Las dioritas de Palamós (Cadenas Costeras Catalanas): emplazamiento y cristalización

Abstract

This paper is a case study of one of the mafic-felsic associations of the Hercynian calc-alkaline Catalonian Coastal Ranges B ath olith (NE Spain). Orig in, emplacement and cristaUization paths o f magmas are the aim of the paper. Palamos outcrop shows a quartz-diorite included mainly as enclaves of different shapes and compositions in a feldspar megacrystic biotite-granodiorite host. Multistage magma mingling between two different contrasted magmas seems to be the only way to explain the special features. Relationships between these rocks suggest that they have coexisted in a magmatic state. Two main stages have been recognized through petrological and geochemical studies: own evolution before mixing and interaction and emplacement of both magmas. Thermal equilibrium between them and magmatic movements allows crystal and chemical exchanges in different ways and proportions as crystallization goes on. The effects are acidification of basic magma and basification of the acid one. This process seems to affect only the peripheral part of both intrusions