U–Pb age constraints on the protolith, cooling and exhumation of a Variscan middle crust migmatite complex from the Central Iberian Zone: insights into the Variscan metamorphic evolution and Ediacaran palaeogeographic implications

Abstract

The Figueira de Castelo Rodrigo – Lumbrales Anatectic Complex (FCR-LAC) located in the Central Iberian Zone of the European Variscan Belt is delimited by two shear zones, which have been interpreted as constraining its exhumation. New U-Pb zircon and apatite ages for the migmatites allowed to obtain a peak metamorphic age of the anatectic complex (316.8±2.0 Ma), and to estimate fast cooling (7-54 °C/Ma) and fast exhumation (0.2-1.3 mm.a-1) after a vertical displacement of ca. 6-9 km.Our results show a similar zircon age distribution between migmatites and the Excomungada Formation from the host Ediacaran-Cambrian Douro-Beiras Supergroup (DBSG), but the existence of an inherited zircon population with ca. 500 Ma, absent in the metasedimentary units, suggests the contribution of Ollo de Sapo magmatic rocks during the Lower-Middle Pennsylvanian melting events.Detrital zircon ages of the Pinhão Formation (Douro Group) have contrasting sources to units from the Beiras Group, which may indicate the presence of a barrier that prevented older detrital components from reaching the Douro basin. However, at odds with what has been postulated before, such barrier must have been placed farther south of the FRC-LAC, and thus not coincident with the Juzbado-Penalva do Castelo shear zone.Supplementary material:https://doi.org/10.6084/m9.figshare.c.6002006

Cadomian/Pan-African consolidation of the Iberian Massif assessed by its detrital and inherited zircon populations: is the ~610Ma age peak a persistent Cadomian magmatic inheritance or the key to unravel its Pan-African basement?

“…iv) The relative low proportion of Mesoproterozoic zircons in the OMZ and the WALZ-CZ, suggesting proximity to the West African Craton (WAC). The opening of the system to Stenian-Tonian zircons is only statistically significant in the Early Ordovician (both in Iberia and North Africa) and probably indicates the influence of the Arabian-Nubian shield (ANS) (Altumi et al, 2013;Avigad et al, 2003;Casas and Murphy, 2018;Ferreira et al, 2022;Goodge et al, 2004;Keppie et al, 1998;Lains Amaral et al, 2022;Linnemann et al, 2004;Williams et al, 2012). In the Ediacaran and the Cambrian, the relatively minor subpopulation of these grains may be explained by assuming the long-distance transport of sediments and the high degree of sediment mixing as a means of dilution of the proportion of these ages (Avigad et al, 2003).…”

“…These scarce igneous remnants of the magmatic arc occur in parallel with large volumes of synarc-and back-arc-related sediments (the so-called Série Negra [SN] Formation). The OMZ is bounded to the North by the CIZ, whereas the Douro-Beiras Supergroup features the oldest outcrops, including the Beiras and Douro Groups, which consist of Neoproterozoic-to-early-Cambrian metasedimentary rocks (Ferreira et al, 2022;Medina et al, 1998;Meireles, 2020;Sousa and Sequeira, 1993).…”

“…4B, C) generally indicates the location of the respective sedimentary basins in different Late-Ediacaran paleogeographic scenarios. The prevailing consensus is that the Stenian-Tonian signature indicates proximity to the Arabian-Nubian Shield (ANS) (Altumi et al, 2013;Avigad et al, 2003;Casas and Murphy, 2018;Ferreira et al, 2022;Goodge et al, 2004;Keppie et al, 1998;Lains Amaral et al, 2022;Linnemann et al, 2004;; however, a mechanism producing long-distance sediment dispersion from the ANS or other sources where late Stenian-Tonian phenomena are described as a major event could provide an alternative interpretation (Fig. 8).…”

Petrogenesis and tectonic-magmatic context of emplacement of lepidolite and petalite pegmatites from the Fregeneda-Almendra field (Variscan Central Iberian Zone): clues from Nb-Ta-Sn oxide U-Pb geochronology and mineral geochemistry

“…The pegmatites of the FA field were emplaced within a belt of metasedimentary rocks in contact to the south with a major anatectic dome and bounded by sinistral strike-slip shear zones; the dome mostly consists of syntectonic two-micabearing leucogranites and migmatites, referred to as the Figueira de Castelo Rodriguo-Lumbrales (FCL) complex (Díez Fernández and Pereira, 2016;Ferreira et al, 2019Ferreira et al, , 2020Ferreira et al, , 2022 (Fig. 2a).…”

“…319-311 Ma, zircon U-Pb;Ferreira et al, 2019), as well as U-Pb zircon ages of associated migmatites (ca. 344-315 Ma;Ferreira et al, 2020Ferreira et al, , 2022. Roda-Robles et al (2009, thus, concluded for an absence of genetic connection between leucogranites from the FCL complex and Li-mineralized pegmatites from the FA field, and proposed a genetic link with non-outcropping late-to post-orogenic granites.…”