Neoproterozoic and Variscan SHRIMP ages for zircons from the Baba Mountain granitic complex, basement of the Hellenides Alpine orogenic belt

摘要

Zircons from four samples from the Baba Mt. granitic complex yield SHRIMP U-Pb ages ranging from 1.7 Ga to 132 Ma, recording Neoproterozoic (708.2 +- 4.2 - 693.1 +- 4.4 Ma) and Late-Variscan (358.6 +- 3.2-312.2 +- 1.5 Ma) emplacement ages, as well as the Alpine overprint (157.2 +- 0.8, 154 +- 0.8 and 132.4 +- 0.7 Ma). The geochronological results of this study support the notion that the pre-Alpine basement of the Pelagonian zone was formed in at least two distinct episodes. The Neoproterozoic ages, differentiate the leucogranites from the other rock types of this pluton. These rocks are the oldest in the study area and consequently, they cannot be a local differentiation product of the granite as previously assumed. The ages of the leucogranites are identical to those of the newly recognized Fiorina terrane that was lately delineated in the area. According to the geochronological data, the Baba Mt. leucogranites are part of the extended, Late Proterozoic magmatism, along or close to the northern margin of Gondwana. The Late Variscan ages of the Baba Mt. granites and granodiorites point towards the development of a Permo-Carboniferous magmatic arc, resting on the continental basement formed by the Fiorina terrane. The plutonic rocks studied underwent several post-emplacement tectonometamorphic processes, recorded by the zircon ages presented here.