Geometry and Kinematics of the Xianshuihe Fault Belt in Southwestern Sichuan, Eastern Tibetan Plateau: Constraints from Magnetic Fabrics
详细信息
- 责任者：Chen Yingtao (State Key Laboratory of Continental Dynamics ; Department of Geology ; Northwest University ; Xi’an 710069 ; China) ; Zhang Guowei
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(3)
- 关键词：磁性组构 ; magnetic fabric ; 断裂带 ; fracture zones ; 鲜水河断裂带 ; Xianshuihe Fault Zone
- 页码：p.977-989
- 图表：illus., 1 table, 51 refs.
- 分类号：0300
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
In order to probe into the geometry and kinematics of the Xianshuihe fault belt,this paper carried out a structural deformation characteristics research to the Xianshuihe fault belt through the anisotropy of magnetic susceptibility(AMS) and thermomagnetic analyses of 296 oriented samples on the basis of the field structural,and microstructural analyses.Average susceptibility(km) values of the collected samples are generally small so that they are slightly weak magnetic to weak magnetic.Thermomagnetic curves and microstructure demonstrate that paramagnetic minerals such as biotite might be the dominant contributions to the susceptibility of the mylonite ones.Anisotropy degrees of the magnetic susceptibility(PJ) are relatively large indicative of a strong structural deformation of the Xianshuihe fault belt.Shape parameter(T) are generally more than zero and the flattening(E) distribute around 1,indicating that the susceptibility ellipsoid of the Xianshuihe fault belt is mainly oblate.Compared to the magnetic lineations,magnetic foliations are relatively developed,demonstrating that the main deformation styles of the Xianshuihe fault belt are shear and flatten with stretch.This further indicates that the Xianshuihe fault belt has comprehensive features of multiple structural deformations.Orientation of minimum susceptibility principal axis(Kmin) showed that the northern and southern section of Xianshuihe fault belt were controlled by nearly EW and NE-SW compressive stress.On the other hand,the Kmin orientation and its plunge angle characteristics showed that the Xianshuihe fault belt was mainly characterized by left-lateral strike-slip shear and the blocks on either side of the northern section had a certain relative uplift respectively in two different tectonic movement stages although lifting amplitude were small.In the southern section,SW block lifted,compared with the NE side.The whole characteristics of Xianshuihe fault showed that it is evolving southward gradually transforming into a compressive tectonic.It might be related to the tectonic setting what eastward escape of materials of the Tibetan Plateau and connection of Xianshuihe fault with Longmenshan fault belt.
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