Rita; Batista, Maria Joao; Salgueiro, Rute; Rosa, Carlos; Albardeiro, Luis; Mendes, Márcia; Morais, Igor; de Oliveira, Daniel Pipa Soares; Pacheco, Nelson; Araújo, Vítor; Castelo Branco, José M.; Neto, Rodrigo; Lains Amaral, João; Inverno, Carlos; Oliveira, José T.Abstract The recently discovered massive and stockwork sulphide mineralization of Semblana-Rosa Magra and Monte Branco, situated ESE of the Neves–Corvo volcanogenic massive sulphide (VMS) deposit in the Iberian Pyrite Belt (IPB) is presented. Geological setting and tectonic model is discussed based on proxies such as palynostratigraphy and U–Pb zircon geochronology. The mineralization is found within the IPB Volcano-Sedimentary Complex (VSC) Lower sequence, which includes felsic volcanic rocks (rhyolites) with U–Pb ages in zircons of 359.6 ± 1.6 Ma, and black shales of the Neves Formation of late Strunian age. Massive sulphides are enveloped by these shales, implying that felsic volcanism, mineralization and shale sedimentation are essentially coeval. This circumstance is considered highly prospective, as it represents an important exploration vector to target VMS mineralization across the IPB, in areas where the Lower VSC sequence is present. The Upper VSC sequence, with siliciclastic and volcanogenic sedimentary rocks of middle–late Visean age, shows no massive mineralization but a late Tournaisian (350.9 ± 2.3 Ma) volcanism with disseminated sulphides was also identified. Nevertheless, stratigraphic palynological gaps were found within the Strunian and in the Tournaisian sediments, between the Lower and Upper VSC sequences, reflecting probable erosion and uplift mechanisms linked with extensional tectonics. The Semblana and Monte Branco deposits and the Rosa Magra stockwork are enclosed by tectonic sheets that dismembered the VSC sequence in a fold-and-thrust tectonic complex, characteristic of the NE Neves–Corvo region. The methodologies used allow a geological comparison between Neves–Corvo and other IPB mine regions such as Lousal–Caveira, Herrerias, Tharsis and Aznalcollar.