摘要
关于古亚洲洋构造体制作用的最后时限和具体影响的空间范围一直存在争议。对采自内蒙古阿鲁科尔沁旗地区二叠系林西组砂岩的岩石磁学和古地磁学研究表明,样品的载磁矿物主要为磁铁矿,131块样品的磁化率各向异性(AMS)的最大主轴方向平行于层面方向,最小轴垂直于层面,显示了正常的沉积组构。对9个采点共131块样品进行逐步的系统热退磁实验,最终8个采点的72块样品获得了稳定的特征剩磁方向。E1校正检验表明,可能存在较明显的沉积倾角浅化现象,校正后的磁倾角为24.9°,相对的古纬度为13.1°N,校正后获得的古地磁极位置为56.7°N/318.7°E。说明晚二叠世该地区与华北板块已经结合为一个整体,为恢复晚古生代古亚洲洋在研究区的构造-沉积格架和发展过程提供了有力约束。
The closure time and spatial extent of the Palaeo-Asian Ocean remain topics of much controversy. Rock magnetic and palaeomagnetic studies of Permian sandstone from Taohaiyingzi area in Inner Mongolia indicate that the main magnetic mineral is magnetite. Anisotropy of magnetic susceptibility of 131 samples indicates that the directions of the principal axis K1 are parallel to the bedding planes and the minor axis K3 is perpendicular to them, which indicates a normal sedimentary fabric and confirms primary depositional nature of these sandstones. A total of 131 samples from 9 sites were subjected to thermal demagnetization. 72 samples from 8 sites yielded stable characteristic components. The overall average direction is D/I=349.8°/9.9°（A95=5.7°） and the corresponding palaeomagnetic pole is at 49.6°N and 316.0°E （A95=6.5°）. An elongation-inclination （E1） test indicates the existence of inclination shallowing. The corrected inclination is 24.9° and the corresponding palaeolafitude is 13.1°N. The palaeomagnefic pole after correction is 56.7°N and 318.7°E. From these results the authors infer that the study area was part of the North China Block in the late Permian, and this understanding provides a new framework for constraining the tectonic evolution of the Palaeo-Asian Ocean in the late Palaeozoic period.
出处
《地质通报》
CAS
CSCD
北大核心
2013年第2期388-398,共11页
Geological Bulletin of China
基金
中国地质调查局项目<古亚洲洋构造体制与滨太平洋构造体制叠加转变综合调查和研究>(编号:1212011085473)
<东北地区晚古生代以来构造演化特征综合研究>(编号:1212011121085)>
<兴蒙造山带基本构造格局综合调查和研究>(编号:1212011085476)
关键词
林西组
二叠系
古地磁
古亚洲洋
Linxi Formation
Pernfian
Palaeomagnetism
Palaeo-Asian Ocean
