The Pedregal granite (Portugal): petrographic and geochemical characterization of a peculiar granitoid

• Tipo: Artigo em Revista Científica Internacional
• Data: 2014

Autores

Ferreira, JA (Autor) Outra; Ribeiro, MA (Autor) FCUP; Martins, HCB (Autor) FCUP

Revista

Título: ESTUDIOS GEOLOGICOS-MADRID

Vol. 70

Página Final: e019

ISSN: 0367-0449

Indexação

ISI Web of Knowledge - 4 Citações

Scopus - 6 Citações

Classificação Científica

FOS: Ciências exactas e naturais > Ciências da terra e ciências do ambiente

Outras Informações

ID Authenticus: P-00A-2Y9

DOI: 10.3989/egeol.41730.321

Abstract (EN): The Pedregal granite outcrops in the Central Iberian Zone, northern Portugal, in the eastern border of a synorogenic variscan granite-migmatite complex sub-concordant with the regional metamorphic structures. It is a granitoid (ca. 3 km(2)) with an elongated NW-SE shape intruded in staurolite-micaschist and banded gneiss-migmatite rocks, with local igneous breccias in the contact. The country rocks belong to a metapelitic and metasammitic sequence of Edicarian-Cambrian age, known as the "Complexo Xisto-Grauvaquico" (CXG) which shows a main regional foliation with a NW-SE to NNW-SSE direction. The Pedregal granite is peraluminous (its A/CNK parameter ranges from 1.18 to 1.62), with a magnesian and alkali to alkali-calcic signature. The peculiar features of the granite are high contents of Zr (389 to 435 ppm) and a LREE flat pattern, which are uncommon characteristics for granitic rocks, as well as the corroded shape of the biotite, and the large amount of secondary muscovite. These peculiar features distinguish it from the adjacent synorogenic granites. The field, petrographical and chemical features of the Pedregal granite are in accordance with a second phase of partial melting of a residuum, depleted by melt segregation during a first melting episode with the involvement of peritectic garnet and abundant residual biotite with LREE- and Zr-bearing accessory minerals. Besides, the intrusive character of the granite, and the presence of metasedimentary xenoliths point out to a secondary diatexite.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 9