U–Pb zircon and monazite geochronology of post-collisional Hercynian granitoids from the Central Iberian Zone (Northern Portugal)

Late-Variscan emplacement and genesis of the Vieira do Minho composite pluton, Central Iberian Zone: Constraints from U–Pb zircon geochronology, AMS data and Sr–Nd–O isotope geochemistry

“…These ages are consistent with published zircon U-Pb ages on neighbouring granite plutons from northern Portugal (Dias et al, 2002, and references therein). They furthermore agree with ages, which have been reported from Aguado et al (2005), Dias et al (1998) and Fernández-Suárez et al (2000) for late-D 3 plutonism in the Cental Iberian Zone (306-311 Ma).…”

“…The late deformation phase, D 3 , Namurian-Westphalian in age, is correlated to the post-thickening and extension which marked the end of the collision process (Dias and Ribeiro, 1995;Lagarde et al, 1992). The events related to this tectonic phase were marked by vertical folds with subhorizontal axes and strike-slip sinistral and dextral, subvertical shear zones which controlled the large volume of orogenic granitic rocks emplaced in the Central Iberian Zone, (Aguado et al, 2005;Almeida et al, 2002;Dias et al, 1998Dias et al, , 2002Ferreira et al, 1987;Martins et al, 2009Martins et al, , 2011Noronha et al, 1979). Based on field and geochronological data, these Variscan granites were divided into two main groups (Dias et al, 1998;Ferreira et al, 1987;Martins et al, 2009Martins et al, , 2011: synorogenic (syn-late and late to post-D 3 ; 320-300 Ma) and late to post-orogenic (post-D 3 ; 299-290 Ma).…”

“…The U-Pb isotopic data for the MRG was obtained by Dias et al (1998) yielding an age of 307 ±3.5 Ma (upper intercept). These data led us to consider that the 310 ± 2 Ma and the 307± 3.5 values are likely to be the age of emplacement and crystallisation of the monzogranites.…”

Genesis and emplacement of felsic Variscan plutons within a deep crustal lineation, the Penacova-Régua-Verín fault: An integrated geophysics and geochemical study (NW Iberian Peninsula)

“…However the field relations, late-tectonic emplacement along the same tectonic lineation, led us to suppose that they have similar intrusion ages. The available U-Pb and Rb-Sr ages clearly indicate a post-D 3 emplacement for these granites which agree with the geological data and the AMS studies (Sant'Ovaia, 2000;Sant'Ovaia et al, 2000), as well as to the geochronologic data available for post-D 3 Variscan granitoids in Northern Portugal (Pinto et al, 1987;Dias et al, 1998;Martins et al, 2001;Mendes and Dias, 2004). In terms of Sr and Nd compositions, the VPAG and the AFG present the same rather little evolved isotope composition with ( 87 Sr/ 86 Sr) 299 between 0.7067 to 0.7071 and 0.7076 to 0.7079, respectively, whereas εNd 299 is very similar in both granites around to −2.5 ( Table 2).…”

“…During this post-collisional stage a continuous magmatic activity (mainly granitic) took place in the Central Iberian Zone and consequently in Northern Portugal. Based on several geological data and U-Pb emplacement ages related to this third Variscan phase D 3 Dias et al, 1998;Martins, 1998), the post-collisional granites were divided into the following groups: synorogenic (sin-late-and late to post-D 3 ; 320-300 Ma) and late to post-orogenic (post-D 3 ; 299-290 Ma). The emplacement of the Vila Pouca de Aguiar and the Águas Frias-Chaves granite plutons, located in the Central Iberian Zone, Northern Portugal, (Farias et al, 1987), was controlled by the late brittle deformation phase, post-D 3 (Martins, 1998).…”