| 大别—苏鲁区UHP变质岩构造学及流变学演化 |
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| 引用本文： | 索书田,钟增球,周汉文,游振东.大别—苏鲁区UHP变质岩构造学及流变学演化[J].地学前缘,2008,15(3):150-167. |
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| 作者姓名： | 索书田 钟增球 周汉文 游振东 |
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| 作者单位： | 1. 中国地质大学(北京)地球科学与资源学院,北京,100083;中国地质大学(武汉)地球科学学院,湖北,武汉,430074
2. 中国地质大学(武汉)地球科学学院,湖北,武汉,430074 |
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| 基金项目： | 国家重点基础研究发展计划(973计划)
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国家自然科学基金 |
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| 摘 要： | 在大别—苏鲁区的30个关键位置,对UHP/HP变质岩进行详细构造解析、大比例尺(1∶10000)制图并在区域尺度上进行观察和对比,以便揭示它们的构造几何学、变形条件和流变学演化。初步的研究结果指出,广泛出露的UHP/HP榴辉岩相岩石形成一个巨大的UHP/HP变质带,提供了一个观察中朝与扬子克拉通之间三叠纪大陆深俯冲-碰撞带过程的窗口。观察的显微构造及组构指出,UHP/HP变质带内岩石变形机制,无论是在榴辉岩相阶段还是在榴辉岩相后阶段,都是以塑性流变为主,其力学行为和组构特征都受组成矿物的强度、强度差等流变学特征,以及变形物理环境如压力、温度、应变速率、差异应力和流体含量等的制约。在俯冲/碰撞带内的变形分解作用于岩石圈不同层次及不同的构造阶段都曾发生,而且,在不同尺度上,应变局部化形成具高应变的剪切带网络,且一般显示典型的布丁-基质或碎斑-基质构造及流变学型式。根据构造、岩石、变质作用及地质年代学资料,借助于岩石圈流变学基本原理,提出一个大别—苏鲁区UHP/HP变质岩石流变学演化的工作模式,它涉及早期扬子与中朝克拉通间三叠纪(~250~230Ma)大陆深俯冲/碰撞、UHP/HP变质岩形成,相继深埋岩石的多期折返。特别强调UHP/HP岩石向地壳表层的折返,主要是构造过程,地面侵蚀作用是次要的。
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| 关 键 词： | 大别—苏鲁区 榴辉岩 超高压(UHP) 岩石圈流变学 强度差 变形分解作用 俯冲 折返 |
| 文章编号： | 1005-2321(2008)03-0150-18 |
| 修稿时间： | 2007年8月10日 |
Tectonic and rheological evolution of UHP metamorphic rocks in the Dabie-Sulu region, eastern China. |
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| Suo Shutian,Zhong Zengqiu,Zhou Hanwen,You Zhendong.Tectonic and rheological evolution of UHP metamorphic rocks in the Dabie-Sulu region, eastern China.[J].Earth Science Frontiers,2008,15(3):150-167. |
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| Authors: | Suo Shutian Zhong Zengqiu Zhou Hanwen You Zhendong |
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| Abstract: | Detailed structural analysis and mapping at a scale of 1∶10 000 at more than 30 key locations in combination with extensive regional field observations of UHP/HP metamorphic rocks in the Dabie-Sulu region, eastern China were carried out in order to reveal their structural geometry, deformation conditions and rheological evolution. Preliminary results show that the well-exposed relict UHP/HP eclogite-facies rocks, outlining a giant UHP/HP metamorphic belt in eastern China, provide a window into Triassic continental subduction/collision-belt processes between the Yangtze craton in the south and the Sino-Korean craton in the north. The observed microstructures and fabrics clearly indicate that the deformation mechanism operating in the rocks, within the UHP/HP metamorphic belt, was dominated by plastic flow during both the UHP/HP eclogite- and post-eclogite-facies deformation histories. The mechanical behavior and deformation features of the rocks were strongly governed by the rheological properties, such as the strength and strength contrast of the constituent phases, as well as physical conditions of the deformation including pressure, temperature, strain rate, differential stress, fluid content, etc. Deformation partitioning within the subduction/collision belt occurred at different lithospheric levels (depths) and at different stages. Furthermore, strain, at various scales, was localized into heterogeneous networks of ductile shear zones of high strain, generally exhibiting a typical boudin-matrix or clast-matrix structural and rheological pattern. Based on structural, petrological, metamorphic and geochronological information and by means of the basic principles of the rheology of the lithosphere, we propose a revised rheological evolutionary scenario for the UHP/HP metamorphic rocks in the Dabie-Sulu region. The working model involves an early (250-230 Ma) continental crust subduction/collision between the Yangtze and Sino-Korean cratons, producing UHP/HP metamorphic rocks, and the subsequent polyphase exhumation of the deeply buried crustal rocks. Especially it is emphasized that the exhumation of the UHP/HP metamorphic rocks to the surface should be mainly attributed to tectonic processes, whereas surface erosion was subordinate. |
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| Keywords: | Dabie-Sulu region eclogite ultrahigh-pressure (UHP) rheology of the lithosphere strength contrast deformation partitioning subduction exhumation |
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