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The Paleoproterozoic orogenies are among the most significant crustal growth events recorded in Western Gondwana, as depicted by their strong detrital zircon signature into the Gondwanan and peri-Gondwanan sediments. Indeed, the Neoproterozoic–Cambrian sediments of peri-Gondwanan terranes, particularly those in Iberia, Meguma, Avalonia, and Ganderia, display distinctive 2.2–1.8 Ga zircon distributions. In the Iberian Massif, the Galicia-Trás-os-Montes (upper allochthonous) and Ossa-Morena zones present distinctive 1.95–1.9 and 2.1–2.05 Ga peaks, whereas West Asturian-Leonese and Cantabrian zones show a prominent ~2.0 Ga peak. The Centro-Iberian Zone also has a curve centred at 2.0 Ga but of greater wavelength. In contrast, the Avalonian and Ganderia sediments show multiple peaks between ~1.6 and ~2.1 Ga, whereas Meguma has a distinctive ~2.05 Ga peak. These unique distributions are most likely paleogeographic indicators of the diachronic Paleoproterozoic orogenic events from the western blocks (Amazonian Craton) to the eastern blocks (Sahara Metacraton) of Gondwana. Indeed, in the Amazonian and the North African Precambrian regions, the magmatic-metamorphic Paleoproterozoic events are mainly constrained to: (1) ~2.0–1.6 Ga in the western Amazonian provinces, (2) ~2.2–2.0 Ga in the Transamazonian province, (3) ~2.2–2.0 Ga in the West African Craton, (4) ~2.1–1.9 Ga in the Trans-Sahara Belt, and (5) ~2.0 Ga in the Sahara Metacraton. Furthermore, North African sedimentary rocks show peaks within 2.1–2.05 Ga in the western block, while eastern blocks show peaks within 2.1–1.9 Ga, which are generally congruent with adjacent cratonic orogenic events. Indeed: (1) Anti-Atlas Tonian-middle Cambrian sedimentary rocks show prominent 2.1–2.05 Ga peaks, coincident with the 2.1–2.05 Ga event in West African Craton, (2) Trans-Sahara Belt Ordovician sedimentary rocks display ~1.75, ~1.9 and ~2.1 Ga peaks congruent with the ~1.9 Ga event present in the basement inlier of this belt, and (3) Sahara Metacraton Tonian sedimentary rocks present a ~2.0 Ga peak consistent with the main 2.0 Ga event in this metacraton. However, Sahara Metacraton Cambrian rocks show 1.85 and 2.05 Ga peaks, most likely suggesting provenance from Trans-Sahara Belt or that these orogenic events have not yet been adequately identified in this metacraton. The 2.2–1.8 Ga zircon distribution is, in some cases, a distinctive feature throughout the Palaeozoic. For example, the middle-upper Devonian sediments of the Iberian Pyrite Belt display a prominent ~2.1 Ga peak, similar to the West African Craton, Anti-Atlas and Meguma, which do not occur in any of the other Iberian zones

