PRE-ALPINE MIGMATITIC ROCKS AND ACID TO INTERMEDIATE ORTHOGNEISSES IN PENTELIKON MOUNTAIN (NE ATTICA, GREECE)


I. Baziotis
E. Mposkos
V. Perdikatsis
Résumé

In the broad area of Pentelikon Mountain, which is part of the Attic-Cycladic crystalline belt, metamigmatites and orthogneisses occur as tectonic slices within the calc-schists or between calcschists and marbles. In the metamigmatites relic of migmatitic fabrics, comprising leucosomes and melanosomes, and cross-cutting aplitic and pegmatitic dykes are still preserved. The orthogneisses have dioritic to granitic composition. They are interpreted to be probably formed in a magmatic arc setting. Granitic orthogneisses show high-K contents and are enriched in LILEs and depleted in HFSEs. They also exhibit fractionated REE patterns with slight to strong negative Eu anomaly. The exceptionally high K2O contents (>7%) and the very low Na2Û contents (0.4-0.98 wt%) of certain phengite-orthogneisses with ultramylonitic textures are attributed to metasomatic processes that occurred during ultramylonitization.

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  • Rubrique
  • Petrology
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Références
Altherr R., Holl Α., Hegner E., Langer C. & Kreuzer H. 2000 High-potassium, calc-alkaline l-type plutonism in the European Variscides: northern Vosges (France) and northern Schwarzwald (Germany). Lithos. 50, 51-73
Andriessen P.A.M., Banga G. & Hebeda E.H. 1987 Isotopie ages study of pre-alpine rocks in the basal units of Naxos, Sikinos, los, Greek Cyclades. Geologie Mijnb., 66, 3-14
Baziotis I., Mposkos E. & Perdikatsis V. 2004 Alpine high-pressure/low-temperature metamorphism in Penteli area (NE Attica, Greece). 32th Int.Geol.Con.,Florence.
Ebadi A. & Johannes W. 1991 Beginning of melting and comparison of first melts in the system Qz-Ab-Or-H20-C02. Con.Min.Pet., 106,286-295
Engel, M. & Reischmann, T. 2001 Upper Carboniferous magmatism in the central Aegean region: evidence from basement gneisses of the Cyclades. J. Conf. Abs. 6, 318.
Harris N.B.W., Pearce JA. & Tindle AG. 1986 Geochemical characteristics of collision-zone magmatism. In: Coward M.P. & Ries A.C. (eds.) Collision Tectonics.Geol.Soc.Spec.Publ.19,67-81
Hart S.D. & Reid M.R. 1991 Rb/Cs fractionation: A link between granulite metamorphism and the S-process. Geochimica et Cosmochimica Acta, 55, 2379-2383
Katsikatsos G. 1977 La structure tectonique d Attique et de l'ile d'Eubee. Reun.extr.des.Soc.Geol de France et de Grece, 1976, Bull.Soc.Geol.France, 19, 75-80
Kessel, G. 1990 Untersuchungen zu Deformation und metamorphose im Attischen Kristallin, Griechenland. Berliner Geowissenschaft. Abhandlungen, Reihe A, Band 126, Berlin, 150 S
Lozios S. 1993 Tectonic analysis of the metamorphics of NE Attica (Greece). Ph.D. thesis, University of Athens, 299pp (in Greek with English abstract )
Patino Douce A.E. & Beard J.S. 1995 Dehydration-melting of biotite gneiss and quartz amphibolite from 3 to 15 kbar. J.Petrol., 36, 707-738
Pearce J.A. 1983 Role of the sub-continental lithosphère in magma genesis at active continental margins. In: Hawkesworth C.J. & Norry M.J. (eds.), Continental Basalts and Mantle Xenoliths. Shiva, UK, 230-249
Pearce J.A., Harris N.B.W. & Tindle A.G. 1984 Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. J. Petrol., 25,4, 956-983
Pe-Piper G. 1982 Geochemistry, tectonic setting and metamorphism of mid-Triassic volcanic rocks of Greece. Tectonophysics, 85, 253-272
Singh J. & Johannes W. 1996 Dehydration melting of tonalities: Part II. Compositions of melts and solids. Con.Min.Pet.,125, 26-44
Sun, S.S. & McDonough, W.F. 1989 Chemical and isotopie systematics of oceanic basalts: implications for mantle composition ani processes. In: Saunders A.D. and Norry M.J. (eds.), Magmatism in ocean basins. Geol.Soc.London.Spec.Pub., 42, 313-345
Wijbrans J. R., Schliestedt M. & York D. 1990 Single grain argon laser probe dating of phengites from the blueschist to greenschist transition on Sifnos (Cyclades, Greece). Con.Min.Pet., 104,104, 582-593
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