喜马拉雅山北坡奥陶纪—古近纪构造古地磁新数据  

New Ordovician-Paleogene tectonomagnetic data from the northern slope of the Himalayas.

作　　者：朱同兴[1] 庄忠海[1] 周铭魁[1] 潘忠习[1] 冯心涛[1] 

机构地区：[1]中国地质调查局成都地质矿产研究所,四川成都610082

出　　处：《地质通报》2006年第1期76-82,共7页Geological Bulletin of China

基　　金：中国地质调查局1:25万聂拉木县幅(H45C004002)地质调查项目;国家自然科学基金项目(编号:40272012)成果。

摘　　要：在喜马拉雅山北坡奥陶系—古近系近乎连续的沉积地层中系统采集古地磁样品3791件,其中测试统计样品数为2920件,基本获取了统级年代古地磁数据,绘制出喜马拉雅地块奥陶纪—古近纪古地磁极移曲线和古纬度变化曲线。喜马拉雅地块在向北漂移过程中曾发生了多次旋转,最后一次约28°的顺时针旋转发生在始新世,可能与西喜马拉雅构造结形成有关;晚三叠世和晚侏罗世曾发生了纬度为2°和3.8°的向南回返,可能与雅鲁藏布新特提斯洋弧后扩张有关。根据古纬度数据推算:中白垩世雅鲁藏布新特提斯洋盆的宽度至少为2200km;始新世以来的喜马拉雅陆-陆碰撞造山运动导致印度地块-喜马拉雅褶冲带-拉萨地块之间的地壳缩短量至少为1000km。A total of 3791 systematic oriented paleomagnetic samples were collected from the Ordovician -Paleogene nearly consecutive sedimentary rocks on the northern slope of the Himalayas, southern Tibet, of which 2920 samples were analyzed and took part in the statistics. New magnetostratigraphic data of the series-rank were obtained and the Ordovician-Paleogene paleomagnetic apparent polar wander path and paleo-latitude curve of the Himalayan block were drawn. The paleomagnetic records suggest that the Himalayan block rotated several times during its northward drifting and that the final -28° clockwise rotation took place in the Eocene, which is probably related to the formation of the western tectonic syntax. South-directed inversions of 2° and 3.8° in latitude were recorded during the Late Triassic and Late Jurassic, which is likely to be related to the back-arc spreading of the Yarlung Zangbo Neo-Tethys Ocean. Based on the estimation of the paleo-latitude data, the Middle Cretaceous Yarlung Zangbo Neo-Tethys oceanic basin was at least 2200 km wide, and there was a crustal shortening amount of at least 1000 km between the Indian plate, Himalayan fold-thrust belt and Lhasa block resulting from the Himalayan continent-continent collisional orog, eny since the Eocene.

关 键 词：构造古地磁 奥陶纪—古近纪 喜马拉雅山北坡 

分 类 号：P54[天文地球—构造地质学] P318.44[天文地球—地质学]