印支地块思茅地区始新统磁倾角偏低现象及其构造意义  

Eocene Paleomagnetic Inclination Shallowing in Simao Area of the Indochina Block and Its Tectonic Implication

作　　者：安纯志 杨振宇[3] 仝亚博[1,2] 李晨皓[1,2] 王恒[1,2] 高亮[1,2] 韩志锐[1,2] 徐颖超[1,2] 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]国土资源部古地磁与古构造重建重点实验室,北京100081 [3]首都师范大学资源环境与旅游学院,北京100048

出　　处：《吉林大学学报（地球科学版）》2017年第2期511-525,共15页Journal of Jilin University：Earth Science Edition

基　　金：中国地质调查局地质调查项目(1212011120164;12120114002301);国家自然科学基金项目(41202162)~~

摘　　要：对印支地块思茅地区始新世陆相红层进行古地磁研究,获得勐伴剖面特征剩磁方向为Ds=118.2°,Is=22.1°,k=31.6,α95=10.9°;勐腊剖面特征剩磁方向为Ds=47.6°,Is=22.8°,k=20.2,α95=5.9°。其特征剩磁方向与前人研究结果基本一致。利用Hodych等的磁倾角校正方法得到校正磁倾角为28.4°±4.3°,对前人的数据重新进行E/I统计得到的校正磁倾角值为30.7°,置信区间为[25.4°,35.9°],两种不同方法得到了较一致的结果,思茅地区的古近纪磁倾角显示了一定程度的偏低。E/I磁倾角偏低检验方法在应用时存在一定的局限性,变形微弱地层的古地磁学数据适合进行E/I磁倾角偏低校正,以避免倾伏褶皱或差异性旋转变形作用对E/I磁倾角偏低校正的影响。Hodych等提出的磁倾角校正方法是现今比较可靠的磁倾角校正方法。结合前人印支地块的古地磁研究成果,本次研究结果表明印支地块思茅地区自始新世以来相对于华南板块向南滑移量约500km。Paleomagnetic inclination shallowing studies were carried out on the Eocene red beds in Simao area of the Indochina block.High-temperature magnetic components were isolated from the Mengban and Mengla sections,the tilt corrected site-mean directions at Mengban and Mengla are Ds=118.2°,Is=22.1°,k=31.6,α95=10.9°,and Ds=47.6°,Is=22.8°,k=20.2,α95=5.9°,respectively,which are consistent with those previous research results in these areas.The inclination shallowing correction method proposed by Hodych Buchan and elongation/inclination（E/I）correction are used to quantitatively estimate the inclination bias of Eocene red-beds in the Mengban and Mengla area.The corrected inclinations are 28.4°±4.3°and 30.7°[25.4°,35.9°]following the method of Hodych Buchan and E/I correction,respectively.These results indicate that deposition and/or compaction induced inclination shallowing existed in the Paleogene red-beds in the southern part of Simao terrane.The usage of E/I correction is limited in the strata with weak deformation,in which the influence of plunging fold or local rotational deformation will strongly deviate the declinations.Hodych Buchan＇s method is more reliable for the inclination correction of red beds.Combining with previous paleomagnetic data from the Indochina block,these results presented in this paper indicate that the Indochina block has been subjected to southeastward displacement by 500 km with respect to the South China block since the Eocene.

关 键 词：印度支那地块 古近纪 地块运动 古地磁 磁倾角偏低 

分 类 号：P618.81[天文地球—矿床学]