桐柏—大别—苏鲁UHP和HP变质带的结构及流变学演化  

Structure and Rheological Evolution of UHP and HP Metamorphic Belts in the Tongbai-Dabie-Sulu Region, China

作　　者：索书田[1] 钟增球[2] 韦必则[2] 张宏飞[2] 周汉文[2] 游振东[2] 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地球科学（中国地质大学学报）》2002年第5期548-557,共10页Earth Science-Journal of China University of Geosciences

基　　金：国家重点基础项目 (No .G19990 7550 6 );国家自然科学基金项目 (No .4 9972 0 6 7;4 9794 0 4 1)

摘　　要：在岩石圈流变学基本原理指导下 ,运用现代构造解析学方法 ,在不同尺度上判别和分析了桐柏—大别—苏鲁UHP和HP变质带内深俯冲、同碰撞构造及UHP和HP岩石折返过程中的变形特征 ,重点讨论同碰撞形成的高角度网结状榴辉岩相剪切带阵列、高角闪岩相剪切及有关变形组合以及碰撞期后伸展韧性薄化变形样式 ,强调指出不同地壳层次和物理条件下变形分解作用的重要性 ,而且 ,在UHP和HP变质带内最有效的应变体制是剪切作用 ,并在三维空间上形成不同格式的剪切带网状系统 .以构造学记录为主线 ,结合已有可利用的岩石学、变质作用 pT轨迹和同位素年代学资料 ,提出一个UHP和HP变质带尺度上的流变学演化模式 ,其中 ,UHP和HP变质岩石由地幔深度折返到地壳表层 ,经历了楔状挤出、碰撞期后地壳韧性薄化及晚造山伸展塌陷。The basic principles of lithospheric rheology and the modern analytical tectonics are used to examine deformational features of the rocks and the processes responsible for their formation and exhumation in the UHP and HP metamorphic belts within the Tongbai Dabie Sulu region, China. The discussion is concentrated on high angle, anastomosing shear zone arrays which were formed under UHP eclogite facies conditions, and related to the Triassic (250-220 Ma) collision between the Sino Korean and Yangtze cratons, and shear zone assemblages accompanied, following the collision, by decompressional partial melting, formed by a compressional regime on upper amphibolite facies conditions, as well as deformation pictures formed by ductile extension flow and thinning on amphibolite facies conditions, mostly between 200 Ma and 170 Ma. It is suggested that the deformation partitioning plays an important role in the deformational processes for the rocks within the UHP and HP belts, at different crustal levels and on different physical conditions. The efficient strain regime in the UHP and HP metamorphic belts is shear, which is generally localized in networks of ductile shear zones on all scales. On the basis of structural records mainly and combined with the previous data on petrography, pT paths of UHP metamorphic rocks and geochronology, a speculative rheological evolution model for the UHP and HP metamorphic belts is proposed. In this model, 250 to 220 Ma is considered as the most reliable estimated age for the occurrences of both the UHP and HP metamorphism and the continental collision between the Sino Korean and Yangtze cratons. The major consequence of this collision was the development of a crustal stacking wedge. The UHP and HP metamorphic rocks were exhumed from the mantle depth to the surface during a multistage history ,including wedge intrusion (220-200 Ma), crustal ductile thinning and extension flow (200-170 Ma) and late orogenic collapse and unroofing.

关 键 词：桐柏-大别-苏鲁区 HP变质带 岩石圈流变学 剪切带 韧性薄化作用 变形分解作用 UHP变质带 

分 类 号：P588.3[天文地球—岩石学] P542[天文地球—地质学]