阿尔金断裂带西段磁组构特征及其构造意义

变形岩石的磁组构参数K_max、K_int、K_min、P、T、F、L、E等可以用来定量地表征构造变形的形状及期次.本文通过对阿尔金断裂带（郭扎错—空喀山口段）中岩石磁组构特征分析，认为该断裂带具多期活动性，变形性状由早到晚依次表现为韧性、韧-脆性及脆性变形，应力机制为剪切以及带有剪切性质的拉伸和压扁，主应力方向为NNE-SSW和近SN向.磁组构特征还表明该断裂带两侧断块相对差异运动在不同地区有所不同，而且它们所经历的构造期次以及各期活动的应力机制、影响程度也有明显区别.此外，磁组构数据显示阿尔金断裂带具有中间变形强、向两侧变形逐渐减弱的准对称特点，其早期变形具有由东往西逐渐减弱的变化规律.由磁组构揭示的应力应变特征与野外露头、显微构造和古应力测量结果一致.

Characteristics of magnetic fabrics in western segment of the Altun fault belt and its tectonic significance

The parameters of magnetic fabric of deformed rocks such as Kmax,Kint,Kmin,P,T,F,L and E can be used to quantitatively display the behaviors and stages of tectonic deformation.Characteristics of magnetic fabrics in west segment of the Altun fault belt(from Guozhacuo to Kongkashankou)were analyzed in this investigation.These characteristics suggest that the segment had undergone multiple stages of mobility,and the deformation feature had experienced a successive transformation from ductile,to ductile-brittle and to brittle deformation.Stress mechanisms are indicative of shear,stretch and compress with shear.The direction of principal stress is NNE-SSW and approximately S-N.The fabric characteristics of the minimum magnetic susceptibility axis(Kmin)are different between the two blocks on the two sides of the strike-slip fault,and in different areas they have different movement vectors.Sinistral strike slip is proved to be the main movement form of the structure of the Altun fault belt.Magnetic fabric data also indicate that the Altun fault belt has the character of semi-symmetry with the most intensive degree of deformation in the middle,and a gradual decreasing towards both sides,showing that the deformation during the early period gradually decreased from east to west along the strike-slip fault belt.The stress,strain and the character of deformation revealed by magnetic fabrics are consistent with field features,microstructure and paleostress data.