Determination of Structural Successions in Migmatites and Gneisses

This book has been written in response to While considerable effort has been made to requests from a number of colleagues in the ensure that the coverage is comprehensive, it is earth sciences in different parts of the world. not necessarily exhaustive. Prominent among these are geologists whose The importance attached to the structural interests lie in the fields of isotopic and analysis of migmatites (and other complex economic geology and who have a particu­ structural associations) stems from the fact larly keen appreciation of the importance to that resolution of their structural complexity their work of a thorough understanding of the has such a significant bearing on many aspects structural relationships in rocks, especially of geology, both academic and economic. where such rocks, like migmatites, have a long Examples of some of these applications are and often complex developmental history. listed in Chapter 14. Two particularly impor­ What these geologists asked for was a guide tant aspects are that the structural characteris­ to the methods employed in resolving the struc­ tics so identified can be used (1) to correlate tural complexity of repeatedly deformed rocks between separated rock units with comparable (i. e. those affected by 'polyphase' or multiple deformational histories, including segments deformation), especially in Precambrian base­ of fragmented supercontinents, and (2) to ment terranes.