Percorrer por autor "Linnemann, Ulf"
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- Dados geocronológicos para o soco pré-Mesozoico localizado a Oeste da Falha Porto-Tomar: implicações geodinâmicasPublication . Santos, Telmo M. Bento Dos; Chichorro, Martim; Carvalho, D.; Cachapuz, P.; Solá, A. Rita; Dantas, E.; Romão, José; Moreira, Noel; Silva, I. Dias da; Clavijo, E.; Díez-Montes, Alejandro; Valverde-Vaquero, Pablo; Santos, R. V.; Linnemann, UlfSUMMARY: Geochronological data from the pre-Mesozoic basement of the Lusitanian Basement (West of the Porto-Tomar Fault) was obtained. Results show a predominant Cadomian/Pan-African and Eburnean inheritance/source, placing this sector as a peri-Gondwanan domain. However, two major differences can be seen in the data: samples with a clear absence in Mesoproterozoic ages vs. samples with a clear presence of these ages and Silurian-Devonian ages. If the former show clear signs of affinity with the Ossa-Morena Zone, the latter are similar to the South Portuguese Zone, being one of the samples, probably deposited in the Middle-Upper Devonian, interpreted as having a mixed source.
- Ediacaran and early-palaeozoic bimodal volcanism in the Ossa-Morena Zone, SW Iberian Massif: New clues for intraplate rifting shortly after the Cadomian OrogenyPublication . Cachapuz, P.; Chichorro, Martim Afonso; Bento dos Santos, Telmo; Carvalho, D.; Linnemann, Ulf; Zieger-Hofmann, M.; Zieger, J.; Dantas, E.; Santos, R. V.; Moita, Patrícia; Beltrame, M.; Solá, A. Rita; Díaz-Azpíroz, M.; Fernández, C.ABSTRACT: This study focuses on bimodal meta-volcanic rocks present in the Iberian Massif, in the Evora-Aracena Metamorphic Belt of the Ossa-Morena Zone (OMZ), near the boundary with the South Portuguese Zone. New petrological, geochemical (whole-rock and Sr-Nd isotopes) and LA-ICP-MS U-Pb zircon geochronology data are presented to track the magmatic evolution of both felsic and mafic rocks and their respective geodynamic setting during the transition between the Cadomian Orogeny and subsequent Palaeozoic rifting events. Our research shows that the Evora-Aracena Metamorphic Belt (EAMB) in the southwestern OMZ possesses a significant record of the transition between the Cadomian and Variscan cycles. U-Pb geochronological data confirm the existence of both felsic and mafic Ediacaran igneous rocks (546 and 556 Ma, respectively), a novelty in the region. The Cadomian-related felsic rocks show geochemical similarities to meta-felsic rocks formed during the initial phases of the Cambrian rifting event, namely very negative epsilon Nd values (-10.1 to -11.8), depleted HREE patterns and orogenic signatures. Such similarities imply that meta-felsic rocks formed in the earliest stages of the Cambrian Rift-to-Drift event resulted from a shallower melting. Moreover, meta-felsic rocks formed in the early stages of the Cambrian rifting (525 Ma) present a significant amount of Ediacaran aged zircons, whereas the Cadomian-related counterparts display a few discordant Cambrian ages, likely a consequence of Pb-loss. This indicates that the convergent, subduction-related regime that prevailed during most of the Cryogenian-Ediacaran times along the boundaries of NW Gondwana was swiftly supplanted by a rift-dominated regime during the Cambrian, with no substantial gap between these two thermal events. Meanwhile, meta-felsic rocks formed during the Rift-to-Drift (525-480 Ma) event exhibit progressively higher epsilon Nd values (-5.0 to +3.0), HREE-enrichment, as well as anorogenic signatures, denoting an increasing contribution of mantle-derived melts. This increasing mantle contribution eventually led to the occurrence of bimodal magmatism in the Middle Cambrian Main Rift event. Such Cambrian mafic rocks, unlike the Ediacaran mafic rocks that present flat REE patterns and continental arc signatures, display varying degrees of LREE enrichment and N-MORB to E-MORB signatures.
- Fragmentation of Neoproterozoic magmatic arcs along the northern Gondwana margin in the Late Ediacaran (SW Iberia)Publication . Chichorro, Martim; Solá, A. Rita; Pereira, M. F.; Linnemann, Ulf; Hofmann, Mandy; Silva, J. B.
- Idades U-Pb dos zircões detríticos do Grupo das Beiras - implicações para a evolução do SW da Ibéria durante o NeoproterozóicoPublication . Solá, A. Rita; Chichorro, Martim; Pereira, M. F.; Medina, Jorge; Linnemann, Ulf; Hofmann, Mandy; Silva, J. B.
- Provenance analysis of Lower Palaeozoic siliciclastic rocks of the Southwestern Iberia (Ossa-Morena Zone) : distal shelf deposition on the North Gondwana passive marginPublication . Pereira, M. Francisco; Chichorro, Martim; Lopes, C.; Solá, A. Rita; Silva, J. Brandão; Hofmann, Mandy; Linnemann, Ulf
- Provenance analysis of Lower Paleozoic siliciclastic rocks of SW Iberia (Ossa-Morena Zone) : distal shelf deposition in the North Gondwana passive marginPublication . Pereira, Manuel Francisco Costa; Chichorro, Martim; Lopes, C.; Solá, A. Rita; Silva, J. Brandão; Hofmann, Mandy; Linnemann, Ulf
- Provenance analysis of the Late Ediacaran basins from Southwestern Iberia (Série Negra Succession and Beiras Group) : evidence for a common Neoproterozoic evolutionPublication . Chichorro, Martim; Solá, A. Rita; Pereira, M. Francisco; Hofmann, Mandy; Linnemann, Ulf; Gerdes, Axel; Medina, Jorge; Lopes, L.; Silva, J. Brandão
- Provenance analysis of the Late Ediacaran basins from SW Iberia, Serie Negra Succession and Beiras Group : evidence for a common Neoproterozoic evolutionPublication . Chichorro, Martim; Solá, A. Rita; Pereira, Manuel Francisco Costa; Hofmann, Mandy; Linnemann, Ulf; Gerdes, Axel; Medina, Jorge; Lopes, L.; Silva, J. Brandão
- Provenance of Cambrian-Ordovician siliciclastic rocks of the Southwestern Iberia : insights to the evolution of the North Gondwana marginPublication . Solá, A. Rita; Chichorro, Martim; Pereira, M. Francisco; Hofmann, Mandy; Linnemann, Ulf; Gerdes, Axel; Medina, Jorge; Lopes, L.; Silva, J. Brandão
- Provenance of Cambro-Ordovician siliciclastic rocks of the SW Iberia : insights to the evolution of North Gondwana marginPublication . Solá, A. Rita; Chichorro, Martim; Pereira, Manuel Francisco Costa; Hofmann, Mandy; Linnemann, Ulf; Gerdes, Axel; Medina, Jorge; Lopes, L.; Silva, J. Brandão