Palaeozoic Orogeneses Around the Siberian Craton : Structure and Evolution of the Patom Belt and Foredeep
The Patom fold and thrust belt draws an arc along the south-eastern edge of the Siberian craton, and is a segment of the Central Asian Orogenic Belt (CAOB) also known as the Altaides. It is supposed to be Caledonian and to result from the accretion of volcanic arcs and microcontinents against the craton. A field study in the Patom foreland and highland allows us to precise the geodynamic history of the area. The observed sedimentary succession confirms the existence of a passive margin setting in the Late Riphean (around 900 Ma), followed during the Vendian (650-600 Ma) by the obduction of the Baikal-Muya ophiolites belt and a foredeep inversion. Then, a period of relative tectonic quiescence is recorded until the main collision stage (post Devonian). The sedimentary record is thus marked by a slow evolution with very long stable periods of more than 250 Ma. We interpret it in the light of the geodynamic evolution of Siberia, which is dominated by successive continental collages against the Siberian craton. The analysis of field data reveals homogeneous directions of compression from the inner metamorphic areas to the outermost foreland domain. But whereas the inner range displays highly deformed rocks and metamorphosed units, deformation is much weaker in the foreland which developed above the cratonic crust. We propose to relate this high deformation gradient to the presence of the stiff craton which impeded strain propagation in the foreland. In addition this gradient, but also the topography, seem to evolve laterally from a strong contrast in the south to more progressive variations in the northern arc. This evolution is consistent with a rather thick-skin tectonic in the south and a thin-skin style in the north. The curved shape of the craton's boundary and the pre-existent basement topography inherited from Palaeoproterozoic rifting stages can explain these different tectonic styles observed along the belt, as well as its particular tightened shape.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 8102 Continental contractional orogenic belts and inversion tectonics;
- 8103 Continental cratons