| Summary: | The Nuuk region is dominated by complexly deformed Archaean TIG orthogneisses with subordinate supracrustal lithologies that have been variably metamorphosed at upper amphibolite to granulite facies. The region is interpreted as a mid- to lower crustal exposure of a Meso- to Neoarchaean terrane complex, collectively affected by high grade deformation and metamorphism between 2720 and 2650Ma. New studies of the previously little-understood Kapisillit area, SE Nuuk region, suggest significant exposures of the recently-proposed Kapisillik terrane, a crustal block characterised by a distinct magmatic and metamorphic history between ca. 3100 Ma and 2650 Ma. A fuller understanding of the tectonic units within the Kapisillit area, including the extent and internal age-event relations of the Kapisillik terrane, thus has important implications for our understanding of the tectonothermal evolution of the Nuuk region. Three field areas were selected in west, east and north Kapisillit (Norsanna, Tummeralik and Aputitooq Mountain respectively). Norsanna is situated at the boundary between the ca. 2825Ma Tre Br~dre and 3800-3300 Ma Freringehavn terranes whereas Tummeralik lies entirely within the proposed Kapisillik terrane. Aputitooq Mountain is situated within 2km of the purported boundary zone between the Freringehavn and Kapsillik terranes. The tectonothermal evolutions of the three areas were investigated using field mapping, metamorphic petrology of pelitic assemblages and UlPb zircon geochronology of key orthogneisses and structurally constrained leucosomes. P-T -t paths for each of these areas were constructed and considered in a regional context through integration with complementary geochronological, structural and metamorphic information obtained in parallel studies conducted both in the Kapisillit area and more broadly in the Nuuk region as a whole. Metamorphic, structural and geochronological data suggest that N orsanna and Tummeralik share a polydeformational history during the Neoarchaean, between ::52817Ma and ...
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