摘要
对哀牢山 红河断裂带中段和平 水塘剖面、墨江 元江剖面和其它地段的岩石应变及磁组构进行了分析 ,表明应变强度的校正磁各向异性度PJ从断裂带向西至三叠系明显降低 ,变形强度向西迅速减弱。磁化率椭球体主轴展布反映出剪切带内、外变形方式的改变。剪切带内 ,以水平走滑运动为主 ;向西则以水平缩短为主。在应变分析中 ,对断裂带内的S C组构两组面理夹角、杏仁体和石榴石应变标志体进行了测量 ,结果显示 ,剪切带内的磁组构和岩石组构间关系较差。此外 ,还对这两条剖面中的三叠系进行了应变和磁组构分析 ,找出了它们与磁化率椭球体对应轴率间的相关性。
Heping-Shuitang and Mojiang-Yuanjiang sections along with other sample sites along Ailao Shan-Red River shear zone were systematically surveyed to investigate strain and magnetic fabrics. The value of site mean corrected anisotropy degree parameter P J decreases obviously from the shear zone westward to the Triassic sediments. In Heping-Shuitang section, it drops by 22.4% in the low-grade schist and by 27.4% in the Triassic sediment on average with respect to the gneiss. In Mojiang-Yuanjiang section, P J drops by 12.6% (MY25 not included) and 21.2% westward on average with respect to the core gneiss, indicating a rapid decrease of deformation intensity. Magnetic fabric is closely associated with the Red River strike-slip faulting. In the shear zone the magnetic lineation K max axes are parallel to the lineation, and the overall minimum magnetic axes align NE-SW with sub-horizontal to low dip angles. In the Triassic mudstone to the west, the maximum and minimum axes tend to group towards east-west, parallel to down-dip of cleavage. This indicates changes in deformation mechanism inside and outside the shear zone. Within the shear zone, horizontal movement is dominant; whereas EW shortening is important outside the zone. The finite strain along Ailao Shan-Red River shear zone has been studied through analysis of strain markers and S-C fabrics. The ellipticity R xz of chloritic amygdule in the Permian basalt ranges from 6.79 to 10.47, and the ellipticity R xz of garnet from 1.56 to 2.95 in the core gneiss. The S-C angle of the sheared rocks varies from 6 to 34 , and most of them lie in a range of 10° to 30°. The corresponding average shear strains are 3.36 (γ sc) for S-C fabric, 2.43 (γ xz) for amygdule, and 0.72 (γ xz) for garnet. Comparison between strain and magnetic fabrics of mylonites shows no relationship in the core gneiss. Additionally, the reduction spots in the Triassic have been studied. The site mean X/Y ratios of reduction spots vary from 1.149 to 3.527, and the X/Z ratios from 1.724 to 7.903. Two tentative quantitative relationships between the magnetic and strain ellipsoids have been made for their natural logarithmic maximum to intermediate and maximum to minimum axial ratios.ln(X/Y) = 13.80lnL+ 0.548 ln(X/Z) = 4.45lnP+ 1.156
出处
《热带海洋学报》
CAS
CSCD
北大核心
2003年第2期17-29,共13页
Journal of Tropical Oceanography
基金
中国科学院知识创新工程项目 (KZCX2 2 0 9 0 5)
国家自然科学基金资助项目 (4 990 2 0 19)
