Emplacement of the Arzachena Pluton (Corsica–Sardinia Batholith) and the geodynamics of incoming Pangaea Leonardo Casini a, ⁎, Stefano Cuccuru a , Matteo Maino b , Giacomo Oggiano a , Massimo Tiepolo c a Università di Sassari, DiSBEG, via Piandanna n°4, 07100 Sassari Italy b Università di Pavia, Earth Science Department, via Ferrata n°1, 27100 Pavia Italy c CNR, Istituto di Geoscienze e Georisorse, via Ferrata n°1, 27100 Pavia Italy abstract article info Article history: Received 8 November 2011 Received in revised form 21 March 2012 Accepted 23 March 2012 Available online xxxx Keywords: Anatexis Pluton emplacement Strike-slip shear zones U–Pb zircon dating Corsica–Sardinia Batholith Variscan The assembly of the Corsica–Sardinia Batholith (C–SB) coincides with final shaping of the Variscan belt and represents a key structure to unravel the feedbacks between partial melting, rheology and the evolution of collisional orogens. This paper presents a model for the genesis of the Arzachena pluton (AZN), one of the major calc-alkaline massifs of the C–SB, based on U–Pb zircon dating, thermobarometry and structural analysis. Major and trace element compositions indicate that AZN has hybrid characteristics between that of typical S- and I-type granites, that could be explained in terms of incremental melting of a heterogeneous crustal source made of metatexites and Ordovician calc-alkaline granitoids. Growth of the pluton started around 320–315 Ma with the emplacement at middle crustal level (0.37–0.4 GPa) of granodioritic melts within narrow, conjugate, NW–SE sinistral and E–W dextral shear zones. The main growth stage (311 + 6/-4 Ma) is marked by emplacement of large volumes of monzogranitic melts that induced a local decrease of the crustal strength expressed by horizontal channel flow driven by the gravity. Finally (307.6±3.5 Ma), leucogranites emplaced within radial and peripheral dilatant fractures developed during the cooling of the main body. The transition from magmatic to sub-magmatic and HT-solid state fabric observed throughout AZN indicates that deformation plays a non-trivial role during the growth of the magmatic system. Restoring the position of the Corsica–Sardinia block to early Permian coordinates allow to recast the birth of the C–SB in a consistent geodynamic framework that conciliates the development of conjugates strike-slip structures, the oroclinal bending of the chain and the thermal relaxation. This study indicates that the C–SB had an active role during post-orogenic extension rather than being just a consequence of it. © 2012 Elsevier B.V. All rights reserved. 1. Introduction During crustal thickening and mountain building, rock may become hot enough to start melting; the presence of low-viscosity, partially molten layers in the continental crust yields to a drastic drop of the lithosphere strength, causing rocks to experience high-grade metamorphic deformations (e.g. Jamieson et al., 2011). The most obvious large-scale evidences for the presence of melts within the continental crust are the development of granitic batholiths. Rock melting and the formation of localized plutons, however, happen not just during crustal shortening, but under a series of tectonic settings, including extension and rift propagation; (e.g. Vanderhaeghe, 2009); although the presence of plutons does not, therefore, indicate a specific geodynamic setting, it provides an indisputable record of melt-present deformation. The South-European Variscan Realm (Rossi et al., 2009) is commonly considered as a reference example for ‘hot’ collisional chains, in which crustal anatexis, granite emplacement and high-T metamorphism all contributed to determine the tectonic style of the mountain belt (Gébelin et al., 2009). The processes that define and control the relationships between ductile deformation and partial melting can be investigated in north Sardinia, where a complete section of the deep crust intruded by the Corsica–Sardinia Batholith (C–SB) is particularly well exposed (C–SB, Orsini, 1976; Rossi and Cocherie, 1991). Over the past decades, it has been demonstrated that decompression-related melting played a major role during the formation of the C–SB (Rossi and Cocherie, 1991; Ferré and Leake, 2001). Crustal extension may effectively results in a pronounced thermal anomaly that have the potential for generating melts in the uppermost subcontinental mantle, and also in the felsic lower crust by self-feeding mechanisms (Ferré and Leake, 2001). Yet, most authors interpreted the origin of the C–SB purely in terms of post-collisional gravitational collapse of the mountain chain (Carmignani et al., 1994; Ferré and Leake, 2001; Bussy et al., 2000; von Raumer et al., 2003). A model of generalized vertical shortening account for the generation of hybrid magmas during progressive decompression, however it fails to Tectonophysics xxx (2012) xxx–xxx ⁎ Corresponding author. Tel.: + 39 079 228633. E-mail addresses: casini@uniss.it (L. Casini), scuccuru@uniss.it (S. Cuccuru), matteo.maino@unipv.it (M. Maino), giacoggi@uniss.it (G. Oggiano), tiepolo@crystal.unipv.it (M. Tiepolo). TECTO-125423; No of Pages 19 0040-1951/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.tecto.2012.03.028 Contents lists available at SciVerse ScienceDirect Tectonophysics journal homepage: www.elsevier.com/locate/tecto Please cite this article as: Casini, L., et al., Emplacement of the Arzachena Pluton (Corsica–Sardinia Batholith) and the geodynamics of incoming Pangaea, Tectonophysics (2012), doi:10.1016/j.tecto.2012.03.028