Publisher Copyright: © M. Chichorro, A.R. Solá, T.M. Bento dos Santos, J. Lains Amaral, L. Crispim, 2022. This work assessed the age distribution of Cadomian/Pan-African orogenic events (550-590 and 605-790Ma, respectively) in several zones of Iberian Massif by means of detrital and inherited zircon analysis compilation. Detrital zircon age spectra show that throughout the late Neoproterozoic-to-Early Ordovician era (~120Ma sedimentary record), the main systematic peak occurs at ~610Ma, followed by peaks at typical Cadomian ages (~590-550Ma). Inherited zircons incorporated in Cambrian-to-Lower Ordovician igneous rocks show typical Cadomian ages (~590-550Ma) but, once again, a remarkably consistent Pan-African ~610Ma peak occurs. In accordance with compiled zircon data and taking into account the evidence of North African peri-cratonic inliers, Ediacaran (~610Ma) zircons incorporated in Paleozoic magmas provide indirect evidence of Pan-African magmatism, suggesting that these magmas and synorogenic sediments are likely to constitute the cryptic stratigraphic infrastructure of most of the Iberian Massif. The main source of ~610Ma inherited zircons may be the lateral chrono-equivalents of the Saghro and Bou Salda-M`Gouna Groups (Anti-Atlas, Morocco) and/or coeval igneous rocks from West African Craton or Trans-Sahara Belt, emplaced at a stratigraphic level below the late-Ediacaran sediments of the Ossa Morena Zone and the Central Iberian Zone. Assuming that the Iberian crust is a fragment of the Pan-African orogen, a relative paleoposition situated between the West African Craton and the Trans-Saharan Belt during the Late Neoproterozoic is proposed. The closed-system behaviour of Stenian-Tonian detrital zircon ages in the Trans-Sahara Belt suggests that this mega-cordillera acted as a barrier, in paleogeographic terms, to separating the Sahara Metacraton from Iberia. In Iberia, the opening of the system to Stenian-Tonian detrital zircon during the Ordovician indicates that, at that time, the Trans-Saharan Belt had already become a vast peneplain, which favoured a large drainage system with a long-distance transport mechanism that fed the passive continental margins. publishersversion published

AIMS OF THE MEETING: The scientific sessions will be focused on the Pan-African and Cadomian Orogenies recorded in North Africa and western Europe across the Ediacaran Cambrian transition and its bearing in the assembly and demise of Pannotia. Contributions dealing with structural, magmatic, provenance sources, palaeomagnetic, sedimentary, chronostratigraphic and radiometric constraints are particularly welcome. ORGANIZING COMMITTEE: J. Javier Álvaro, Instituto de Geociencias (CSIC-UCM), Spain Martim Chichorro, Universidade Nova de Lisboa, Portugal Gabriel Gutiérrez-Alonso, Universidad de Salamanca, Spain. ABSTRACT: Both the Pan-African orogenic cycle and the peri-Gondwanan Cadomian Orogeny took part in the global tectonic event that led to the rearrangement of Gondwana's west-northern block. An approach to determine the nature of Cadomian - Pan-African events using detrital zircons population from Neoproterozoic-Lower Paleozoic (rift-to-drift cycle) stratigraphic record in Iberian Massif is here discussed. info:eu-repo/semantics/publishedVersion

This is a contribution to the research project PetroGeo (LNEG) A geochronological study using SHRIMP U-Pb analysis of zircon grains has been conducted to date felsic volcanic rocks hosting the six massive sulphide deposits of the giant Aljustrel mining district in the Iberian Pyrite Belt. A multiple method age calculation approach was used to validate and ponder calculated Concordia ages (emplacement and inherited), which included weighted average, probability density peak(s), Tuff Zirc and Unmix functions. This approach was particularly useful to interpret the wide continuous single U-Pb ages (320–405 Ma) recorded in the Aljustrel volcanic rocks. The volcanic pile (>250 m) that hosts the Aljustrel deposits was emplaced between 359 and 353 Ma. Upper Devonian inheritance, representing subvolcanic activity, is well-represented in the volcanic rocks of Aljustrel (373–365 Ma). Older Devonian inherited zircon ages at 405 Ma, 388 Ma and 380 Ma were retrieved, hypothetically representing deep plutonism or other melting episodes, which suggests a long-lasting (~50 Ma) magmatic activity in the Aljustrel district. Older pre-Devonian inherited ages, uppermost Silurian and early to late Cambrian, and post-emplacement ages (~330–345 Ma) were also detected, with the latter reflecting Pb loss most likely driven by the main Variscan orogenic event. Maximum ages obtained for the volcanic rocks in the different deposits open the possibility that the last pulses of volcanic activity and subsequent deposition of the massive sulphides were diachronic in the different Aljustrel sub-basins. Additionally, results imply that, contrary to previously assumed, Gavião and São João-Moinho deposits are probably not the same ore lens disrupted by tardi-Variscan faults. This opens new opportunities for mining exploration and targeting in the Aljustrel district and points out the importance of high-resolution geochronological studies in mining and brownfield areas. info:eu-repo/semantics/publishedVersion

