Cambrian arc-continent collision in the Paleozoides of Kazakhstan

A model of the Cambrian evolution of the Paleozoides in Kazakhstan is presented on the basis of consideration of Cambrian rock complexes. The Middle Cambrian collision of an island arc and a passive continental margin was the main event of this evolution. Three stages of the Paleozoides evolution are recognized in the Cambrian. The first, precollision stage embraces a time span from the Early Cambrian to the first half of the Amgian Age of the Middle Cambrian in which the following elements of the continent-ocean transitional zone may be reconstructed: passive continental margin-backarc basin with oceanic crust-island arc-oceanic basin. At the second, collision stage (the second half of the Amgian Age), the backarc basin was closed and the continental margin and island arc collided, forming a suture zone. At the third, postcollision stage (the Mayan Age of the Middle Cambrian-Early Ordovician), the structure of the convergent margin was complicated. The volcanic belt started to develop on the accreted continental margin. A system of ensimatic island arcs originated at the same time and migrated toward the outer basin. The active rifting was typical of the inner part of the continental margin.