Loading...
47 results
Search Results
Now showing 1 - 10 of 47
- Geological correlation of Neves-Corvo Mine and Pomarão Antiform sequences (Iberian Pyrite Belt, Portugal)Publication . Albardeiro, Luís; Matos, João Xavier; Mendes, Márcia; Solá, A. Rita; Pereira, Zélia; Morais, Igor; Salgueiro, Rute; Pacheco, Nelson; Araújo, Vítor; Oliveira, José TomásABSTRACT: A geological correlation between Neves-Corvo (NC) and Pomarão antiforms is attempted. These regional scale major sequences are easily correlated but, at local scale, facies and age differences stand out. Stratigraphy includes: i) the Phyllite-Quartzite Group with identical paleogeography setting and similar late Famennian ages for uppermost levels (LL to LN miospore biozones in Pomarão and NC respectively). ii) the Volcano-Sedimentary Complex shows some discrepancyconcerning the age distribution of the felsic volcanic rocks (ca. 356-330for Pomarão and ca. 365-346 Ma for all NC area) while sediments rangefrom mid-Famennian to late Visean age (VH to NM Miospore Biozonefor NC). iii); the Baixo Alentejo Flysch Group (late Visean NM MiosporeBiozone onwards in NC), covering the previous sequences and beingslightly older than the uppermost volcanic rocks of Pomarão. Thecorrelation between these two structures is supported by geology andisotopic/biozone ages and favours exploration scenarios in both regions.
- Preliminary dating of the Vale de Parreiras Formation of the late Famennian age, Iberian Pyrite Belt, Portugal, based on palynomorphsPublication . Mendes, Márcia; Pereira, Zélia; Albardeiro, Luís; Matos, João XavierABSTRACT: New palynostratigraphic data were obtained from phyllites interbedded with quartzwackes of the Vale de Parreiras Formation, located to the south of the Grândola Fault in the Azinheira de Barros region, Portugal. The studied outcrops are located in the eastern bank of the Sado river. A mid-late Famennian age has been assigned based on significant presence of the key miospore species Grandispora cf. cornuta and Rugospora flexuosa, indicating a VCo Miospore Biozone for the Vale de Parreiras Formation. This age is older than previously considered for this formation, even despite the lack of palaeontological information and geochronological age determinations. This new attained palynological age provides helpful informations for the interpretation of regional tectonic structures. Also, its stratigraphic position could be reinterpreted and correlated to other late Famennian age units of Iberian Pyrite Belt, for instance, to the Phyllite-Quartzite Group. The new palynological age indicates that the Vale Parreiras Formation lithologies were deposited and belong to the same palaeogeographic realm as the former group during Late Devonian times. It may also suggest important post Variscan uplift of the Iberian Pyrite Belt in the area east of the Corona-Sado Fault and south of the Grândola Fault. These results also indicate a significant exposure of the mid-late Famennian basement wich can be considered a less favourable scenario to mineral exploration in this Iberian Pyrite Belt sector.
- Idade e ambientes deposicionais da sucessão do Karoo Inferior da Bacia Carbonífera de Moatize em Moçambique: compreenções sobre a história pós-glacial do Gondwana centralPublication . Fernandes, Paulo; Hancox, J.; Mendes, Márcia; Pereira, Zélia; Lopes, Gilda; Marques, João; Jorge, Raul CG Santos; Albardeiro, Luís
- 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).
