Geochronology and isotope geochemistry of granitoids and metasediments of são pedro das Águias area (Tabuaço w project) [Geocronologia e geoquímica isotópica de granitoides e metassedimentos da área de são pedro das Águias (Concessão para a prospeção de w de tabuaço)]
Cerejo T.,University of Aveiro |
Santos J.F.,University of Aveiro |
Sousa J.C.,Rua Centro Empresarial |
Castanho N.,Rua Centro Empresarial |
And 2 more authors.
Comunicacoes Geologicas | Year: 2014
In the area of Quinta de São Pedro das Águias, the following lithologies were identified: biotite-zone “normal” and black phyllites, marbles, calcsilicate (s.s.) rocks and skarns, belonging to the Bateiras Formation, of the Douro Group of the CXG; Paredes da Beira-Tabuaço granite; several aplitic and pegmatitic bodies. Rb-Sr isotope analyses provided a 311±7 Ma whole-rock isochron (MSWD=1.7; initial 87Sr/86Sr = 0,7146) for the granitoids. This date is interpreted here as the emplacement age of the granitoid magmas, during a late stage of the Variscan D3. The granite revealed a S-type nature, namely because it is a muscovite granite, it shows a peraluminous composition (average A/CNK = 1.28), and the Sr and Nd isotope fingerprints (-8.9≤εNd311≤- 7.8; +129≤εSr311≤+192) fit into the composition of metasedimentary crust. The isotope signatures, at 311 Ma, of the granite and of the studied metapelites overlap each other, suggesting that the parental magma was generated by anatexis of Grupo do Douro metasediments. Isotopically, especially due to their lower εNd311, the studied metapelites are clearly distinct from the Grupo das Beiras metasediments (the other major division of the CXG), and, instead, they resemble other metasedimentary units of the Iberian Massif. © 2014 LNEG – Laboratório Nacional de Geologia e Energia IP.