Okhotsk-Chukotsk Fold Belt and the Problem of Volcanic Arcs in Northeast Asia1
Published:January 01, 1973
The East Asian system of volcanic belts is situated between the area of Cenozoic folding in the northeast Circum-Pacific region and more ancient, mainly Mesozoic tectonic zones. The extent of the East Asian volcanic system is comparable to that of recent volcanic arcs.
The largest element of the East Asian system, the Okhotsk volcanic belt, contains structures characteristic of those of the marginal volcanic belts. The basic features of the belt were formed during the Aptian-Albian and Cenomanian-Turonian. During that time period, andesite volcanism prevailed, although granitoid magmatism was widespread and was accompanied by the formation of ignimbrite fields of large volume.
Comparative structural, petrologie, and historic-geologic analyses have revealed considerable differences between the Okhotsk-Chukotsk belt and the Kuril-Kamchatka volcanic arc.
A specific zone of intensive uplift and subaerial, mainly andesite volcanism was stabilized in the structures of the basement of the Okhotsk-Chukotsk belt. Formation of this zone was simultaneous with the deep-seated faulting which separated the Verkhoyansk-Chukotsk and the Koryak-Kamchatka géosynclinal regions in the Mesozoic. During the Late Jurassic and the first half of the Early Cretaceous, the Okhotsk-Chukotsk volcanic zone (in relation to the mentioned regions) had the same function as does the Kuril-Kamchatka volcanic arc today in relation to Kamchatka, the Okhotsk Sea, and Hokkaido, on one side, and the Kuril-Kamchatka trench on the other.
The presumably Late Jurassic-Early Cretaceous volcanic arc was a peculiar bordering structure which separated the Anadyr'-Koryak géosynclinal system (in an early stage of its development) from the Ver-khoyansk-Chukotsk region of Mesozoic folding (in the epigeosynclinal stage of orogenesis). Development of the Okhotsk-Chukotsk marginal volcanic belt began in Aptian-Albian time—when a considerable volume of terrigenous sediment was accumulating in the Anadyr'-Koryak géosynclinal system, and the Verkhoyansk-Chu-kotsk area represented part of a continental block with a tendency to rise. The volcanic belt included not only the volcanic arc, but also extended far beyond—over Mesozoic fold structures, ancient rigid massifs, and the peripheral zone of the Anadyr'-Koryak géosynclinal system.
Gradual migration of volcanic arcs toward the Pacific did not occur in Northeast Asia. Their appearance and development in space and time bore an uneven character. The development and the nature of the mentioned structures are important tectonic aspects of the general problem of andesite volcanism.
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Following the discovery of Prudhoe Bay oil field in 1968, much attention was turned to the Arctic in the search for giant hydrocarbon accumulations. The Soviets had already proved giant reserves in their West Siberian Basin, and exploration was moving ahead quickly in the Canadian Arctic. Plans were drawn up for an AAPG Symposium on Arctic Geology and held in February 1971. Papers were selected from the Symposium for this publication and cover seven topical groupings: Regional Arctic Geology of Canada, Regional Arctic Geology of the Nordic Countries, Regional Arctic Geology of the USSR, Regional Arctic Geology of Alaska, Comparisons in the North Atlantic Borders, Evolution of the Arctic Ocean Basin, and Economics of Petroleum Exploration and Production in the Arctic.