Grain-scale pressure variations in metamorphic rocks: implications for the interpretation of petrographic observations

Thermodynamic equilibrium at heterogeneous pressure

“…1 in Llana-Funez et al 2012 and Fig. 4 in Tajčmanová et al 2015). Studies of stress perturbations around inclusions involving also plastic deformation investigate the importance of non-homogeneous stress (and pressure) distribution on the formation of shear zones in polymineralic rocks (Misra and Mandal 2007).…”

“…As we use a mass-based approach (see Tajčmanová et al 2014Tajčmanová et al , 2015, phase compositions and energy are converted to weight fraction and J/kg, respectively, by dividing over molecular mass of the phase. Solid solutions are generated as discrete phases systematically varying the composition following an approach similar to Connolly (2005).…”

“…1). The slope of the g-x curves being equivalent to the driving force for diffusion (Δμ, see review in Tajčmanová et al 2015) is equal for both points (Δμ P1 -Δμ P2 = 0). Hence, the system is in thermodynamic equilibrium, and the global minimization approach is equivalent to the chemical potential-based approach.…”

Subduction, peak and multi-stage exhumation metamorphism: Traces from one coesite-bearing eclogite, Tso Morari, western Himalaya

“…In order to shed light upon possible conditions necessary to form magnesite, dolomite, coesite and glaucophane and thus to supplement the reconstruction of the prograde and retrograde PT-path of this eclogite we applied thermodynamic forward modelling taking the effective bulk rock composition, step-by-step corrected for the fractionation effects of zoned garnet during prograde metamorphism (Konrad-Schmolke et al, 2005;Spear, 1988;Tajčmanová et al, 2015; see supplementary material for the initial whole rock composition, the fractionated composition and the complete phase assemblages). Applying the Perple_X668 program (e.g.…”

P-T-t reconstructions of South Yenisei Ridge metamorphic history (Siberian craton): petrological consequences and application to the supercontinental cycles

“…They are formed under different geodynamic conditions, often accompanied by the development of orogeny-and rift-related blastomylonite zones (Ivanov and Rusin, 1997;Mancktelow, 2008;Rusin, 2007), which are of major, but largely underestimated importance for reconstructing of the history of orogenic belts. The data on thermodynamics and timing of syn-shear deformation events at deep crustal levels are rare or absent and the contribution of the deformation component to the energetics during formation of regional metamorphic terranes is thought to be small (Tajcmanova, 2013). It has become apparent recently that syn-shear metamorphic processes play an important role during orogenesis and, therefore, the products of dynamic metamorphism can be applied successfully to the solution of many petrogenetic problems.…”