华北、秦岭及扬子陆块的若干古地磁研究结果

SOME PALEOMAGNETIC RESULTS ON NORTH CHINA, QINLING AND YANGTZE BLOCKS

本文对华北陆块、秦岭陆块以及扬子陆块内的70个采样点,474个标本进行了古地磁研究,利用16个采样点,112个标本中所获得的原生剩磁,重点分析了三陆块自寒武纪以来的古地磁极位置、古地磁偏角以及古纬度的变化特点。结果表明,三陆块为不同地质构造单元;寒武纪以来,华北陆块、秦岭陆块以及扬子陆块自北到南顺序排列;寒武纪时,秦岭陆块北侧和南侧分别存在一古洋盆,此时华北陆块和扬子陆块相距约1060km,三陆块向北漂移的过程中伴随着旋转运动,其中华北陆块和秦岭陆块以反时针旋转占优势,扬子陆块以顺时针旋转占优势;三陆块完全拼合时间在早三叠世至晚白垩世之间。

This paper describes paleomagnetism of 474 specimens from 70 sites in North China Block ,Qinling Orogenic Belt and Yangtze Block. We isolated primary magnetic components from 112 specimens of 16 sites and obtained apparent polar wonder paths (APWP) and variations in paleomagnetic declinations and paleolatitudes of the three zones since the Cambrian. As the result, we demonstrate the following conclusions : ( 1 )The three zones were situated in the present order from the geographic north since the Cambrian : North China Block ,Qinling Orogenic Belt and Yangtze Block ;(2)In the Cambrian period,there was a paleo-ocean on both the northern and the southern sides of paleo-Qinling terrane; (3)At the time,North China Block was situated about 1 060km away in the north from Yangtze Block ; (4 )The three zones moved to the north with tectonic rotation since the Cambrian and were fused together during a period between the Triassic and the Cretaceous.