Browsing by Author "Diez-Montes, Alejandro"
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- The state of the art of Phyllite-Quartzite Group Lower and Upper sequences, Mid-Late Devonian siliciclastic basinPublication . Matos, João Xavier; Pereira, Zélia; Mendes, Márcia; Albardeiro, Luís; Diez-Montes, Alejandro; Araújo, Vítor; Oliveira, José TomásRESUMO: O Grupo Filito-Quartzítico (GFQ) é considerado o substrato siliciclástico da Faixa Piritosa Ibérica (FPI), aflorando nas antiformas de Pomarão-Puebla de Guzmán, Valverde, Neves-Corvo– Rosário, Lousal–Caveira, São Francisco da Serra e Cercal. No setor norte da FPI o GFQ está presente em estruturas alóctones em São Domingos, Mértola, Alcaria Ruiva, São Barão, Roxo e Serrinha. A idade palinológica do GFQ, a cartografia geológica e a informação de sondagens de prospeção, permitem definir duas sequências principais: GFQ Inferior (base desconhecida e idade Givetiano a Frasniano, Biozonas de Miosporos AD Lem e BH) e GFQ Superior (idade Famenniano superior, Biozonas de Miosporos VCo, VH e LN). A sequência GFQ superior tem uma idade contemporânea da Sequência Inferior do Complexo Vulcano-Sedimentar da FPI e início da formação dos depósitos de sulfuretos maciços vulcanogénicos (p.e., jazigos Neves-Corvo, Lousal e Caveira de idade Estruniano).
- 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.