Palaeoproterozoic UHT metamorphism in the Lewisian complex and North Atlantic region

Abstract

Palaeoproterozoic ultra-high temperature (UHT) metamorphism of the Lewisian complex in South Harris and the North Atlantic regions were examined. The characteristic features of the UHT metamorphism in the South Harris can be summarized as a) mineral textures and constituent mineral associations are concordant with anti-clockwise metamorphic history, b) presence of subduction-related various precursory rocks lead to formation of various types of sapphirine-bearing rocks, and c) heat source that established UHT metamorpism in South Harris is the emplacement of igneous suite in the magmatic arc at c. 2.18-1.87 Ga. In the North Atlantic region, possible UHT metamorphism were reported from the Boothia-Somerset granulite terrane, Taltson-Thelon orogen and Kolvista-Umba zone during 1.9-2.0 Ga. Precise correlation between UHT in South Harris and these terranes are not clear, although magmatic arc or island arc are considered to be reasonable tectonic setting for the UHT metamorphism in the Palaeoproterozoic North Atlantic region.