Strain-rate estimation of syn-tectonic plutonic rocks: a multiple approach combining paleopiezometry, flow law and PT pseudosection

The Symvolon pluton was syn-tectonically emplaced at 22 Ma (Dinter et al., 1995) in the southern part of the Rhodope Core Complex (southeastern Greece) along an extensional shear zone. It mainly consists of granodiorites, which were affected by ductile deformation during cooling, showing an increasing strain gradient approaching the hosting Hercynian gneisses (Punturo et al., 2014). The NE-SW elongated shape of the pluton reflects strong regional scale tectonic control (Brun & Sokoutis, 2007); mesoscopic structural features such as mylonitic foliation and stretching lineation are averagely oriented (dip direction/dip) 290°/15° and 75°/10° respectively. A quantitative microstructural analysis of quartz domains was performed on samples collected along a transect oriented roughly perpendicular to the long axis of the pluton ( from the pluton centre to the periphery). PT shear conditions were estimated by thermodynamic equilibria of syn-shearing assemblages via pseudosection tool. These estimates, in combination with quartz paleopiezometer and flow law, allowed us to infer the strain rate for these syn-tectonic intrusive rocks.