Yenisey Fold Belt

The Yenisey Fold Belt is a fold belt in Russia that divides the Siberian craton from the West Siberian basin, extending about 700 kilometres (430 mi),[1] with NW-SE strike. This belt is divided into northern and southern regions by the Angara fault which has left slip.[2] Much of the rock was formed by Neoproterozoic accretion.[1]

North of the fault, the area is made up of thrust sheets[2] divided into three primarily Neoproterozoic terranes, the East Angara, Central Angara and the Isakov.[1] The Isakov Terrane is a series of imbricated volcanic and sedimentary units containing ophiolite, which is underlain be volcanics, metamorphics and sedimentary rock. Unconformably overlying it is the Vorogovka group, a series of basins which were thrust over the Isakov.[3] This terrane overlies the Central Angara terrane, having been thrust eastward over it.[2] The Central Angara Terrane is intruded by alkaline granites with NNW trend in the elongated bodies. The Eastern Terrane lacks signs of magmatism,[4] instead it is made up of overriding late Neoproterozoic deposits above older groups, most of which are intruded by granites.[3]

South of the Angara fault, there are two allochthonous units. One is the Angara-Kan micro-craton, which is sometimes considered separate from the fold belt.[4] This terrane is formed of Paleoproterozoic granulite amphibolite facies,[2] and the other is the Predivinsk terrane which is mostly Neoproterozoic island-arc accretion.[1] The Angara-Kan terrane also includes two pyroxene plagioclase and one garnet-biotite-sillimanite-cordierite gneisses.[2]

The late Riphean strata of the Sukhopit, Tungusik, and Oslyan series formed on along a continental margin of open ocean followed by a back-arc basin from 1050-1150 million years ago.[5] From around 860-880 MA until 700-630 MA, the collision of many of the terranes occurred during the Baikal orogeny, which was the period of much of the accretion, thrusting, and metamorphism.[6] This period is also when granitic intrusions occurred.