太古宙岩石圈构造变形过程与岩浆作用的数值模拟研究

Numerical Simulation of the Structural Deformation Process and Magmatism of the Archaean Lithosphere

太古宙岩石圈构造变形是岩石圈与软流圈在高温条件下发生垂向运动的结果,反映了太古宙非板块构造体制下的地球动力学过程。为了解释这个已经消失的过程,前人利用数值模拟方法并结合较少的地质实例,提出了盖子构造、热管构造、湿盖子构造、地幔柱构造等多种可能存在于太古宙的前板块构造体制。这些体制的主要差异源于前人实验中对岩浆作用的简化方式不同,进而导致了对太古宙地球动力学过程认识的不一致性。为了解决上述矛盾,本研究在不简化岩浆运移过程的前提下,讨论了五种可能条件及其组合对太古宙岩石圈构造变形的控制作用。结果显示,太古宙岩石圈强度较高时,只有经充分弱化才可能产生垂向变形。岩浆的存在不仅弱化了岩石圈,还借由自身浮力提供了变形所需的驱动力。地幔柱主要引发岩石圈减薄与底部拆沉,其他因素如岩石圈厚度、地壳性质、薄弱带等并非岩石圈变形的敏感因素。该结论揭示了太古宙岩浆作用对岩石圈构造变形过程起到了重要控制作用。

Deformation of the Archaean lithosphere as a result of vertical movement of lithosphere and asthenosphere under high temperature may reveal geodynamic processes under the Archaean pre-plate tectonics.In order to explain the Archean deformation,various pre-plate tectonic hypotheses have been proposed,such as lid tectonics,heat-pipe tectonics,plume-lid tectonics and mantle plume tectonics by using numerical modeling and geological examples.These different theories arose mainly from some different ways of simplification for magmatism in previous experiments,which leads to the inconsistent interpretations of the Archean geodynamic process.To avoid such contradiction,five possible conditions and their combined models without simplifying the process of magma migration are discussed in this contribution.The numerical experimental results show that the strength of the Archaean lithosphere is high enough so that only full weakening can cause vertical movement.The existence of magma not only weakens the strength of lithosphere,but also provides driving force for buoyant deformation.Other conditions such as lithospheric thickness,crustal properties or weak zone are not sensitive factors for lithosphere deformation.Therefore,this study reveals an impact of magmatism on deformation of the Archaean lithosphere.