1 3 Int J Earth Sci (Geol Rundsch) DOI 10.1007/s00531-014-1104-8 ORIGINAL PAPER Detrital zircon geochronology in blueschist-facies meta-conglomerates from the Western Alps: implications for the late Carboniferous to early Permian palaeogeography Paola Manzotti · Marc Poujol · Michel Ballèvre Received: 29 April 2014 / Accepted: 1 November 2014 © Springer-Verlag Berlin Heidelberg 2014 Zone Houillère basin or alternatively may represent a small basin, located on the east of the Zone Houillère. Keywords Money Unit · Gran Paradiso · Permo- Carboniferous evolution · Detrital zircon Introduction The late Palaeozoic history of southern Europe is character- ized by three main geodynamic events: (i) the convergence between major plates (Gondwana and Eurasia) leading to the Variscan orogeny (Devonian-early to late Carbonif- erous), (ii) a drastic change in the plate kinematics (late Carboniferous-early Permian) resulting in the transforma- tion of the Gondwana-Eurasia collisional margin into a dif- fuse dextral transform margin, recorded by the orogenic collapse, and (iii) the opening of the Neotethys Ocean during the Middle-Upper Permian, recorded by the pro- gressive westward marine ingression (von Raumer 1998; Cassinis et al. 2012; von Raumer 2013). This evolution was also marked by a progressive change in the climate, which became drier across Europe (Kutzbach and Ziegler 1993; Schönlaub 1993; Schneider et al. 2006). The records of these geodynamic events and of this climate change are preserved in detrital sediments, at present located in differ- ent sectors of the Western and Central Alps (Fig. 1; Supple- mentary data Table 1). In the External Zone (External Massifs and Helvetic nappes) of the Alpine belt, numerous Carboniferous basins of small sizes occur, such as the La Mure basin in the Belledonne Massif (Gignoux and Moret 1952) and the Salvan-Dorenaz basin in the Aiguilles Rouges Massif (Niklaus and Wetzel 1996; Brousmiche Delcambre et al. 1999). In the frontal part of the Briançonnais domain, the Abstract In the Western Alps, the Money Complex of the Gran Paradiso Massif, metamorphosed under blueschist facies during the Alpine cycle, is considered to be Permo- Carboniferous in age, but no palaeontological or radio- metric data constrain this interpretation. A revision of the lithostratigraphy of the Money Complex allows recogniz- ing a polygenic (graphite-rich) and a monogenic (graphite- poor) meta-sedimentary formation. Detrital zircon U–Pb geochronology in both meta-sedimentary formations shows that (i) the main population is Cambrian and Ordovician in age, (ii) the youngest grains are Silurian and Lower Devo- nian, and (iii) Carboniferous zircon grains are lacking. A careful study of the age distributions in the Alps suggests that potential source for the detrital material in the Money Complex is the Briançonnais basement. Late Carboniferous magmatism is widespread in the Helvetic Zone of the Alps. Permian magmatism is dominant in the Briançonnais, the Austroalpine and the Southalpine basements. The lack of Carboniferous zircons in the Money Complex suggests that the detritus was not shed from the Helvetic zone, which was separated from the Money basin by the Zone Houillère basin, where the main drainage pattern was developed from south to north and where the depocenters migrated north- wards from the Upper Missisippian to Upper Pennsylva- nian. We suggest that the Money Complex may had been located to the east of the main river drainage inside the Electronic supplementary material The online version of this article (doi:10.1007/s00531-014-1104-8) contains supplementary material, which is available to authorized users. P. Manzotti (*) · M. Poujol · M. Ballèvre Géosciences Rennes, UMR-CNRS 6118, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France e-mail: paola.manzotti@univ-rennes1.fr