The Vrondou intrusive complex is an Oligocene composite pluton, located close to the Greek-Bulgarian border, north of Serres in Central Macedonia, North Greece, which intrudes marbles and schists of the Lower Tectonic Unit of the Western Rhodope Massif. Vrondou magmas were emplaced at 7.5 to 11 .2 Km depth in distinct «batches» in an extensional tectonic regime. Mafic microgranular enclaves with ellipsoidal or irregular shapes, up to 30 cm in diameter, are present only in the north-eastern part of the pluton. In the south-eastern part of the pluton a small elongated gabbro-dioritic body outcrops. The Vrondou rocks range from gabbro to quartz monzonite having as main ferromagnesian minerals hornblende, biotite and clinopyroxene in various amounts. The rocks as a whole cover a large compositional field, ranging from calc-alkaline to shoshonitic with some rocks falling in the field of potassic series. Two groups of enclaves are evident, one above the shoshonitic boundary and one mainly on the calc-alkaline field. On the basis of petrographic and geochemical data the rock-types fall mainly in five groups, having different genetic and evolutionary paths. Gabbro-dioritic rocks of calc-alkaline affinity evolve through cumulus processes at low pressure in a magma chamber. Monzonitic rocks bearing high-K magmatic enclaves have a shoshonitic affinity and evolve through mixing plus fractional crystallization processes between metaluminous granodioritic-monzogranitic anatectic magmas and mantle derived magmas of lamprophyric affinity. Quartz-monzonitic rocks bearing low-K magmatic enclaves straddle the fields of calc-alkaline and high-K calc-alkaline, and evolve through processes of mixing plus fractional crystallization between anatectic magmas, similar to that of monzonite, and mantle-derived magmas of calc-alkaline affi ìnity. Quartz syenite and granite outcropping in the south-western part evolve through various stages of fractional crystallization with different crystallizing assemblages. The parental magmas for the strongly potassic suite were derived by partial melting of an enriched mantle wedge under different conditions of pressure and/or composition, whereas the parental magmas of the calc-alkaline suite were derived from a less enriched mantle wedge under lower pressure. Intrusions of those mantle derived melts underplate the crust, and supply heat to induce the crustal partial melting that produces metaluminous granodioritic-monzogranitic melts.
Petrology and evolution of transitional alkaline-subalkaline granitoids from Vrondou (NE Greece): evidence for fractional crystallization and magma mixing
POLI, Giampiero;
1997
Abstract
The Vrondou intrusive complex is an Oligocene composite pluton, located close to the Greek-Bulgarian border, north of Serres in Central Macedonia, North Greece, which intrudes marbles and schists of the Lower Tectonic Unit of the Western Rhodope Massif. Vrondou magmas were emplaced at 7.5 to 11 .2 Km depth in distinct «batches» in an extensional tectonic regime. Mafic microgranular enclaves with ellipsoidal or irregular shapes, up to 30 cm in diameter, are present only in the north-eastern part of the pluton. In the south-eastern part of the pluton a small elongated gabbro-dioritic body outcrops. The Vrondou rocks range from gabbro to quartz monzonite having as main ferromagnesian minerals hornblende, biotite and clinopyroxene in various amounts. The rocks as a whole cover a large compositional field, ranging from calc-alkaline to shoshonitic with some rocks falling in the field of potassic series. Two groups of enclaves are evident, one above the shoshonitic boundary and one mainly on the calc-alkaline field. On the basis of petrographic and geochemical data the rock-types fall mainly in five groups, having different genetic and evolutionary paths. Gabbro-dioritic rocks of calc-alkaline affinity evolve through cumulus processes at low pressure in a magma chamber. Monzonitic rocks bearing high-K magmatic enclaves have a shoshonitic affinity and evolve through mixing plus fractional crystallization processes between metaluminous granodioritic-monzogranitic anatectic magmas and mantle derived magmas of lamprophyric affinity. Quartz-monzonitic rocks bearing low-K magmatic enclaves straddle the fields of calc-alkaline and high-K calc-alkaline, and evolve through processes of mixing plus fractional crystallization between anatectic magmas, similar to that of monzonite, and mantle-derived magmas of calc-alkaline affi ìnity. Quartz syenite and granite outcropping in the south-western part evolve through various stages of fractional crystallization with different crystallizing assemblages. The parental magmas for the strongly potassic suite were derived by partial melting of an enriched mantle wedge under different conditions of pressure and/or composition, whereas the parental magmas of the calc-alkaline suite were derived from a less enriched mantle wedge under lower pressure. Intrusions of those mantle derived melts underplate the crust, and supply heat to induce the crustal partial melting that produces metaluminous granodioritic-monzogranitic melts.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
