• 责任者：Li Gang (College of Earth Sciences ; Jilin University ; Changchun 130061 ; China) ; Liu Zhenghong
• 刊名：Geological Bulletin of China
• 出版年：2013
• 卷期：32(2/3)
• 关键词：韧性剪切带 ; ductile shear zones ; 辽宁 ; Liaoning Province
• 页码：p.408-423
• 图表：illus., 3 tables, 57 refs.
• 分类号：0300
• issnNo：ISSN1671-2552
• isbnNo：CN11-4648/P

The Yiwultishan metamorphic core complex was formed by two stages of extension that occurred in Middle-Late Jurassic and Early Cretaceous respectively. Finite strain measurement shows that the Flinn exponent of the earlier extension （Middle-Late Jurassic） and the later extension（Early Cretaceous） are 0.50-6.06 （2.78 on average） and 0.21-2.39 （1.23 on average） respectively. The kinematic vorticity （Wk） estimated by Polar Mohr Circle diagram of earher extension is 0.00-0.82 （0.56 on average）, whereas the later extension＇s Wk is 0.5-0.93 （0.75 on average）. The Wk of the extensional crenulation cleavage （C＇） estimated by C＇ method ranges from 0.31 to 0.72. The analysis of finite strain and kinematic vorticity suggests that the two stages of extension in Yiwultishan area were asymmetrical, and the strain type of Middle-Late Jurassic deformation is pure dominated general shearing with elongation at earlier extension and plane strain at later extension. Plane strain with equally simple and pure shearing at earlier extension and pure dominated at later extension constitute the strain type of Early Cretaceous deformation. A comparison of the deformation conditions and paleo-stresses of two stages of extension indicates that the earlier extension is characterized by higher deformation temperature, lower differential stress and higher strain rate, whereas the later extension is characterized by lower temperature, higher differential stress and lower strain rate. All these characteristics, combined with the modes of occurrence and deformation features of syn-extensional dikes, plutons and their wall rocks, suggest that decompressed melting occurred in the middle and lower crust under an approximately horizontal extension in Yiwulushan area in Middle-Late Jurassic period; after a short compression at the end of Late Jurassic, the area underwent an approximately hori- zontal extension in early Early Cretaceous and then the deformation turned into perpendicular uplift, and finally led to the formation of metamorphic core complex.