Istituto di Geoscienze e Georisorse     
Venturelli G., Thorpe R., Dal Piaz G., Del Moro A., Potts P. Petrogenesis of calc-alkaline, shoshonitic and associated ultrapotassic Oligocene volcanic rocks from the Northwestern Alps, Italy. In: Contributions To Mineralogy and Petrology, vol. 86 (3) pp. 209 - 220. Springer, 1984.
Along the Western Alps there is geological evidence of late-Alpine (Oligocene) magmatic activity which clearly postdates the Lepontine (Eocene-early Oligocene) metamorphism and related deformation of the Alpine nappe pile. This magmatic activity was notably delayed in relation to the most important convergent processes and may be related to buoyancy of lithosphere, tensional tectonics and thermal updoming subsequent to the collision between the Eurasian and African plates. The geochemical features of the rocks and the geophysical characteristics of the Alpine chain, suggest that: (a) shoshonitic and calcalkaline melts may have been generated by partial melting of metasomatized peridotitic material and subsequent fractional crystallization and crustal contamination; silicic andesites and latites, however, could have been also derived from metasomatized eclogite or deep continental crust material; (b) the ultrapotassic lamprophyres with high K, P, LREE, Th, Zr, U and high ⁸⁷Sr/⁸⁶Sr ratios were generated by partial melting of strongly metasomatized mantle; the varied Sr-isotopic ratios may partially also reflect additional radiogenic component from the continental crust following magma segregation from the source.
URL: http://link.springer.com/journal/410
Subject Italy
Northwestern Alps
Oligocene magmatic activity
volcanic rocks
chemical composition

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