Petrogenesis of the Peneda-Gerês massif

Petrogenesis of the Peneda-Gerês massif: evidences from zircon internal structure and trace element geochemistry

Apresentado na X Semana de Geoquímica e IV Congresso de Geoquímica dos Países de Língua Portuguesa, Braga-Portugal, Março de 1997

Abstract
The Peneda-Gerês massif is a late-Hercynian granitic pluton of subalkaline ferropotassic affinity. Zircon internal structure and trace element geochemistry data from three of its units (the Gerês, Paufito and Illa granites) reveal the existence of two kinds of inherited cores. In the least evolved samples, cores similar to others found in massifs of the same nature testify magma mingling between an alkaline and a calc-alkaline magma. In more evolved samples, and to a greater extent in the Illa granite, a heterogeneous zircon core population with calc-alkaline and anatectic characteristics is found and could only have resulted from contamination, taken place not early in the magmatic history.

References
La Roche H., Stussi J.M., Chauris L. (1980) Les granites à deux micas hercyniens français. Essai de cartographie et de corrélations géochimiques appuyées sur une banque de données. Sci. de la Terre, 24, 1: 5-121.
Mendes A., Dias G. (1996) Petrology and geochemistry of late-Hercynian subalkaline plutonism in the Central Iberian Zone: the Peneda-Gerês granitic massif. C. R. Acad. Sci. Paris, 323, série IIa: 665-672.
Moreira A. (1984) Carta Geológica do Parque Nacional da Peneda-Gerês à escala 1/50 000. Serviços Geológicos de Portugal e Serviço Nacional de Parques, Reservas e Conservação da Natureza.
Nachit H., Razafimahefa N., Stussi J-M., Carron J.P. (1985) Composition chimique des biotites et typologie magmatique des granitoïdes. C.R. Acad. Sci. Paris, 301, série II: 813-818.
Pupin J.P. (1981) A propos des granites potassiques. C.R. Acad. Sc. Paris, 292, série II: 405-408.
Pupin J-P. (1988) Granites as indicators in paleogeodynamics. Rend. Soc. Ital. Mineral. Petrol., 43-2: 237-262.
Pupin J-P. (1992) Les zircons des granites océaniques et continentaux. Bull. Soc. géol. Fr., 163, 4: 495-507.
Pupin J-P. (1994) Caractérisation des protolithes des migmatites et granites anatectiques crustaux d'après l'étude des zircons. C.R. Acad. Sc. Paris, 319, série II: 1191-1197.
Pupin J-P. (1995a) Le zircon, marqueur de mélanges magmatiques à l'origine de granites de l'association subalcaline ferro-potassique: exemple du Mont-Blanc (Alpes). Reún. Spéc. Soc. géol. Fr. & AGSE, Nice, 10.
Pupin J-P. (1995b) Discordant cores in zircons and granite genesis. Hutton Symposium, Maryland, USA.
Pupin J-P., Persoz F. (1995) The origin of high-K subalkaline granites from zircon studies. EUG VIII, 4, Strasbourg.
Tomas J.F., Mateo E.P. (1972a) Mapa geológico de España (Lovios- 301), 1/50 000. Inst. Geol. y Min. España.
Tomas J.F., Mateo E.P. (1972b) Mapa geol. de España (Portela d'Home-336), 1/50 000. Inst. Geol. y Min. España.

Presentations