花岗岩构造研究及花岗岩构造动力学刍议

花岗岩可以视为一种很好的构造标志体,犹如褶皱、断裂一样。从花岗岩浆的形成、融体分离、岩浆上升到岩体定位以及变形改造的全过程都蕴含着丰富的构造动力学信息。研究花岗岩浆上升、迁移和定位可以探讨构造块体抬升及区域构造动力学。岩体生长方式与构造块体的运动学、动力学有密切的关系,极性生长揭示了上、下构造块体或岩石圈之间的相对的近水平方向剪切运移。变形花岗岩体是一种区域尺度的应变标志体,可以进行岩石有限应变测量和流变学参数估算,为分析区域构造变形特征提供应变参数。以对不同期次、不同变形程度花岗岩体为间接标志体,通过锆石定年可以限定变形的时间,特别是有可能确定早期变形的时间。岩体定位深度的系统研究有利于了解构造块体的抬升和深部构造作用。花岗岩构造与花岗岩成因类型特别是其演变研究的结合是判别构造块体动力学背景以及其转换的有效途径。通过这几方面的系统研究和有机结合,可以提供丰富的构造动力学信息,是否可能发展成较系统的花岗岩构造动力学值得探讨。

STUDIES ON STRUCTURES OF GRANITIC PLUTONS AND GRANITIC TECTONIC DYNAMICS

Granitic plutons might be regarded as good tectonic objects, such as faults and folds. The process from generation of magma, melt segregation, magma ascend, to emplacement as well as deformation rework contained abundant information on tectonic dynamics. Studies on magma ascend, migration and emplacement could provide information on exhumation of tectonic terranes and regional tectonic dynamics. Magmatic accumulation and growth patterns of plutons were closely related to the kinematics and dynamics of tectonic terranes and continental block, and polar growth revealed relative tangential shear movement between upper and lower parts of terranes or crust, or between upper and lower lithospheres. Deformed granitic plutons were good regional-scale strain markers, the finite strain and rheological parameters of which could be easily measured, and used in analysis of regional structures. Granitic plutons with different ages and deformation degrees could be used as good timing markers to constrain timing of deformation, particularly to the timing of early deformation by zircon U-Pb dating. Determination of depth of granitic plutons was helpful for understanding of uplift of terranes and deep tectonism. Integration of structures, origin types and transition of origin types was an effective approach to discrimination of tectonic setting and its transition features. Systematic studies and integration of all of these might provide abundance useful information on tectonic dynamics, and probably develop into a systematic granite tectonic dynamics.