Supercontinent formation from stochastic collision and mantle convection models
Supercontinent formation from stochastic collision and mantle convection models
复制标题
DOI：
10.1016/j.gr.2008.10.002
复制
发表时间：
2009-06
影响因子：
6.1
通讯作者：
N. Zhang;S. Zhong;Allen K. McNarmara
中科院分区：
文献类型：
--
作者：
N. Zhang;S. Zhong;Allen K. McNarmara
过去10亿年（Ga）的大规模构造活动主要是Rodinia和Pangea超大陆的组装和裂解。控制超级大陆组装的机制尚不清楚。在这里，我们研究了组装的超大陆与1）随机移动的大陆块体的随机模型和2）3-D地幔对流与大陆块体的球形模型。对于随机模型，我们确定了所有块体在球面上组装成单个超大陆所需的时间。我们发现，我们的随机模型的组装时间显着长于推断盘古和Rodinia。然而，我们的研究也表明，组装时间从随机模型是敏感的随机分配大陆运动的模型中的规则。在我们的地幔对流动力学模型中，大陆块体被模拟为可变形的、成分上与地幔不同的物质。我们发现地幔对流平面形状对超大陆组装有重要影响。对于具有中等强度岩石圈和相对于上地幔的下地幔导致1度地幔对流的模型，大陆块体总是在2.25亿年（Ma）内组装成超大陆，这一组装时间与Pangea和Rodinia的推断一致。然而，对于本质上小规模的地幔流的模型，我们发现，即使当大陆块合并形成一个超大陆，组装时间太长，超大陆区域以外的对流结构的波长太小，与观察到的。
The large-scale tectonics in the last billion years (Ga) are predominated by the assembly and breakup of supercontinents Rodinia and Pangea. The mechanisms controlling the assembly of supercontinents are not clear. Here, we investigate the assembly of a supercontinent with 1) stochastic models of randomly-moving continental blocks and 2) 3-D spherical models of mantle convection with continental blocks. For the stochastic models, we determined the time required for all the blocks to assemble into a single supercontinent on a spherical surface. We found that the assembly time from our stochastic models is significantly longer than inferred for Pangea and Rodinia. However, our study also suggests that the assembly time from stochastic models is sensitive to the rules for randomly assigning continental motion in the models. In our dynamic models of mantle convection, continental blocks are modeled as deformable and compositionally distinct materials from the mantle. We found that mantle convective planform has significant effects on supercontinent assembly. For models with moderately strong lithosphere and the lower mantle relative to the upper mantle that lead to degree-1 mantle convection, continental blocks always assemble to a supercontinent in ∼250 million years (Ma) and this assembly time is consistent with inferred for Pangea and Rodinia. However, for models with intrinsically small-scale mantle flows, we found that even when continental blocks merge to form a supercontinent, the assembly times are too long and the convective structures outside of supercontinent regions are of too small wavelengths, compared with observed.