印支地块中生代构造演化的古地磁制约研究  

Paleomagnetic study on the Mesozoic tectonic evolution of the Indochina Block

作　　者：贾舒斐 黄宝春[1] 闫永刚 赵千 李能韬 JIA ShuFei;HUANG BaoChun;YAN YongGang;ZHAO Qian;LI NengTao(Key Laboratory of Orogenic Belts and Crustal Evolution,Ministry of Education,School of Earth and Space Sciences,Peking University,Beijing 100871,China;Guangdong Provincial Key Laboratory of Geodynamics and Geohazards,School of Earth Sciences and Engineering,Sun Yat-sen University,Zhuhai Guangdong 519000,China;National Park Research Center,School of Economics and Management,Sanming University,Sanming Fujian 365004,China)

机构地区：[1]北京大学地球与空间科学学院,造山带与地壳演化教育部重点实验室,北京100871 [2]中山大学地球科学与工程学院,广东省地球动力作用与地质灾害重点实验室,广东珠海519000 [3]三明学院经济与管理学院,国家公园研究中心,福建三明365004

出　　处：《地球物理学报》2022年第9期3481-3501,共21页Chinese Journal of Geophysics

基　　金：国家自然科学基金(92055205,41774074)资助。

摘　　要：本文报道泰国西北部Nakhon Thai盆地中生代Nam Phong组、Phu Kradung组、Phra Wihan组和Sao Khua组的古地磁学和碎屑锆石U-Pb年代学研究结果,以期为印支地块中生代构造演化提供新的古地磁学约束.碎屑锆石U-Pb年代学测试获得了Nam Phong组、Phu Kradung组和Sao Khua组对应的最大可能沉积年龄分别为约208、约154和约140 Ma;指示Phra Wihan及其上的Sao Khua组为早白垩世沉积.同时,这三个组的碎屑锆石年龄谱进一步证实了印支地块在中-晚侏罗世发生了一次沉积物源的转换.古地磁学研究获得3个古地磁极:晚三叠世Nam Phong组为55.9°N/172.2°E(A_(95)=4.6°)、晚侏罗世Phu Kradung组为61.0°N/182.3°E(A_(95)=6.2°)和早白垩世Phra Wihan组为67.0°N/192.1°E(A_(95)=3.6°).其中,前两个古地磁结果通过了褶皱检验,且具有很好的区域一致性,表明其很可能为岩石形成时获得的原生剩磁,对应古地磁极可作为印支地块中生代的关键古地磁极.结合已有数据,新建立的印支地块中生代视极移曲线表明,印支地块晚三叠世以来的约1200~1400 km的显著南移主要发生在中生代;但是,尽管新生代以来的印度与亚洲大陆的碰撞与持续挤压可能是印支地块晚三叠世以来发生水平旋转的的主因,但侏罗-白垩纪期间印支地块的显著南移同样伴随着一定量(18.8°±7.8°)的顺时针水平旋转.We report a combined paleomagnetic and U-Pb geochronologic study on sedimentary rocks from the Nam Phong,Phu Kradung,Phra Wihan and Sao Khua formations in the Nakhon Thai Basin,NW Thailand in order to provide independent constraints on the tectonic movement of the Indochina Block during the Mesozoic era.The detrital zircon U-Pb geochronologic analyses indicate the maximum allowable depositional age of the three formations to be~208,~154 and~140 Ma,respectively.This constrains that the Phra Wihan Formation as well as the overlying Sao Khua Formation should have a deposition age of the Early Cretaceous.Our detrital zircon U-Pb age spectra for the three formations further ascertain the view that the Indochina Block experienced a sediment provenance transition during the Middle to Late Jurassic times.Combined with previous reliable paleomagnetic data from the Khorat Basin of Indochina,paleomagnetic analyses on the three sampling formations from the Nakhon Thai Basin yield three paleomagnetic poles,at 55.9°N/172.2°E(A_(95)=4.6°)for Late Triassic Nam Phong Formation,61.0°N/182.3°E(A_(95)=6.3°)for Late Jurassic Phu Kradung Formation,and 67.0°N/192.1°E(A_(95)=3.6°)for Early Cretaceous Phra Wihan Formation,respectively.The site-mean directions of the characteristic remanence for the former two paleopoles passed the fold test at 95%confidence level and show a well regional consistency between the Khorat and Nakhon Thai basins,suggesting that they are very likely primary remanences,and consequently their corresponding paleomagnetic poles could be used as key poles for the construction of Mesozoic apparent polar wander path(APWP)for the Indochina Block.Thus,we construct a new Mesozoic APWP for the Indochina Block in the light of our new paleomagnetic results from the Nakhon Thai Basin of NW Thailand and reliable Mesozoic paleomagnetic results from the Khorat Basin in central Indochina.The new Mesozoic APWP of Indochina indicates that the significant southward movement of~1200-1400 km since the Late Triassic of the I

关 键 词：印支地块 中生代 构造古地磁 碎屑锆石年代学 构造演化 

分 类 号：P318[天文地球—固体地球物理学]