Authors: BERNARD PLATEOVET, JEAN BEBIEN, EDILENE GOMES
Abstract: Three acid-basic associations taken in various geodynamical settings are studied: the gabbro-granite association of Porto (Corsica), the associations of the Guevgueli (Greek Macedonia), and the associations of the Piracaia complex (Brazil). The diversity of field relations, the degree of mingling, the origins of the melts are debated for each association, using petrological and geochemical tools for each acid-basic association. An origin by hybridization is assumed for the intermediate rocks of the Porto association, it is tested by numerical calculation. Then, we focus on the mixing process between the comagmatic components. Mixing of melts may have happened by thorough mingling and chemical diffusion under disequilibrium conditions attested by textural characters of the hybrid rocks. The mixing between the contrasted melts can not be complete, it appears that the mean effective ratio between the two mixed components (the effective mixing ratio) in the hybrids is weak compared with the acting volume of mafic magma during the magmatic brecciation, it may be the result of the difference between thermal and chemical rates.
Full Text: PDF