Palaeozoic accretionary and convergent tectonics of the southern Altaids: implications for the growth of Central Asia

The southern Altaids present a unidirectional section from Mongolia to China through an accretionary orogen that youngs progressively from Neoproterozoic in the north to Permian in the south. The orogen formed by foreare accretion of island arcs, accretionary wedges, ophiolites and Precambrian microcontinents. This regularity was upset by early growth within the ocean of arcs that later collided at the accreting continental margin, by imbrication of old ophiolites with young arcs, and by Himalayan-style thrust-nappe tectonics when an arc collided into a microcontinent. Lateral growth of the Southern Altaids represents a massive addition of juvenile material to the Palaeozoic crust.