印支地块思茅地区早白垩世古地磁结果及其构造意义  

Early Cretaceous Paleomagnetic Results of the Simao Area in the Indochina Block and Its Tectonic Implications

作　　者：张海峰[1] 仝亚博[2,3] 王恒[2,3] 杨振宇[1,3] 

机构地区：[1]南京大学地球科学与工程学院,南京210093 [2]中国地质科学院地质力学研究所,北京100081 [3]中国地质科学院古地磁重点实验室,北京100081

出　　处：《地质学报》2012年第6期923-939,共17页Acta Geologica Sinica

基　　金：国家深部探测实验研究专项(编号Sinoprobe08-01-01);地质调查项目(编号1212011120164)资助的成果

摘　　要：对印支地块思茅地区的早白垩世红层开展详细的岩石磁学和古地磁学研究,获得镇沅剖面特征剩磁方向Ds=52.4°,Is=45.5°,κ=77.9,α95=6.3°;普洱剖面特征剩磁方向Ds=46.2°,Is=46.6°,κ=50.9,α95=5.6°;江城剖面特征剩磁方向Ds=8.6°,Is=42.2°,κ=117.1,α95=4.0°。对普洱和江城剖面进行E-I磁倾角偏低检验,结果显示江城剖面不存在磁倾角偏低,普洱剖面由于偏角较分散,导致其伸展方向出现假象,推测的磁倾角偏大,出现实测磁倾角偏低的假象。思茅地区各采样剖面之间的磁偏角差异表明,块体内部发生过差异性旋转变形,其变形的过程不仅受控于边界深大断裂,也与内部小断裂的活动有密切关系。若进一步考虑华南地块白垩纪可能存在的磁倾角偏低现象,则该结果说明印度支那地块思茅地区白垩纪以来相对于华南地块向南滑移量为570±310km,接近构造地质研究推测的红河大断裂左行滑移量。Rock magnetic and paleomagnetic studies were carried out on the Early Cretaceous red beds at Simao area of Indochina Block.The characteristic remanent magtization（ChRM） directions obtained for Zhenyuan,Pu’er and Jiangcheng are Ds=52.4°,Is=45.5°,κ= 77.9,α95=6.3°;Ds=46.2°,Is=46.6°,κ= 50.9,α95=5.6°;and Ds=8.6°,Is=42.2°,κ= 117.1,α95=4.0°,respectively.The elongation/inclination（E/I） correction model was applied to evaluate the inclination error of the Pu’er and Jiangcheng sections.The results indicate that inclination shallowing is negligible in Jiangcheng section.However,more discrete declination in Pu’er results in an illusion of elongation,and this is attributed to a large corrected inclination.The differences of declination between all the sample sections at the Simao area suggest that differential rotation has taken place within the block,with the deformation process not only controlled by boundary faults but closely related with activities of the internal small faults.Taken the Cretaceous shallow inclination in the South China block into consideration,the Simao area has been subjected to south displacement by 570±310km with respect to the South China block since Cretaceous,presumably close to the estimation of structural geology evidences.

关 键 词：印度支那地块 白垩纪 地块运动 陆内变形 

分 类 号：P534.53[天文地球—古生物学与地层学]