Introductory remarks

Abstract

In the past decade or so several major advances have significantly increased our understanding of continental crustal evolution. First, there is widespread recognition that the Wilson Cycle of plate opening and closure was responsible for the formation of Mesozoic-Cainozoic orogenic belts. Indeed the application of this plate tectonic scenario has been so successful that it is now possible to interpret the deformation of most Palaeozoic and several Proterozoic orogenic belts by accretionary or collisional processes. Secondly, there has been a surge of multidisciplinary research activity on Precambrian rocks, and especially on those formed before about 2.5 Ga B .P . during the Archaean. In the light of these advances, we are now beginning to understand the evolution of the continental crust in a continuous, long-term perspective with a global tectonic model that seems to be increasingly applicable to a wide range of young and old environments. This meeting report highlights one of the principal current controversies regarding continental crustal evolution: how much crust was created during, and by the end of, the Archaean, and how much subsequently? This question is directly related to the controversial role of secular recycling of crustal materials. According to one view (Armstrong), based mainly on isotopic and continental freeboard arguments, the total mass of continental crust was differentiated early in the Earth’s history, perhaps before 3.7 Ga B.P ., with negligible crustal growth since that time. This ‘steady-state’ model clearly implies efficient recycling of the bulk of eroded continental materials through the mantle throughout geological time