东昆仑造山带海西—印支期构造古地理演化的古地磁证据

PALEOMAGNETIC EVIDENCE FOR HERCYNIAN-INDOSINIAN TECTONOPALEOGEOGRAPHICAL EVOLUTION IN EASTERN KUNLUN OROGENIC ZONE

东昆仑造山带从北向南依次可划分出东昆北带、东昆中混杂岩带、东昆南带、阿尼玛卿混杂岩带和巴颜喀拉带５个大地构造地层带．根据对各地层带物质建造序列和构造古地理的研究基础之上所进行的古地磁分析认为，东昆北、东昆南、阿尼玛卿３个构造单元，在海西—印支期均处于北纬１４°～２０°之间．迄今为止，三者由南而北已漂移了约１５００～２０００ｋｍ．３个构造单元在不同时期的古纬度及古纬度差反映了多岛洋盆扩张和闭合的多旋回性．从东昆中到巴颜喀拉带，其洋盆的开裂、收缩、关闭和前陆盆地的演化更替，无论在时间上和地理位置上均呈现规律性的从北向南依次迁移的特点，即在时间和平面上构成定向性构造迁移和多旋回．

The Eastern Kunlun orogenic zone during Hercynian-Indosinian can be divided into five geotectonic stratigraphic subzones from the north to the south: the northern subzone of the Eastern Kunlun orogenic zone, the central melange subzone of the Eastern Kunlun orogenic zone, the southern subzone of the Eastern Kunlun orogenic zone, the Animaqing melange subzone, and the Bayankala subzone. The paleomagnetic analysis on the basis of the research into the material building sequence in each stratigraphic layer and into the tectonopaleogeography shows that the three structural units of the northern subzone of the Eastern Kunlun orogenic zone, the southern subzone of the Eastern Kunlun orogenic zone, and the Animaqing melange subzone were all located between latitudes 140°～200°N during the Hercynian-Indosinian. Up to the present, these three structural units have drifted from the south to the north by about 1500～2000km. The paleolatitudes in different periods and the differences between them for these three structural units indicate the polycycle of spreading and closing of the archipelagic oceanic basin. From the central melange subzone of the eastern orogenic zone to the Bayankala subzone, the opening, shrinkage, and closing of the oceanic basin and the evolutionary change of the foreland basin were characterized by the regular migration from the north to the south either in time or in geographical location, in other words, by the directional structural migration and polycycle both in time and in space.