Numerical Models of Mantle Convection and Plate Tectonics

Richards Ear-0003553地球动力学专家最近跨越了一个重要的门槛，他们表明，在包括简单的岩石圈破坏流变学描述的数值模型中，地幔对流的板块构造风格是自相矛盾的。研究人员建议进一步发展地幔对流和板块构造的三维球面模型，以包括对岩石圈破裂或板块边界形成的更全面的物理处理。他们将使用标量“损伤理论”的张量延伸来解释根据最大剪切应变定向的增强弱化。一个合理而有意义的假设是，这种模式中自然会出现交替的山脊变换几何结构，俯冲带的单边性也可能与断裂带深层定向应变速率减弱有关。岩石圈破裂流变学的各向异性公式需要张量粘度的拉格朗日跟踪或平流--这是一项非常重要的任务，因为他们开发了跟踪地幔对流中化学物质的方法。研究人员还建议继续对显着的亚石层低粘性带(LVZ)在促进板块构造方面的作用进行重点研究。这笔赠款支持的其他相关工作将包括正在进行的地幔混合、地核和地幔的热耦合、扩散板块边界的动力学以及热化学羽流与板块尺度流动的相互作用的研究。

Richards EAR-0003553 Geodynamicists have recently crossed a significant threshold by showing that plate tectonic styles of mantle convection arise self-consistently in numerical models that include simple rheological descriptions of lithospheric failure. The investigators propose to further develop 3-D spherical models of mantle convection and plate tectonics to include a more complete physical treatment of lithospheric failure, or plate boundary formation. They will use a tensor extension of scalar "damage theory" to account for enhanced weakening oriented according to maximum shear strain. A reasonable and significant hypothesis is that alternating ridge-transform geometries arise naturally in such models, and that the one-sidedness of subduction zones may also be related to oriented strain-rate weakening deep within fault zones. An anisotropic formulation of lithospheric failure rheology requires Lagrangian tracking, or advection, of tensor viscosity -- a non-trivial task facilitated by methods they have developed for tracking chemical species in mantle convection. The investigators also propose to continue their focussed investigation into the role of a pronounced sublithospheric low viscosity zone (LVZ) in promoting plate tectonics. Other related work supported by this grant will include ongoing studies of mantle mixing, thermal coupling of the core and mantle, the dynamics of diffuse plate boundaries, and interactions of thermo-chemical plumes with plate-scale flow.