ABSTRACT
Phanerozoic orogenia igneous activity was analogous to that occurring at active plate margins at the present day. However, that of anorogenic areas is believed to have been similar to intra-plate magmatism. Typical evidence for continental magmatic activity in anorogenic areas has been found in areas associated with the development of palaeorift structures associated with ancient platforms. They can be readily identified, presenting no problems in their interpretation. Lyashkevich classified the igneous rocks of the Dnieper–Donets Palaeorift into a number of assemblages, such as: basalt–dolerite; trachybasalt–trachyandesite–trachyrhyolite; melanephelinites, alkali–ultramafics, alkali gabbroids and carbonatites; and tephrites, basanites and phonolites. The Permian Oslo Graben is another good example of a palaeorift. Its geological history dates back to the latest Carboniferous–early Permian. Traps are very extensive areas of intrusive and volcanic rocks, mainly of basic composition, formed on stable cratons.
