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

本项目旨在研究格陵兰东南部古元古代那格苏托其甸造山带高压变质岩的压力-温度-时间-变形演化。那格苏托其甸造山带的独特之处在于，它是古元古代少数几个保存有高压变质岩的碰撞造山带之一。残留榴辉岩和/或高磷麻粒岩赋存于造山带以正麻岩为主的核部镁铁质岩墙内。石榴石和单斜辉石以及单斜辉石-斜长石的矿物组合表明斜长石稳定区外的PT-条件。该项目的初步工作表明，这些岩石经历了中高压麻粒岩相级别的退缩，但目前尚不清楚这些岩石是从哪个地壳深度剥离出来的。这项研究将与丹麦和格陵兰岛地质调查局(GEUS)合作，将通过对锆石、金红石和钛矿等矿物进行伪截面模拟和U-Pb测年获得的压力-温度-时间路径与高P区南北剪切带的详细运动学调查相结合。这些资料不仅将对纳格斯苏托-齐甸造山带高压岩石的构造演化和折返历史有新的认识，而且将为中古元古代超大陆努纳形成的地球动力学过程提供约束。

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.