Metamorphic evolution and tectonic significance of high-P metamorphic rocks in the Palaeoproterozoic: the Nagssugtoqidian Orogen, South East Greenland.

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This project aims to investigate the pressure-temperature-time-deformation evolution of high-pressure metamorphic rocks in the Palaeoproterozoic Nagssugtoqidian Orogen in South-East Greenland. The Nagssugtoqidian Orogen is unique in that it is one of a few Palaeoproterozoic collisional orogens, in which high-pressure metamorphic rocks have been preserved. Relict eclogites and/or high-P granulites occur within mafic dykes in the orthogneiss-dominated core of the orogen. Mineral assemblages of garnet and clinopyroxene as well as clinopyroxene-plagioclase symplectites indicate PT-conditions outside the plagioclase stability field. Preliminary work to this project indicates that the rocks underwent retrogression at medium-to high-pressure granulite facies grades, but it is currently unknown from which crustal depth these rocks were exhumed. In collaboration with the Geological Survey of Denmark and Greenland (GEUS), the research will combine pressure-temperature-time paths obtained from pseudosection modelling and U-Pb dating of minerals such as zircon, rutile, and titanite with detailed kinematic investigations of shear zones to the north and south of the high-P domain. The data will not only give new insights into the tectonic evolution and exhumation history of high-pressure rocks in the Nagssugtoqidian Orogen, and will also provide constraints on the geodynamic processes during the formation the supercontinent Nuna in the mid Palaeoproterozoic.