内蒙大青山早前寒武纪造山带部分熔融岩石流变行为研究

The lithosphere of continent is different from that of ocean, which is characterized by complicated rheology. Recently, the study on rheological behavior of continental lithosphere has become an international geodynamic research frontier for understanding the deformation and evolution of lithosphere. This project plans to carry out detail rock rheological research on the early Precambrian high-grade metamorphic complexes from different tectonic level with different partial melting in Daqingshan area, Inner Mongolia. The studies will be focused on the relationships between the rock types, partial melting and rheological features to reveal the relation between partial melting and rock rheology, the process of partial melting and later its structural response. The control factors of rock rheological behavior under partial melting setting and the rock rheological roles and mechanics under solid-liquid two facies condition will be studied. Finally, the evolution model of the continental orogen will be established for the partial melting crustal environment.

大陆岩石圈与大洋岩石圈不同，具有复杂的流变学特性。目前对大陆岩石圈流变行为的研究已成为解读认识岩石圈变形和演化的地球动力学研究国际前沿。本项目以内蒙古大青山-乌拉山地区广泛出露的不同构造层次和不同熔融程度的前寒武纪高级变质杂岩为重点解剖对象，开展岩石类型、熔融程度和流变特征之间的空间结构关系研究，重点查明变质-熔融作用与构造流变作用的时空对应关系、部分熔融过程及后续构造效应。探讨部分熔融条件下岩石流变行为的控制因素，总结部分熔融固-液两相介质条件下岩石的流变规律和机制，建立与部分熔融地壳环境相适应的大陆造山带演化模型。

查明研究区变形特征及构造要素叠加关系；总结了区域上不同构造层次变形样式和流变特征；建立了造山带深熔下地壳早期发育近水平和晚期陡倾流变带的构造模型；总结了不同深熔程度下斜长石变形机制；查明混合岩形成的深融机制及其多期熔融特点；详细揭示了深熔混合岩在熔融前、熔融中和熔融后不同阶段的流变行为及其地震波属性；大青山古元古造山带深熔地壳岩石的变形机制主要受位错蠕变，扩散蠕变和颗粒流动来调节。随着地壳的加厚，岩石变质深熔程度逐渐增加，变质深熔岩中固-液相的比例控制了下地壳的流变样式，据此，初步建立了大青山地区深熔地壳的流变结构模型。