In the study of metamorphic rocks exposed in orogenic belts, the high-temperature (HT) - high-pressure (HP) units have been in the center of attention for many decades, thus their tectono-metamorphic significance has been defined with good approximation. In contrast, very low- and low-grade units (peak T< 500°C) gained increasing attention only recently, as their PTDt evolution and tectonic significance during subduction and collision processes is still poorly constrained.
Metamorphic rocks that record LT-blueschist and -greenschist facies conditions and rocks affected by late-orogenic (hydrothermal) fluid circulation are still a challenging research topic due to the frequent lack of equilibrium of metamorphic reactions, small-scale minerals and common mineralogical/geochemical inheritance from protoliths. Rapid technological progress in recent years that allows for high-resolution analysis at micro- to nanoscale facilitates the application of modern analytical methods (e.g. pseudosection modelling, in situ isotopic dating, fluid inclusion studies) on low-grade metamorphic rocks, thus shedding light on their tectono-metamorphic significance in orogenic belts.
This session aims to present the state-of-the-art research focusing on processes activated at upper- to midcrustal levels during orogeny and deciphering PTDt trajectories of very low- and low-grade metamorphic units. Interdisciplinary approaches covering structural, petrological, geochemical and geochronological aspects both on natural samples and experiments that contribute to unravel the tectonic evolution of an orogen are particularly welcome.