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摘要
Tangzang-Guanzizhen-Wushan and Xinyang-Yuanlong tectonic zones are the major suture zones in Joint area of Qinling and Qilianshan mountains. Structure analysis and the anisotropy of low-field magnetic susceptibility (AMS) of 168 samples from 41 sites was measured to determine the strain and fabric of the high strain shear zone in the suture zones. Most of the mean susceptibilities (K(m)) are low. Magnetic ellipsoid analysis displays that most of the samples are dominated by shear and oblate compressional fabric, and have high values of anisotropy magnitude which increases with the intensity of deformation. Caution should be exercised when use T and P' to deduce the shape of magnetic ellipsoid and the deformation intensity for they are also affected by rock types. The directions of principle susceptibilities are closely related to deformation, the magnetic foliations defined by K(max) and K(int) are divided into two conjugate groups that imply the gridding configuration of high strain shear zone; clustered foliation and more scattered lineation are attributed to the shearing and flattening regime. Most of the samples have steep magnetic foliations and subhorizontal magnetic lineations and others have steep lineation, which demonstrate the transpressional characteristics of the shear zone. And shear sense of complex high strain zone inferred from magnetic fabric may be unreliable or even wrong for variation of the foliation attitude across the shear zone and great angle between K(min) and the striking of shear zone.
- 出版日期2009-1
- 单位西北大学; 中国科学院地质与地球物理研究所兰州油气资源研究中心; 长安大学; 中国科学院地质与地球物理研究所