- The paleoenvironmental and thermal histories of the Permian Irati formation shale in the paraná basin, Brazil: An integrated approach based on mineralogical and organic imprintsPublication . Rocha, Rocha, H.V.; Sant'Anna, L.G.; Rodrigues, Cristina F.A.; Mendes, Márcia; Pereira, Zélia; Lopes, Gilda; Fernandes, Paulo; Pereira, Egberto; Tassinari, Colombo C. G.; Sousa, M.J. Lemos deABSTRACT: Mineralogical assemblages and organofacies are important sources of information to recover the paleoenvironmental and thermal histories of shale deposits. In this study, a detailed qualitative and quantitative characterization of the Permian Irati Formation (Assistência Member) shale is based on mineralogical (XRD and SEM-EDS) and organic components (TOC, Rock-Eval pyrolysis, organofacies, TAI, fluorescence and vitrinite reflectance measurements) and provides integrated data about sediment provenance, depositional environment, diagenesis, and thermal history, while supporting interpretations on the Paraná Basin (PB), Brazil, paleogeography and its correlation to the southwest Gondwana. The results revealed a prevailing type I/II kerogen, with type III kerogen being also present but mainly confined along the paleoshoreline of the PB. The dominance of fluorescent amorphous organic matter (AOM) combined with framboidal pyrite suggests microbial activity in an anoxic-dysoxic neritic-marine paleoenvironment. Additionally, common to abundant well-preserved phytoclasts, as well as the occurrence of Botryococcus braunii, indicates freshwater influx in a brackish marine depositional setting. Immature to early-oil window thermal maturities prevail across the PB, according to the organic maturation indicators. The combined analysis between the organic matter evolution with clay mineralogy, such as the occurrence of interstratified clays (e.g., I/S) and its positive correlation with depth suggest that burial diagenesis reached the transition to early catagenesis on the north, southeast, and south of the basin, attributing a shale oil potential for the Irati Formation on a regional scale. Local scale imprints of the Early Cretaceous Paraná-Etendeka Large Igneous Province (LIP), and its thermal effect in the Irati Formation shale components, are recorded as clay authigenesis (e.g., smectite webby texture and clay coating development), crystallization of minerals by low to high-grade of thermal alteration (e.g., corrensite, talc, lizardite and diopside), and by local scale gas-window maturities. Such thermal alteration, identified in the proximity to intruded sills and dykes, led to a heterogeneous organic maturation pattern with implications on shale gas and shale oil potential of the Irati Formation shale, demonstrating that these subjects in the Paraná Basin should be assessed locally.
- Late Permian palaeoenvironmental evolution of the Matinde Formation in the Muarádzi Sub-basin, Moatize-Minjova Basin, MozambiquePublication . Lopes, Gilda; Pereira, Zélia; Fernandes, Paulo; Mendes, Márcia; Marques, João; Jorge, Raul CG SantosABSTRACT:A multidisciplinary study involving lithofacies analysis, palynofacies, and palynology is presented for the Muaradzi Sub-basin. This sub-basin is part of the Moatize-Minjova Basin (MMB), an important Karoo aged coalfield in Mozambique. A total of 99 core samples from 3 coal exploration boreholes (DW11, DW21, and DW141) were analysed and all the successions were assigned a Lopingian age based on palynology. According to the data, in the Muar ' adzi Sub-basin, a vast lowland fluvial setting existed with floodplains and wetlands, in an area controlled by tectonic movements associated with a continental rifting phase. Typical vegetation of the Glossopteris Province is recorded in the palynological assemblages of this sub-basin, which allowed for the characterization of a flora dominated by glossopterids (Protohaploxypinus and Striatopodocarpites) and gymnosperm pollen (Alisporites). Other palynomorphs revealed the presence of gingkoales, ferns (Filicopsida), sphenopsids, and lycopsids in the area, indicating a typical lowland setting. Humid and warm climates, associated with higher CO2 atmospheric levels, promoted the growth of widespread vegetation that led to the development of the thick coal beds in anoxic to dysoxic depositional environments.
- New pollen taxon Syncolpraedapollis angolensis nov. gen. sp. nov.: A noteworthy discovery reported in the preliminary investigation of the latest Eocene-latest Oligocene deposits in the Kwanza Basin, AngolaPublication . Mendes, Márcia; Pereira, Zélia; Rodrigues, Cristina F.A.; Nsungani, Nsungani, P.C.ABSTRACT: A palynostratigraphic study of the upper Cunga and lower Quifangondo deposits in the Cabo de São Brás section, Kwanza Basin, Angola, has revealed a new pollen named Syncolpraedapollis angolensis nov. gen. sp. nov. This finding was part of a wider survey in the upper Cunga and lower Quifangondo deposits of the Cabo de São Brás section, Kwanza Basin, Angola, covering the latest Eocene to the latest Oligocene. The novel pollen features unique characteristics, notably a 3-syncolporate structure with well-defined and distinctive pores. The pollen grain is adorned with a free but irregular reticulum with an irregular polygonal mesh. Syncolpraedapollis angolensis nov. gen. sp. nov. is sporadically but consistently observed within the latest Eocene-latest Oligocene interval, conspicuously absent in the underlying Eocene sediments (lower Cunga Formation) and occurring infrequently in the latest Oligocene sediments (lower Quifangondo Formation). Thus, it is plausible to infer a limited age range, likely restricted to the latest Eocene-latest Oligocene, as previous studies in the Kwanza Basin have not documented this pollen.
- Palynological Report Alvalade: Sesmarias IIPublication . Pereira, Zélia; Mendes, Márcia
- Relatório palinológico - Corte Via Vai (Formação Almoster) : Rio Maior, PortugalPublication . Mendes, Márcia; Pereira, Zélia