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- 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.
- Time-space evolution of Iberian Pyrite Belt igneous activity: Volcanic and plutonic lineaments, geochronology, ore horizons and stratigraphic constraintsPublication . Albardeiro, Luís; Morais, Igor; Matos, João Xavier; Solá, A. Rita; Salgueiro, Rute; Pereira, Zélia; Mendes, Márcia; Batista, Maria Joao; de Oliveira, Daniel Pipa Soares; Diez-Montes, Alejandro; Inverno, Carlos; Pacheco, Nelson; Araújo, VítorABSTRACT: The volcanism in the Iberian Pyrite Belt migrated from the present day west/southwest to the east/northeast during Devonian/Carboniferous times. Evidence is here discussed based in U-Pb zircon ages of felsic volcanic and plutonic rocks, bounded by enclosed sediments and their biostratigraphic ages, together with hosted massive sulphides deposits and associated plutonic counterparts.Volcano-Sedimentary Complex rocks define several volcanic axes, or lineaments, with the general NWSE to WNW-ESE belt trending orientation. The usage of all the available data from high-resolution stratigraphy, geology and geophysics lead to establishment of eleven main volcanic axes, nine with zircon U-Pb radiometric ages (166 samples).In this research, we reinforce a previous inter-axes volcanic evolutionary trend, but we also suggest an intra-axis evolutionary trend of the IPB igneous activity with time. This means the basin igneous activity also evolved along most of the volcanic and plutonic lineaments, from west/northwest to east/southeast.Successive weighted average ages for each axis (SW to NE) and opposite end-point sample ages for each axis (NW/W to SE/E) are presented. Similar trends are found with felsic volcanic rocks, subvolcanic and plutonic rocks and even massive sulphide ages correspond to the regional trend corroborating the proposed geological framework.Siliciclastic sediments and lower VSC sequences (sediments, felsic volcanic rocks and massive sulphides) show a comparable age trending evolution although upper VSC sediments seem to be contemporaneous across the province. Older ages, from zircon U-Pb and from associated reworked palynomorph in the sediments, show a long-lasting age distribution along most Devonian times, suggesting the IPB evolved since Lochkovian times (Lower Devonian). Therefore, we propose the IPB inter-axes evolution could be related with a NE-direction plate motion (present-day location) over a heat source, while intra-axes are probably due to the collisional/compressive tectonic interaction of South Portuguese - Ossa-Morena zones tectonic setting.
- Biostratigraphic and structural research in the Guedelhinha–Lançadoiras–Algaré sector in the context of the geology of the Neves–Corvo mine region, Iberian Pyrite BeltPublication . Pereira, Zélia; Matos, João Xavier; Mendes, Márcia; Solá, A. Rita; Albardeiro, Luís; 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–Lançadoiras–Algaré 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 confirmed, 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.