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- Late Strunian age : a key time frame for VMS deposit exploration in the Iberian Pyrite BeltPublication . Matos, João Xavier; Pereira, Zélia; Rosa, Carlos J. P.; Rosa, Diogo; Oliveira, José Tomás; Relvas, Jorge M.R.S.Estimate of geological environments favorable for the formation of massive sulphide deposits is an important goal to the exploration companies working in the Iberian Pyrite Belt (IPB), the main European VMS base metals province, with giant deposits such as Neves Corvo, Aljustrel (Portugal), Rio Tinto and Tharsis (Spain). Palynostratigraphic research programs using more than 40 exploration boreholes (>30 km length) allowed the dating of the sediments of the Volcano-Sedimentary Complex (upper Devonian to upper Viséan), that host the massive sulphide deposits. Research is based on detailed palynomorphs study. Careful work was focused on dark grey and black shale units that host stockwork and massive ore mineralizations. Felsic volcanic U/Pb age data was also used to confirm the sediment age.Late Strunian (miospore biozone LN, 360.7 ± 0.7 Ma -362 Ma) sediments host the massive sulphide ore at Neves Corvo, Lousal, Caveira and Montinho, mines located in the Portuguese IPB sector. In Spain similar data was obtained at Aznalcollar and Tharsis. The agedata show a favourable geological period of ~2 Ma were paleogeographic conditions were extremely favorable to hydrothermal fluid circulation and VMS deposits formation. Late Strunian age therefore becomes one key exploration guide in IPB.
- A Rota da Pirite, uma rede de sítios geológicos e mineiros dedicada ao património e história da Faixa Piritosa IbéricaPublication . Matos, João Xavier; Pereira, Zélia; Oliveira, José TomásA Faixa Piritosa Ibérica é uma região mineira europeia marcada pela exploração de jazigos de pirite, de óxidos de Mn e Fe e de filões de Cu, Sb, Pb e Ba. Esta actividade extractiva largamente desenvolvida desde a Era romana reflecte-se num valioso património mineiro e geológico. A Rota da Pirite, integrada no projecto Ibero-americano RUMYS, é representada em Portugal pelas minas de São Domingos, Aljustrel, Lousal, Caveira e Cova dos Mouros, assumindo-se como um novo cluster de turismo cultura do Alentejo, localmente apoiado por vários núcleos museológicos e painéis de percurso.
- Late-stage gold (Electrum) in the Lousal Mine, Iberian Pyrite Belt, PortugalPublication . de Oliveira, Daniel Pipa Soares; Rosa, Carlos J. P.; Guimarães, Fernanda; Matos, João Xavier; Rosa, Diogo; Pereira, Zélia; Frias, Vasco C. S.
- Early and Middle Jurassic palynostratigraphy of the Lusitanian Basin in the proto-Atlantic contextPublication . Correia, Vânia; Pereira, Zélia; Riding, James; Duarte, L. V.; Henriques, Maria Helena; Fernandes, PauloSUMMARY: A palinologia é uma ferramenta muito útil nos trabalhos de bioestratigrafia e interpretações paleoambientais, e que pode ser aplicada no conhecimento da geologia da Bacia Lusitânica. Assim, foi desenvolvido um estudo palinoestratigráfico de alta-resolução em 8 cortes do Jurássico Inferior e Médio (Sinemuriano superior—base do Batoniano) da Bacia Lusitânica e, neste trabalho, são apresentados os intervalos de ocorrência e bioeventos associados aos principais taxa identificados, nomeadamente no grupo dos quistos de dinoflagelados.
- New data on the late Famennian miospore assemblage of the Cercal Anticline, westernmost Iberian Pyrite Belt area, PortugalPublication . Pereira, Zélia; Matos, João Xavier; Fernandes, Paulo; Oliveira, José TomásThe Cercal Anticline (CA) is located in the westernmost region of the Iberian Pyrite Belt (IPB). The exposed stratigraphic sequence includes, in ascending order, the Volcano-Sedimentary Complex (VSC) followed by the Xistos das Abertas Fm, which passes gradually to the flysch sequence of the Mira Formation (Carvalho, 1976). The VSC is composed from base to top by: Felsic Volcanics (Vα), that comprehends lavas, pumice and volcaniclastic beccias with intercalations of volcanogenic shales; diabases and intermediate/basic subvolcanics (Vβ); jaspers and the S. Luís Formation (SL), a unit composed of shales, phyllites, siliceous shales and volcanogenic sediments. About 500m NW of São Luís village, at the base of this last unit, brachiopods ascribed to the late Strunian were found (Quiring, 1936). This determination led Carvalho (1976) to assume that the volcanics of the VSC are older than the Strunian, meaning so that this volcanism is the oldest in the Portuguese IPB. The stratigraphic succession of the CA is still poorly constrained, in terms of lithostratigraphy and age. In fact, three boreholes carried out in the hinge zone of the anticline by the Elf Aquitane company, about 1km NW of São Luis village, showed that below the felsic volcanics a thick (>250m) succession of dark shales and siltstones occur. These shales yielded very well preserved specimens of Grandispora echinata together with Ancyrospora spp., Apiculiretusispora sp., Auroraspora macra, Cristicavatispora dispersa, Diducites poljessicus, D. mucronatus, D. versabilis, Emphanisporites annulatus, Grandispora cornuta, Punctatisporites spp., Retispora cf. macroreticulata, Retusotriletes phillipsii, R. planus, R. triangulatus, R. rugulatus, Rugospora explicata and R. radiata. This assemblage indicates the VH Biozone of late Famennian age. It is similar to those found in shales interbedded in felsic volcanics in several regions of the Portuguese Pyrite Belt (Neves Corvo Mine, Albernoa Anticline, São Domingos Mine). Palynostratigraphic research in the CA is currently still in progress. However, these preliminary results show that the age of the CA felsic volcanics is similar to that obtained in the northeastern branches of the Portuguese Pyrite Belt and no prove that the volcanism migrated in time to the NW, as suggested by Carvalho (1976), could be detected.
- Homenagem a José Tomás Oliveira : o Homem e a GeologiaPublication . Pereira, Zélia
- Palynological assemblages from Hongguleleng Formation of Western Junggar, Northwest China and their correlation with conodont zonationPublication . Shen, Zhen; Steemans, Philippe; Pereira, Zélia; Zong, Rui-Wen; Zhang, Xin-Song; Ma, Kun-Yuan; Gong, Yi-MingABSTRACT: The Upper Devonian Hongguleleng Formation is a significant stratigraphic unit near the Frasnian/Famennian and Devonian/Carboniferous boundaries of the Kazakhstan Paleoplate. However, its age is still under debate. A new palynostratigraphic analysis was conducted at the Gennaren section to provide a more accurate biostratigraphic assignment. In this study, we identified 43 species belonging to 26 spore genera, including those in open nomenclature. Despite the poor preservation of the palynofloras, the spore taxa were categorized into two assemblages. Assemblage I is established at the lower part of the lower member of the Hongguleleng Formation, containing Cornispora varicornata, cf. Auroraspora pseudocrista, and Cyrtospora cristifera. Assemblage II is from the upper part of the lower member of the Hongguleleng Formation, including Grandispora cornuta, Grandispora famennensis var. famennensis, Grandispora cf. famennensis var. minutus, Grandispora microseta, and Rugospora radiata. These assemblages are compared with the Western European DV Oppel Zone (lower-middle Famennian), and the GF to VCo Oppel zones. The assemblages are equivalent to the conodont crepida–rhomboidea and marginifera to Lower trachytera zones (middle-upper Famennian).
- 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.