Oliveira, A.J.T., Martins, H.C.B., da Silva, H.M.S.M., 2021. Petrogenetic constraints on the felsic vein magmatism in northern Portugal based on petrological and geochemical data. Comptes Rendus Géoscience – Sciences de la Planète, 353 (1), pp. 377-398″. https://doi.org/10.5802/crgeos.100
Three of the largest granite porphyries of northern Portugal were studied to improve current knowledge on the regional felsic vein hypabyssal magmatism. All porphyries exhibit microcrystalline groundmasses of variable granularity (composed of quartz, K-feldspar, and muscovite), quartz, K-feldspar, plagioclase, biotite, and cordierite phenocrysts, antirapakivi and rapakivi feldspars, embayments in quartz, and enrichments in rare metal incompatible elements. The veins were emplaced along fractures generated during the last phase of the Variscan orogeny. Textural features were presumably conditioned by fast cooling, volatile loss, subsolidus annealing, and the magnitude of thermal contrasts at the time of emplacement. All veins were altered by subsolidus hydrothermal fluids, as suggested by several petrographic and geochemical evidence. The generation of mantled feldspars is probably related to isothermal decompression andmagma mixing, which is compatible with the εNdi signatures (-3.76 to -4.40). Based on this research, both processes have contributed to the petrogenesis of the studied porphyries.
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