磁组构的分离与岩石构造变形分析

The AMS (anisotropy of magnetic susceptibility) obtained under current experimental conditions is a comprehensive response to the superposition of the anisotropy of magnetic susceptibility of all magnetic minerals in the rock. The comprehensive analysis of detailed rock magnetism and structural geology shows that the results of conventional AMS tests usually cannot reveal the complex structural deformation process of the rock. This paper reviews the experimental methods such as anisotropy of anhysteretic remanent magnetization (AARM), low-temperature AMS (LT - AMS) and high-field AMS (HF - AMS) to separate the AMS components of the rock, which can quantitatively obtain the contribution of the magnetic fabric of different magnetic minerals and then explain their different deformation characteristics. On this basis, it expounds the theoretical and technical innovations and progress of the AMS separation methods for different magnetic mineral assemblages in recent years and their application prospects in the analysis of the structural deformation characteristics of rocks, discusses the rock magnetic properties of common single crystals of magnetic minerals and the complexity and limitations of the degree of anisotropy (P_j) and shape factor (T) in revealing the deformation characteristics of rocks, and finally gives examples and analyzes the application of the magnetic fabric separation technique in the analysis of the structural deformation of rocks in orogenic belts.

目前实验条件下获得的AMS(磁化率各向异性)是岩石内所有磁性矿物磁化率各向异性叠加的综合响应,详细的岩石磁学和构造地质学的综合分析表明常规AMS测试结果通常无法揭示岩石复杂的构造变形过程.本文综述了运用非磁滞剩磁各向异性(AARM)、低温AMS(LT-AMS)和高场AMS(HF-AMS)等实验方法对岩石AMS组分进行分离,可以定量获取不同磁性矿物的磁组构贡献,进而解释其不同的变形特征.在此基础上阐述了近年来针对不同磁性矿物组合的AMS分离方法的理论技术创新和进展及其在岩石构造变形特征分析中的应用前景,讨论了常见磁性矿物单晶的岩石磁学性质及各向异性度(P_j)与形状因子(T)在揭示岩石变形特征中的复杂性与局限性,最后举例并分析了磁组构分离技术在造山带岩石构造变形分析中的应用.