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 discrepancy concerning the age distribution of the felsic volcanic rocks (ca. 356-330 for Pomarão and ca. 365-346 Ma for all NC area) while sediments range from mid-Famennian to late Visean age (VH to NM Miospore Biozone for NC). iii); the Baixo Alentejo Flysch Group (late Visean NM Miospore Biozone onwards in NC), covering the previous sequences and being slightly older than the uppermost volcanic rocks of Pomarão. The correlation between these two structures is supported by geology and isotopic/biozone ages and favours exploration scenarios in both regions. RESUMO: Neste trabalho é discutida a correlação estratigráfica de duas estruturas antiforma marcantes da Faixa Piritosa Ibérica (FPI). Por um lado, a região mineira de Neves-Corvo (NC), a maior mina de sulfuretos maciços vulcanogénicos da Europa, intensamente estudada e, por outro, o setor ocidental da estrutura Pomarão-Puebla de Guzmán-Tharsis, uma das mais importantes e completas secções geológicas cartografadas na província. A sequência estratigráfica completa da FPI está representada nos dois setores, nomeadamente, o Grupo Filito-Quartzítico (PQ), seguindo-se o Complexo Vulcano-Sedimentar (CVS) e o Grupo do Flysch do Baixo Alentejo. À escala local, existe maior variabilidade em termos de fácies litológicas, características petrográficas e de idade. O PQ apresenta base de idade desconhecida, sendo compreendido entre o Givetiano médio (Biozona TA) e o Famenniano superior (Biozona LN, Estruniano). O topo é marcado pela presença de níveis de calcários nos dois locais, com idades aproximadas. No CVS observa-se maior variabilidade de idades, nomeadamente ca. 356-330 Ma no Pomarão e ca. 365-346 Ma para toda a área de NC. Na sua base, predominam essencialmente as fácies de xistos negros (Biozonas de Esporos VH a LN), rochas vulcânicas félsicas interdigitadas e sulfuretos maciços, no caso de NC. A sequência sobrejacente do CVS, inclui unidades de xistos siliciosos com nódulos de diferente composição (Biozona de Esporos NM, Viseano médio) e rochas vulcânicas e vulcanogénicas com um espectro de idades com alguma heterogeneidade. Entre este setor e a secção superior do Complexo existe um nível guia, à escala da província, representado por Xistos Borra de Vinho, também presente nas duas áreas de estudo. Acima deste nível ocorrem sedimentos vulcanogénicos e siliciosos de idade Viseano sup. (Biozona de Esporos NM assinalada em NC) e ca. 330 Ma (em níveis vulcânicos no Pomarão). No topo da sequência, há uma transição das unidades do CVS para os turbiditos da Fm. de Mértola (Viseano sup., Biozona de Esporos NM). Salienta-se o facto das idades da base desta formação flysch serem em NC um pouco mais antigas que o topo do CVS no Pomarão. Deste estudo, enfatiza-se uma maior homogeneidade ao nível das formações sedimentares entre as sequências das duas regiões, comparativamente com as intercalações de origem vulcânica, com carácter mais local e maior variabilidade de fácies. A correlação entre as duas estruturas permite identificar cenários favoráveis à prospeção mineral. info:eu-repo/semantics/publishedVersion

