Geology of Chukotka, Kolyma and
K: Koni Mugal volcanic belt; OB: Okhotsk block; OCVB: Okhotsk-Chukotka Volcanic belt;
SA: Southern Anui Suture zone
Schematic tectonics of the Magadan-Chukotka area.
Northeast Russia in a geological sense is located east of the Siberian Craton. Politically it comprises the northeastern part of Yakutia, Magadan Obast and Chukotka. The tectonic history of the area is rather complex and not yet fully understood. The main geological units in the area today are the following:
Verkhoyansk fold belt
The Verkhoyansk fold belt is located in eastern Yakutia and part of the Magadan oblast. It is situated between the Siberian craton in the west and the Kolyma-Omolon superterrane. The Verkhoyansk fold belt is composed of sediments, deposited along the margins of the Siberian craton. It's age is Mississipian to early cretaceous.
This unit is situated in the central to northern part of the Magadan oblast. The Kolyma-Omolon superterrane is a jigsaw of several microcontinantal fragments, called blocks. Examples of such blocks are the Omolon block in the southeast and the Prikolyma block just west of the Omolon block, while the Omuliovka block is located more to the southwest. All these blocks are covered by paleozoic to cretaceous sediments. The individual blocks are separated by late Paleozoic to Mesozoic fault and shear zones.
The Chukotka terrane is along the northern shore of Chukotka, inlcuding Wrangell Island.
South Anui Suture zone
The South Anui suture is located between the Kolyma-Omolon superterrane and the Chukotka terrane. In fact the South Anui Zone is the result of classic collision of continents, as can also be seen in the Urals. In this case the collision between the Siberian continent and the Chukotka terrane. Before the collision there was a rift zone.
Okhotsk-Chukotka volcanic Belt (OCVB)
The OCVB is of cretaceous age. The OCVB is situated along the northern shore of the Sea of Okhotsk and can be followed further northeast all the way to to area of Anadyr at the Bering Strait. The belt has a length of about 3200km and consist of volcanic and plutonic rocks. In cretaceous times this belt was a subduction zone. Present day Kamchatka and the sea of Okhotsk where pushed northwards and subducted under the exsisting terranes.
Koni-Mugal volcanic belt
The Koni-Mugal volcanic belt is situated southeast of Magadan and south of the OCVB.
The Okhotsk block is situated southeast of the Verkhoyansk fold belt. It is only a small structure.
New 40Ar/39Ar ages of Cretaceous continental volcanics from Central Chukotka: implications for initiation and duration of volcanism within the northern part of the Okhotsk Chukotka Volcanic Belt (northeastern Russia), by V.O. Ispolatov et al, Journal of Geology, october 2003.
South Anyui suture, northeast Arctic Russia:Facts and problems, by S.D. Sokolov et al, Geological Soc. of America Special Paper 360, 2002, pp209-224