摘要
从中国大陆新生代构造-地貌发生重大改变的地质事实出发,针对中国东部岩石圈减薄的演化过程,构建力学模型,考虑岩石圈各圈层蠕变机制,用数值模拟方法,定量研究同期盆-山耦合的深层动力学机理,对地学研究提出的盆-山伸展动力学模式进行了理论探讨和验证。研究表明,岩石圈的增厚、减薄与岩石圈下部的热活动、热对流关系密切,是同期盆-山伸展耦合体系形成的重要影响因素之一。盆-山体系的热对流动力边界条件,需要同时考虑上浮力和剪切拖曳力的作用,才能形成与实际构造-地貌相符的形变、应力条件,缺一不可。对岩石圈蠕变特征的研究表明,在受恒力作用时,各圈层岩石中的应力、应变随时间改变,初期迅速增加,到达峰值之后平稳下降。应力的松弛现象对研究构造活动中一些常见的地质现象十分有意义。
A geomechanical model for the evolutionary process of lithospheric thinning in eastern China is constructed in light of the geological fact that significant changes took place in Cenozoic tectonics and geomorphology on the continent of China. Assuming that the various layers of the lithosphere are made of creep materials, the deep-level dynamic mechanism of synchronous basin-mountain coupling is quantitatively studied by using the numerical simulation method. A dynamic model of basin-mountain extension proposed by some geologists is theoretically discussed and verified. Study shows that lithospheric thickening or thinning is closely related to the thermal activity or thermal convection beneath the lithosphere and is one of the important factors affecting the formation of the synchronous basin-mountain coupling system. For the dynamic boundary condition of thermal convection of the basin-mountain system, only when both the upward buoyant force and the horizontal shear drag force caused by the thermal convection act on the bottom of the lithosphere, can the stress and strain conditions that accord with the actual tectonics and geomorphology be formed. Study of the creep features of the lithosphere shows that when the lasting forces act on the boundary, the stress and strain of various layers of the lithosphere vary with time. They increase rapidly in the initial stage and decrease steadily after reaching the peak value. The phenomenon of stress relaxation has great significance for the study of some common geological phenomena in tectonic activities.
出处
《地质力学学报》
CSCD
2005年第3期204-214,共11页
Journal of Geomechanics
基金
国家自然科学基金(No.19972064)
国土资源部科技研究项目(No.991005)资助。
关键词
岩石圈减薄
盆-山体系
动力机制
蠕变方程
数值模拟
lithospheric thinning
basin-mountain system
dynamic mechanism, creep equation
numerical simulation
