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North China Craton
The North China Craton is one of the smaller continental cratons of Earth. It covers a total area of around 1.7 million square kilometres (655,500 square miles) in northeastern China, northern Korea and the southern part of Mongolia, and has a shape quite akin to a funnel, with a long east-west axis in the western part and two shorter perpendicular axes in the eastern half.
==Geological history==
The North China Craton is composed of several major blocks that have been heavily tilted and folded over time as a result of collisions with other continental land masses. The main blocks include the Eastern Block, the Western Block and the Central Orogenic Belt. The Central Orogenic Belt runs from western Liaoning through Beijing municipality to western Henan and contains chiefly igneous rocks of Paleoproterozoic age. The Western Block extends west from this region through Shanxi, Shaanxi, Inner Mongolia and northern Gansu. This block is the oldest and most stable part of the Craton and contains some of the oldest and mineralogically most valuable rocks in Asia, especially in Inner Mongolia where huge deposits of coal and iron ore are found.
The Eastern Block is unusual for a craton in that it is affected severely by crustal thinning that began in the Mesozoic and is known to have reduced the thickness of the crust from 200 kilometres to as little as 80 kilometres. In the Changbai Mountains and Shandong there has been extensive volcanism in the Tertiary. The crustal thinning of the Eastern Block is believed to be due to high heat flow within the plates (especially the Pacific Plate) surrounding the North China Craton.
Prior to the Triassic, the North China Craton was an independent continent surrounded by oceans. For most of the Paleozoic, it was located near the north pole, often being the northernmost land in the world until it collided with Siberia to comprise the last stage in the formation of Pangaea during the Triassic.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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