The authors report data on REE, Th, Sc, Rb and Sr on 8 granodiorite samples from the Cima di Vila pluton. Sc varies between 2.7 and 11 ppm, showing a slight decrease with increasing D.I.; Rb varies between 117 and 149 ppm, increasing with increasing D.I.; Th varies between 7 and 16.5 ppm and shows no relationship with varying D.I.; Sr shows high values ( 418- 703 ppm) which increase markedly with increasing D.I.; the patterns of the chondrite-normalized REE show hi gh fractionation for both light and heavy rare earths, with weak but significant negative Eu anomalies in some samples. The data obtained on the Cima di Vila granodiorites show that evolution by simple fractional crystallization from tonalites outcropping in the nearby Vedrette di Ries pluton must be ruled out. Instead these data may be fitted into a generic model according to which the granodiorites studied are the product of various degrees of melting of a garnet-containing rock source. The geochemical variations and different Sr isotopic ratios observed in the Cima di Vila granodiorites and in the Vedrette di Ries tonalites may be explained by means of two alternative hypotheses: a) a compositionally different source of magmas; b) different degrees of partial melting of the same rock source and later modification of the Sr isotopic ratio during rise through the crust, owing to assimilation processes.
Ree distribution in the Cima di Vila (Sinnock) granodiorite complex and its petrogenetic significance (Eastern Alps, Italy)
PECCERILLO, Angelo;POLI, Giampiero
1982
Abstract
The authors report data on REE, Th, Sc, Rb and Sr on 8 granodiorite samples from the Cima di Vila pluton. Sc varies between 2.7 and 11 ppm, showing a slight decrease with increasing D.I.; Rb varies between 117 and 149 ppm, increasing with increasing D.I.; Th varies between 7 and 16.5 ppm and shows no relationship with varying D.I.; Sr shows high values ( 418- 703 ppm) which increase markedly with increasing D.I.; the patterns of the chondrite-normalized REE show hi gh fractionation for both light and heavy rare earths, with weak but significant negative Eu anomalies in some samples. The data obtained on the Cima di Vila granodiorites show that evolution by simple fractional crystallization from tonalites outcropping in the nearby Vedrette di Ries pluton must be ruled out. Instead these data may be fitted into a generic model according to which the granodiorites studied are the product of various degrees of melting of a garnet-containing rock source. The geochemical variations and different Sr isotopic ratios observed in the Cima di Vila granodiorites and in the Vedrette di Ries tonalites may be explained by means of two alternative hypotheses: a) a compositionally different source of magmas; b) different degrees of partial melting of the same rock source and later modification of the Sr isotopic ratio during rise through the crust, owing to assimilation processes.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
