甘肃玉门地区二叠系—三叠系古地磁研究

Paleomagnetic Study of the Permian—Triassic in the Yumen Area, Gansu

玉门大山口—白杨河一带古地磁研究结果 :下二叠统的特征磁化方向为 Ds=10 8.1°,Is=- 4 6 .1°;极点位置为λ=30 .5°N,φ=18.6°;古纬度为 2 7.6°N。上二叠统的特征磁化方向为 Ds=139.4°,Is=- 4 7.4°;极点位置为λ=5 4 .7N,φ=35 9.9°;古纬度为 2 8.2°N;下三叠统的特征磁化方向为 Ds=15 0 .8°,Is=- 4 8.1°;极点位置为λ=6 3.7°N,φ=35 1.1°;古纬度为 2 9.1°N。说明二叠纪玉门地区所在的阿拉善地块已是华北地块的一部分 ,晚二叠世—早三叠世华北地块大体处于吐哈地块和华南地块之间 ,与俄罗斯地块的古纬度相近 ;华北、吐鲁番—哈密和塔里木地块都大体位于劳亚大陆的东南部。

Paleomagnetic study carried out in the Dashankou—Baiyanghe area of Yumen,the Gansu province of Norfh China shows that the Lower Permian has a characteristic direction of Ds=108.1°, Is=-46.1°, pole position: λ=30.5°N, φ=18.6°, paleolatitude: 27.6°; the Upper Permian has a characteristic magnetic direction of Ds=139.4°, Is=-47.4°, pole position: λ=54.7°N, φ=359.9°, paleolatitude:28.2N; the Lower Triassic has a characteristic magnetic direction of Ds=150.8°, Is=48.1°, pole position: λ=63.7°N, φ=351.1°, Paleolatitude:29.1N°. These data indicate that the Alxa block, to which the Yumen area belongs, was already a part of the North China block during the Late Permian to Early Triassic, the North China block was located rougyly between the Turpan—Hami block and the South China block,and had a paleolatitudinal position similar to the Russian block; the Nouth China, Turpan—Hami and Tarim blocks were all located in southeast Laurasia.