Introduction

Abstract

The average composition of the continental crust is granodioritic (Clarke, 1991) and in some orogenic belts granites form as much as 30% of the surface outcrop and are an essential component of the continental crust. Although they occur in great belts which commonly extend for hundreds or even thousands of miles, each belt is made up of individual bodies,which may be very large, or quite small, and which are invariably rather complex. Until recently granite studies were mainly pursued on such individual bodies by individual geologists resulting in a patchwork of information which, while excellent in itself, has merely dealt with the tip of the iceberg in relation to the problem as a whole. Understanding the geology of our globe requires a much more comprehensive picture of the granites, which form so large proportion of the crust. This can only be achieved by studying them in a regional way, and is all the more necessary since granites result from plate tectonic processes which both produce new crust, and recycle older crust.