川滇地块古新统宁蒗组磁组构特征及构造意义  

Magnetic fabric study of the Paleocene Ninglang Formation in the Chuandian Fragment and its tectonic implications

作　　者：高亮[1,2] 仝亚博[2,3] 王恒[2] 秦永鹏[2] 王艳[2] 汤怡[4] 杨振宇[1,2,3] 

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]国土资源部古地磁与古构造重建重点实验室,北京100081 [4]中国石油管道科技研究中心,河北廊坊065000

出　　处：《地球物理学报》2014年第1期199-213,共15页Chinese Journal of Geophysics

基　　金：中国地质调查局地质调查项目<川滇地块旋扭变形过程定量研究>(1212011120164);国家深部探测技术与实验研究专项(Sinoprobe08-01-01);中央级公益性科研院所基本科研业务费<青藏高原东南缘思茅地体旋转变形古地磁学研究>(DZXJK201207)共同资助

摘　　要：对川滇地块程海断裂附近的宁蒗地区古新统宁蒗组地层进行了详细的磁组构研究,沿战河-西布河布置了22个采点(钻取287块样品),综合分析表明研究区内存在四种磁组构类型,分别为初始变形磁组构和铅笔状磁组构以及介于上述两者之间的两种过渡型磁组构.研究区西侧(采点1—9)K1轴优势方向为近NNE-SSW方向,东侧(采点13—22)K1轴优势方向则为近S-N向,K1轴方向的突然变化可能与研究区内的隐伏断层活动有关.另外,磁组构也可以很好判断断层所夹持块体之间的相对旋转运动.将两组K1轴优势方向经过旋转校正之后,发现研究区内中-晚始新世时古应力方向为近E-W向,该应力方向主要与新生代印欧碰撞有关.此外,E-W向的古应力场明显不同于现今的近S-N向的应力场方向,这可能与印欧碰撞后青藏高原从前期的挤压缩短阶段进入到后期的E-W向伸展阶段有关.A detailed study of magnetic fabric was carried out on red beds of the Paleocene Ninglang Formation near the Chenghai fault in the Chuandian fragment. 287 oriented samples were collected from 22 sampling sites along the Zhan river and Xibu river. Comprehensive analysis shows 4 types of magnetic fabrics： initial deformation magnetic fabric, pencil-shapedmagnetic fabric and two types of transitional forms in between. The preferred orientation of K~ in the western part of the studying area （sampling site 1-9） was NNE-SSW, and changed to S-N in the east （sampling site 13-22）. The abrupt changes of K1 direction may be related to the existence of a blind fault. In addition, we find the magnetic fabric can make a fair judgment of the block rotations which are bonded by a series of faults. After correcting the local rotation, the study area was suffered from an E-W maximum principal compressional paleostress during the Middle-Late Eocene, which may be caused by the India and Eurasia collision. Moreover, the E-W paleostress is significantly different from present approximately S-N stress direction, which was related to the changed deformation types of the Tibetan plateau from the initial stage of compression to the later E-W extension.

关 键 词：磁组构 川滇地块 构造旋转 古应力 

分 类 号：P318[天文地球—固体地球物理学]