中朝板块晚古生代的古地磁特征

中朝板块及其北部的西伯利亚板块,是亚洲东部晚古生代的两大古板块。近年来的地质工作陆续发现,在中朝板块之北侧的索伦山—二连以东地区,存在着晚古生代的大洋壳残余。这表明,在晚古生代的一个时期中,中朝古板块和西伯利亚古板块之间曾一度被大洋所隔。

PALEOMAGNETIC FEATURES OFSINO-KOREA PLATE IN LATE PALEOZOIC ERA

/With a view to further ascertaining tie relative position of the Sino-Korea Plate in late Paleozoic Era and investigating the migration of various plates in Asia, a total of 70 paleomagnetic hand specimens of Carboniferous and Permian sediments were collected along the Qiligou section and the West Valley (Due-rping) section at Xishan, Taiyuan on Shanxi anteclise which, lying in the middle of the North China Platform, were relatively stable during the late evolution stage of the platform. These hand specimens were cut into 140 samples which, after being subjected to heating demagnetization, were measured for remanent magnetization one by one. The average magnetization, paleolatitude and paleopole for every sampling site were thus obtained.The data acquired indicate the following facts. (1) Average paleolatitude of sampling sites during Permian was 24.9° and the difference in latitude between Sino-Korea Plate and Siberia Plate at that time was about 1200km larger than the present difference; paleolatitude in Carboniferous was averagely 16.2° and the difference in latitude between these two plates was some 2100km larger than the present difference. It is tentatively presumed that the Sino-Korea Plate must have lain within low-latitude area in late Paleozoic, in the process of migration from low latitude to high latitude. (2) The formerly-defined Permian strata are of negative polarity with the exception of the middle portion of Shiqianfeng Formation which possesses positive polarity. This formation, according to a comparison of documents available, is preliminarily assigned to Triassic.