Ordovician geodynamics: The Sardic Phase in the Pyrenees, Mouthoumet and Montagne Noire massifs International Meeting (2017. Figueras, España), This study discusses the differences in detrital zircon populations of the Lower Ordovician Armorican quartzite. In the Iberian Massif, this proximal deltaic to shallow-water nearshore depositional facies (Gutiérrez-Marco et al., 2002) occur widespread in the Cantabrian (CZ,) West Asturian-Leonese (WALZ) and Central Iberian (CIZ) zones. The Armorican quartzite represents a passive margin sequence of the Gondwana margin facing the Rheic Ocean, related to transgression and strong subsidence. At this time, in the OMZ, the equivalent sedimentary units from Lower-Upper Ordovician are represented by more distal shales (Barrancos Formation)., Unidade de Geologia, Hidrogeologia e Geologia Costeira, Laboratório Nacional de Energia e Geologia, Portugal, GeoBioTec, Departamento de Ciências da Terra, Universidade Nova de Lisboa, Portugal, Instituto de Geociencias, Consejo Superior de Investigaciones Científicas, España, Instituto de Geociencias, Universidad Complutense de Madrid, España, Instituto Geológico y Minero de España, España

Ordovician geodynamics: The Sardic Phase in the Pyrenees, Mouthoumet and Montagne Noire massifs International Meeting (2017. Figueras, España), The Early Palaeozoic rift-related igneous activity recorded in the Iberian Massif is subdivisable into three main events separated by relatively quiescent episodes. The so-called Early, Main and late events represent space-temporal diachronic pulses characterized by a progressive variation in the nature of the rift-related magmatism. The first two, Early and Main rift-magmatic events, were defined in detail by Sánchez García et al. (2003) and are almost exclusive of the Ossa-Morena Zone (OMZ), while the late magmatic event mainly occurs in the Central Iberian (CIZ) and Galiza-Trás-os-Montes (GTMZ) zones (Ollo de Sapo Formation and associated plutons)., GeoBioTec, Departamento de Ciências da Terra, Universidade Nova de Lisboa, Portugal, Laboratório Nacional de Energia e Geologia, Portugal, Instituto Geológico y Minero de España, España, Instituto de Geociencias, Universidad Complutense de Madrid, España, Instituto de Geociencias, Consejo Superior de Investigaciones Científicas, España

Ordovician geodynamics: The Sardic Phase in the Pyrenees, Mouthoumet and Montagne Noire massifs International Meeting (2017. Figueras, España), The purpose of this study is to compare the features of the Terreneuvian-Cambrian Series 3 siliciclastic rocks representative of rift stages in the Ossa-Morena (OMZ), Central Iberian (CIZ), West-Asturian Leonese (WALZ) and Cantabrian (CZ) zones of the Iberian Massif (the three latter representing the so-called Cantabro-Iberian Basin), based on zircon age distributions, GeoBioTec, Departamento de Ciências da Terra, Universidade Nova de Lisboa, Portugal, Laboratório Nacional de Energia e Geologia, Portugal, Instituto de Geociencias, Consejo Superior de Investigaciones Científicas, España, Instituto de Geociencias, Universidad Complutense de Madrid, España, Instituto Geológico y Minero de España, España

Ordovician geodynamics: The Sardic Phase in the Pyrenees, Mouthoumet and Montagne Noire massifs International Meeting (2017. Figueras, España), In the Iberian Massif a voluminous igneous activity was recorded along its reputed rifting axial (i.e., the Ossa-Morena Zone, OMZ) where three phases, separated by relatively quiescent periods, are distinguished. The first two, Early and Main rift-stage magmatic events, were defined in detail by Sánchez García et al. (2003) and are almost exclusive of the OMZ, while the Late rift-stage magmatic event mainly occurs in the Central Iberian (CIZ) and Galicia-Trás-os Montes (GTMZ) zones (Ollo de Sapo Formation and associated plutons)., GeoBioTec, Departamento de Ciências da Terra, Universidade Nova de Lisboa, Portugal, Laboratório Nacional de Energia e Geologia, Portugal, Instituto Geológico y Minero de España, España, Instituto de Geociencias, Consejo Superior de Investigaciones Científicas, España, Instituto de Geociencias, Universidad Complutense de Madrid, España

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VII Hutton Symposium on Granites and Related Rocks, Avila, Spain, July 4-9, 2011

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