65 documents found, page 1 of 7
Parental magma signatures recorded in hybrid zones
Rodriguez, Carmen; Marti, Juan; Pereira, M. FranciscoMixing of magmas has been argued as a process to account the intermediate composition of magmatic systems. The coalescence of magmas of contrasted compositions in composite magma chambers is fact observed in fossil magma chambers or plutons and is also deduced from lava sequences in volcanic successions. Nevertheless, it remains unclear if this process can produce magma with an intermediate composition. Hybrid ...
Geodiversidade da região de Évora
Pereira, M. Francisco; Gama, Cristina; Figueira, Francisco; Morais, PedroNo centro histórico da cidade de Évora, são relativamente escassos os afloramentos de rocha bem preservados, o que limita as oportunidades de visitantes e residentes de contactarem diretamente a geodiversidade local. Esta situação torna particularmente relevante a identificação e a valorização de outro tipo de informação geológica acessível na cidade. Assim, o objetivo principal deste guia é inventariar e descr...
Mississippian synorogenic sedimentation in the Variscan belt: Why are NW and SW...
Dias da Silva, Ícaro; Pereira, M. Francisco; Gonzalez Clavijo, EmilioDevonian-Carboniferous synorogenic sedimentation is described across the Variscan orogen, as well-preserved exposures in late orogenic structures between continental blocks. Variscan marine sedimentary sequences are described in both colliding continents: Gondwana representative of the southern subducting super-plate, and Laurussia considered as the overriding block. The Variscan synorogenic basin distribution ...
Variability in the sources of North Gondwana Cadomian basins tracked by Nd isot...
Fuenlabrada, Jose Manuel; Arenas, Ricardo; Pereira, M. Francisco; Rojo Perez, Esther; Sanchez Martinez, Sonia; Diez Fernandez, RubenThe Cadomian Orogeny encompassed the opening and closure of oceanic domains and associated sedimentary basins in the northern margin of Gondwana from Ediacaran to Early Cambrian time. In the Iberian Massif, these Cadomian basins are included in autochthonous and allochthonous (far-travelled) terranes of the Variscan Orogen. A compilation of Nd isotope information of Ediacaran-Lower Cambrian siliciclastic series...
Cadomian arc recycling along the northern Gondwana margin: Source-inherited com...
Pereira, M. Francisco; Gama, Cristina; Dias da Silva, Icaro; Fuenlabrada, Jose Manuel; El Houicha, MohamedRhyolites and rhyolitic tuffs of the Freixo-Segovia ´ Volcanic-Sedimentary Complex of the Cambrian of the OssaMorena Zone (Variscan belt, SW Iberia) were analyzed for petrography, major and trace element geochemistry, Sm–Nd isotopes and U–Pb zircon geochronology in order to deduce magma sources. New U–Pb zircon age data indicate that Freixo-Segovia ´ rhyolitic rocks, previously assigned to the Terreneuvian, for...
Visean high-K mafic–intermediate plutonic rocks of the Ossa–Morena Zone (SW Ibe...
Pereira, M. Francisco; Dias da Silva, Icaro; Rodriguez, Carmen; Corfu, Fernando; Castro, AntonioField relationships and new U–Pb geochronology data indicate a temporal link between the diverse high-K mafic–intermediate magmas of the Ossa–Morena Zone (OMZ). Ages of c. 338–335 Ma for the Vale de Maceiras gabbro and the Campo Maior microdiorite and quartz-diorite indicate that plutonism took place during a Variscan extensional D2 deformation event in the OMZ. The syntectonic nature of the Vale de Maceiras pl...
The influence of synorogenic extension on the crustal architecture of North Gon...
Dias da Silva, Ícaro; Pereira, M. Francisco; Gama, Cristina; Hart, Lourenço S.; Barrios Sanchez, Santos; Alves, Kelvin dos Santos; Gomez Barreiro, JuanA new structural study of a D2–M2 tectono-thermal structure in SW Iberia (Ponte de Sor–Seda gneiss dome) characterized by a spatial distribution of telescoping isograds providing a record of Buchan-type metamorphic conditions is presented. It comprises an infrastructure made up of the lower gneiss unit (LGU) and the intermediate schist unit (ISU), separated by early D2 ductile extensional shear zones. The LGU a...
The granite-hosted Variscan gold deposit from Santo António mine in the Iberian...
Neiva, Ana; Moura, Antonio; Leal Gomes, Carlos; Pereira, M. Francisco; Corfu, FernandoThe study area is located in the Central Iberian Zone, a major tectonic unit of the Iberian Massif (Variscan belt). In this region the basement is composed of Cambrian-Ordovician sedimentary and minor volcanic rocks that underwent deformation and metamorphism during the Carboniferous. These metamorphic rocks host ca. 331–308 Ma granitic plutons emplaced during the D2 extensional and D3–D4 contractional deformat...
Comment on Baltic provenance of top-Famennian siliciclastic material of the nor...
Pereira, M. Francisco; Silva, J. Brandão; Gama, CristinaKoltonik et al. (Int J Earth Sci 107:2645–2669, 2018) evidence that the Late Devonian siliciclastic rocks from the Rheno- Hercynian Zone, in Germany, derived from Baltica and Scandinavian Caledonides. This finding together with what is known about the provenance of the Pulo do Lobo and South Portuguese zones, in Portugal and Spain, reinforces the probability that Late Devonian basins may have been sourced from ...
Evidence formulti-cycle sedimentation and provenance constraints from
Pereira, M. Francisco; Gama, Cristina; Chichorro, Martim; Silva, Jose B.; Gutierrez-Alonso, Gabriel; Hofmann, Mandy; Linnemann, Ulf; Gartner, AndyLaser ablation ICP-MS U–Pb analyses were conducted on detrital zircons of Triassic sandstone and conglomerate from the Lusitanian basin in order to: i) document the age spectra of detrital zircon; ii) compare U–Pb detrital zircon ages with previous published data obtained from Upper Carboniferous, Ordovician, Cambrian and Ediacaran sedimentary rocks of the pre-Mesozoic basement of western Iberia; iii) discuss p...