Strain and deformation history in a syntectonic pluton. The case of the Roses granodiorite (Cap de Creus, Eastern Pyrenees)

Abstract

The Roses granodiorite is a Variscan stock with well developed syn- and post-magmatic deformation structures that crops out in the Pyrenean Axial Zone. Analysis of structures reveals a continuous deformation history during and after magma cooling. The deformation history is divided on the basis of mechanical behaviour into two stages: an early one with the development of magmatic structures and a late stage with the development of mylonitic fabrics along shear zones. Both stages are separated in time by the emplacement of aplite-pegmatite dykes. Time of dyke emplacement is thought to coincide with a sudden change in rheology of the granodiorite. The abundance of quartz dioritic enclaves permits the use of shape analysis to characterize the magmatic fabric as a homogeneous deformation. Later solid-state deformation led to the development of an inhomogeneous deformation pattern with different sizes of anastomosing shear zones wrapping around lozenge-shaped domains. The displacement/width ratio measured in shear zones ranges between one and two orders of magnitude. The Roses granodiorite is thought to be a synkinematically emplaced stock which records a continuous deformatioinal history with two distinct deformation stages, both recording bulk finite strains of similar order of magnitude but with a marked difference in finite strain distribution.

Vertical strain partitioning in hot Variscan crust: Syn-convergence escape of the Pyrenees in the Iberian-Armorican syntax

“…In the Axial Zone, extension was interpreted to have taken place before (Soula et al, 1986a), during (Mezger and Passchier, 2003) or after (Van den Eeckhout and Zwart, 1988;Vissers, 1992) shortening of the superstructure. In the eastern Pyrenees, HT deformation and magmatism have been shown to be coeval with regional-scale dextral-reverse shear zones (Carreras and Capella, 1994), in agreement with synkinematic emplacement of the plutons in the superstructure in an dextral transpressional context (Bouchez and Gleizes, 1995;Gleizes et al, 1998aGleizes et al, , 2001Gleizes et al, , 2006Aurejac et al, 2004;Carreras et al, 2004;Román-Berdiel et al, 2004. Recent structural analysis of the Aston, Hospitalet and Bossost domes (Fig.…”

Zipper junctions: A new approach to the intersections of conjugate strike-slip faults

“…We describe here an outcrop-scale example of two shear zones in the process of zippering up to form an extraction fault, as evidence that this process can occur on the small scale and to document the pattern of displacements. Cap de Creus in northeast Spain is a region of late Paleozoic deformation that contains numerous dextral and sinistral shear zones that were active at the same time (Carreras et al, 2004(Carreras et al, , 2010. In several places, shear zones with opposite senses merge by zippering up (Passchier and Platt, 2016), one of which is shown in Figure 5.…”

Temperature, fluid content and rheology of localized ductile shear zones in subsolidus cooling plutons

“…During this subsolidus cooling path, localized deformation structures trigger the retrograde metamorphic re‐equilibration of the magmatic pluton, similarly to what occurs during regional orogenic retrograde metamorphism over a larger (10 6 –10 7 years) temporal scale (Holness, Clemens, & Vernon, 2018; McBirney, 2009). Indeed, the subsolidus deformation structures developed within granitoid plutons are commonly adopted as rheological proxies for the deformation of the quartzofeldspathic continental crust at different structural levels (Bestmann & Pennacchioni, 2015; Buettner, 1999; Caggianelli, Ranalli, Lavecchia, Liotta, & Dini, 2014; Carreras, Druguet, Griera, & Soldevila, 2004; Ceccato & Pennacchioni, 2018; Ciancaleoni & Marquer, 2006; Fitz Gerald, & Stünitz, 1993; Gapais, 1989; Gapais & Barbarin, 1986; Guastoni, Pennacchioni, Pozzi, Fioretti, & Walter, 2014; Ingles, Lamouroux, Soula, Guerrero, & Debat, 1999; Liotta, Festa, Caggianelli, Prosser, & Pascazio, 2004; Marsh, Johnson, Yates, & West, 2009; McCaffrey, 1994; Michibayashi & Masuda, 1993; Nevitt, Warren, Kidder, & Pollard, 2017; Pennacchioni et al., 2006; Pennacchioni, Menegon, Leiss, Nestola, & Bromiley, 2010; Pennacchioni & Zucchi, 2013; Takagi, Goto, & Shigematsu, 2000; Tribe & D’Lemos, 1996; Tschegg & Grasemann, 2009; Tullis, 2002). A characteristic feature of many cooling plutons is the development of small‐scale (cm–dm–thick) localized ductile shear zones that exploit precursory structures, such as joints, dykes and veins, post‐dating homogeneously distributed strain and preceding brittle faulting (Carreras et al., 2004; Ceccato & Pennacchioni, 2018; Guastoni et al., 2014; Pennacchioni, 2005; Pennacchioni et al., 2006; Pennacchioni & Zucchi, 2013; Tribe & D’Lemos, 1996).…”