太古宙多岩浆通道与穹脊构造的动力学关联

Dynamic connection between Archean magma vents and Dome-and-Keel Structures

太古宙时期岩石圈的主要散热方式是岩浆活动,岩浆活动既为岩石圈提供了新的物质,也为岩石圈变形提供了动力条件.目前已发现残留的太古宙构造变形记录显示,那时"大陆"内部广泛发育与垂向运动过程有关的穹脊构造.但对于这种垂向构造是如何与太古宙岩浆活动联系起来的,目前还不清楚.为了研究岩浆的动力作用与穹脊构造间的关系,基于有限差分数值模拟方法设置了大小为879 km×400 km的二维数值模型,通过设置多岩浆通道条件模拟太古宙岩浆的侵入过程.实验结果显示出岩浆活动弱化了岩石圈并造成岩石圈的强烈变形.其中,岩浆通道的正上方呈现出正地形,并形成TTG穹窿.密集排布的岩浆通道之间呈现负地形,形成绿岩带坳陷.穹窿在演化过程中发生水平扩张,导致绿岩带不断收窄形成"钱袋子"构造样式,二者共同组成穹脊构造.本研究认为将岩浆活动作为调节岩石圈变形的条件符合太古宙地质背景.岩浆通道条件能为穹脊构造的产生提供驱动力,是造成太古宙岩石圈变形的重要因素.

Magmatism is the main method for lithospheric cooling in Archean.It not only produces new materials,but also provides power for lithospheric deformation.The records of Archean deformation remained up to present suggest that the dome-and keelstructure related to the vertical movement are widely developed in the interiors of continental cratons at that time.However,it is not clear how the vertical structures work with the Archean magmatic activity.In order to make the study more intuitively,we made a two-dimensional numerical model in size of 879×400 km2 based on the finite difference numerical simulation method and then tried to work out the intrusion process by setting magma conditions.The experimental results show that the magma vent array weakens the lithosphere and causes strong deformation of the lithosphere.The TTG domes are formed on the top of the magma vents.There is a negative topography between the magma channels.There is a negative topography,a depression,between the dense magma vents.During the evolution of the dome,it will expand horizontally resulting in the narrowing of the greenstone belt and the appearance of"bag"style.They constitute the dome-and keel-structure.In our study,considering magmatism as a condition of lithosphere deformation is consistent with the facts from the Archean geological background.The magma vent array,as an important factor for lithosphere deformation,provides driving force for the formation of the dome-and-keel structure.