Large-Scale Hydrothermal Processes in the Hercynian Massives of Eastern Pyrenees (France)

Abstract

Metasomatic processes, resulting in massive feldspar rocks (either albite, oligoclase or K-feldspar) or muscovite+biotite rocks, have affected several palaeozoic massives in Eastern Pyrrnres, including mainly: (1) the Agly massif, composed of metasedimentary (granulite facies) precambrian gneisses overlain by mesoand epizonal schists of ordovician to silurian age; hercynian granodiorites are intrusive in these formations (2) the Millas massif, situated south of the Agly massif from which it is separated by the North-Pyrenean fault, and composed of hercynian granodiorite intruding a series of metapelites, partly preserved as schlieren in the southermost part of the massive. All granitoids exhibit at some places numerous dioritic to gabbroic enclaves, up to several hundred meters large.