Rb/Sr radiometric data from medium- to high-grade metamorphic rocks (Aspromonte nappe) of the north-eastern Peloritani Mountains (Calabrian Arc), Italy
Atzori, Piero; Del Moro, Aldo; Rottura, Alessandro
European Journal of Mineralogy Volume 2 Number 3 (1990), p. 363 - 372
published: Jun 21, 1990
manuscript accepted: Feb 15, 1990
manuscript received: Jan 27, 1989
ArtNo. ESP147050203014, Price: 29.00 €
Abstract Rb/Sr whole-rock and mica analyses were carried out on paragneisses and augen orthogneisses from the north-eastern Peloritani (Sicily), in order to investigate the Hercynian tectono-metamorphic evolution of the basement terrain in this segment of the Calabrian Arc. Whole-rock radiometric data from six small slabs of a migmatitic paragneiss and seven orthogneiss samples do not define isochrons, so it was impossible to date either the emplacement of the protoliths of the orthogneisses or the peak of the amphibolite-facies metamorphism that affected the protoliths. Biotite and muscovite ages in the range 292-262 Ma suggest an uplift of the investigated basement, contemporaneous with the emplacement of associated post-tectonic peraluminous granites. The younger biotite dates (173-137 Ma), obtained from unsheared paragneisses in the Milazzo area collected near a mylonite zone, may reflect later disturbance involving only partial resetting. They suggest that Alpine shear effects, found throughout southern Calabria, also occurred in the Peloritani sector of the Calabrian Arc. The Sr isotopic compositions of the studied metamorphites, recalculated back to the intrusion age of the associated Hercynian S-type granites, are significantly higher than those of the granites (> .0716 vs - 0.710). Therefore the gneisses or similar basement rocks can be excluded as a dominant component in the source region of the granites.