摘要
利用岩石磁化率量值椭球体与岩石构造应变椭球体的共轴性,在缺乏岩性标志层的高喜马拉雅结晶基底(聂拉木地区)进行岩石磁组构研究,进而研究喜马拉雅造山带的变形期次和过程.磁组构特征表明:磁化率各向异性度P在樟木镇北1km处的片岩最高为1.72,在康山桥南1km处最低,为1.13;百分率各向异性度H在11.82%～45.07%之间;磁性线理L在1.02～1.09之间,磁性面理F在1.06～1.60之间,磁性面理F比磁性线理L发育;磁化率椭球体的形状因子T在0.19～0.76之间,磁化率椭球的扁率E在1.04～1.49之间,磁化率椭球体的形状为一压扁椭球;樟木镇北1km到肉切村,平均最小磁化率主轴方向D3为S-N(除聂拉木北1km的MA9外),大多数样品最小磁化率主轴方向倾角I3>51°,最高达72.6°,局部发育有拉长形磁化率量值椭球体.本文研究结果表明,聂拉木地区早期经历强烈的韧性变形,推测可能是一条巨大的右旋逆冲韧性变形带,晚期构造掀斜.
Xizang in show that Zhangmu We give a detailed description of the magnetic fabrics of the rocks from the Nyalam region, southern order to fathom the deformational phases and processes in the Himalayan orogenic belt. The results the anisotropy （P） of magnetic susceptibility in the rocks is highest in the schist 1 km north of Town, with a maximum value of 1.72, while lowest in the rocks 1 km south of Kangshanqiao, with a minimum value of 1.13. The percentage anisotropies （H） of magnetic susceptibility range between 11.82% and 45.07%, indicating that the rocks in these places were once subjected to severe thrusting and plastic deformation during the early stages of the collision between the Indian plate and Eurasian plate. The Nyalam and Rouqiecun Group Complexes may be considered as a giant ductile shear zone. The magnetic lineations （L） vary between 1.02 and 1.09, and magnetic foliations （F） between 1.06 and 1.60. The magnetic lineations are apparently better developed than the magnetic foliations. The shape factors of magnetic ellipsoids （T） range between0.19 and 0.76, and the flattening （E） of the magnetic ellipsoids between 1.04 and 1.49. The magnetic ellipsoids tend to take the shape of a flaser ellipsoid. From the region 1 km north of Zhangmu Town to Rouqieeun, the main axis （D3 ） of mean minimum magnetic ellipsoids is oriented S-N （apart from the MA9 lkm north of Zhangmu Town）, and main axial dip angle （13） is greater than 51°, even up to 72.6°. The results of research have demonstrated that the combination of NS-directed compressional stress and NWW- trending structural plane resulted in the strike-slipping shear of dextral ductile oblique thrusting, rapid uplifting of mountain masses and high topographic reliefs on the Higher Himalayan crystalline basement. The locally developed elongated magnetic ellipsoids indicate that the combination of gravitational potential energy of the mountain masses and northward compressional force caused by the Indian plate led to nearly NS-trending extension and collapse and the formation of a dextral ductile shear zone similar to tilted structures.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2006年第2期496-503,共8页
Chinese Journal of Geophysics
基金
中国地质调查局1:25万聂拉木县幅区域地质调查项目(19911300009031)资助
关键词
磁组构
藏南拆离系
主中央断裂
聂拉木
Magnetic fabrics, South Tibet detachment system, Main central thrust, Nyalam
