China Discovers Rare Remnants of Old CrustChinese geologists recently found 3.65 billion-year-old remnants of ancient crust in the Aktashitage Hill, eastern part of the Altyn Tagh in Gansu in west China.The discovery makes China one of the four countries in the world that have had such an ancient crust structure. The remnants in Shibaocheng of Subei County in the province are of great scientific value in research and study of earth evolvement, crystal framework, and plate drifting. The remnants, a granite gneiss with 300 meters long, 200 meters wide, and 100 meters thick, were lying in the Aktashitage Hill and 2,636 meters above the sea level. Lu Yongnian, a research fellow with the Tianjin Institute of Geology and Mineral Resources, said it was very rare to discover such an old and a large area of remnants. The newly-discovered remnants are composed of plagioclase, quartz and white mica. According to the latest research results available, the earth is estimated about 4.6 billion years old, with its continental crust of an average 35 km thick. Only Canada, Australia, and the Antarctica have discovered remnants of old crust since the 1980's. Lu said the Aktashitage old crust along the southeastern edge of the Tarim Plate, came into being about four billion years ago. It floated near the equator about one billion years ago, then it drifted to the present position about 180 million years ago and remained there since then. As it is in the joining area of the Qaidam Plate, Tarim Plate and the North China Plate, where non or few people dwell there, the remnants are able to remain intact. China geologists used to discover hypersthene plagioclase granulate in the Taipingzhai, Qianxi County of the northern Hebei province, which has been named by the United Nation's Association of Geochronological Analysis as the "World Rock Originator" which is 3.67 billion years old. But it was a pity that the stone was not existing in the form of old crust. |
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