再论“大陆深俯冲和折返动力学”:来自中国大陆科学群钻及苏鲁超高变质带的制约

Continental deep subduction and exhumation dynamics:Constraints from holes of the Chinese Continental Scientific Drilling and the Sulu HP-UHP metamorphic terrane.

通过CCSD-MH、卫星孔的岩性-构造剖面和苏鲁造山带中榴辉岩-超镁铁质岩的产出、深俯冲/折返过程的岩石的塑性流变特征和变形序次的分析、俯冲-折返过程中流体作用及变质化学地球动力学对流变学行为的制约,以及韧性剪切作用形成的折返年代学时限,提出苏鲁超高压变质地体为面型深俯冲/折返杂岩带组成的穹形挤出推覆岩片、叠置在扬子陆块之上;根据岩石变形微构造及组构的分析,重塑超高压变质岩石深俯冲阶段、折返早期、折返主期和折返后期的塑性流变;提出深俯冲的物质沿板块汇聚边界的多层隧道呈多重/分片样式"挤出"的折返模式,并认为在折返初期开始(230～220Ma)和折返主期(220～200Ma)形成的透入性韧性剪切是俯冲岩片挤出的重要机制;提出郯庐走滑断裂的形成对苏鲁高压/超高压变质地体演化的影响。

Detailed reconstruction for plastic deformed, ductile shearing, fluids reaction and metamorphic geochemistry during subduction and exhumation of ultrahigh-pressure (UHP) rocks from petro-tectonic profiles of the main hole and satellites of the Chinese Continental Scientific Drilling (CCSD-MH) and the Sulu metamorphic terrane have provided new important constraints for the deep subduction and exhumation dynamics of continents. It is proposed that the Sulu UHP metamorphic terrain is composed of flat subduction-exhumation complex belts which overlap on the Yangtze Block as superimposed slices. Based on the plastic deformation features of eclogites and garnet peridotites during the whole exhumation, the penetrative ductile shear zones formed at the early stage (230 similar to 220Ma) and enhanced at the main stage (220 similar to 200Ma) are thought be the important extrusion mechanism of subduction slices. Futhermore, it is suggested that TanLu strike slip fault has played an important role on the evolution of the Sulu high/ultrahigh-pressure metamorphic terrain.