Towards self-consistent modeling of the martian dichotomy: The influence of one-ridge convection on crustal thickness distribution
Towards self-consistent modeling of the martian dichotomy: The influence of one-ridge convection on crustal thickness distribution
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走向火星二分法的自洽模型：单脊对流对地壳厚度分布的影响
DOI：
10.1016/j.icarus.2009.03.029
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发表时间：
2009
期刊：
影响因子：
3.2
通讯作者：
P. Tackley
中科院分区：
文献类型：
--
作者：
T. Keller;P. Tackley
为了找到火星地壳二分法起源的解释，最近的一些论文研究了分层粘性对1度地幔对流演化的影响，例如Roberts和Zhong [Roberts，J.H.，Zhong，S.，2006. J. Geophys.第111号决议。E06013]和Yoshida和Kageyama [Yoshida，M.，Kageyama，A.，2006. J. Geophys. Res. 111，doi：10.1029/2005JB 003905。B03412]。结果发现，中地幔粘度跳跃，结合高度的温度和深度依赖的流变学，是有效的开发度-1对流在短时间内。火星矿物学可以证明这种分层的粘度分布是合理的。然而，1度对流地形对地壳厚度分布的影响尚未得到证实。究竟是由于岩石圈下的侵蚀和地壳减薄而形成的较薄的地壳，还是由于地壳生产力的增强而形成的较厚的地壳，会在地幔上涌的半球上方形成，这一点并不明显。此外，一般形状的二分法，这不是严格的半球形，尚未得到充分的研究。在这里，我们提出了一个模型的地壳模式产生的数值模拟火星地幔对流，使用有限体积多重网格代码StagYY [Tackley，P. J.，2008.地球物理Int.107，7-18，doi：10.1016/j.pepi.2008.08.005]熔融、地壳形成和化学分异的自洽处理已被添加到三维热对流模型中。这使我们能够获得全球地图的地壳厚度分布，因为它随着时间的推移而演变。所得结果表明，它确实是可能的，形成一个地壳二分法作为一个结果，近1度地幔对流在火星的历史早期。我们发现，一些观察到的模式显示有趣的一阶相似的椭圆形状的火星二分法。在所有模型中，厚地壳区域位于地幔上涌区域之上，地幔上涌区域本身是一个分布在大约一半地球上的脊状结构，我们将这种平面形状描述为“单脊对流”。
In order to find an explanation for the origin of the martian crustal dichotomy, a number of recent papers have examined the effect of layered viscosity on the evolution of a degree-1 mantle convection, e.g. Roberts and Zhong [Roberts, J.H., Zhong, S., 2006. J. Geophys. Res. 111. E06013] and Yoshida and Kageyama [Yoshida, M., Kageyama, A., 2006. J. Geophys. Res. 111, doi:10.1029/2005JB003905. B03412]. It was found that a mid-mantle viscosity jump, combined with highly temperature- and depth-dependent rheology, are effective in developing a degree-1 convection within a short timescale. Such a layered viscosity profile could be justified by martian mineralogy. However, the effect of a degree-1 convective planform on the crustal thickness distribution has not yet been demonstrated. It is not obvious whether a thinner crust, due to sublithospheric erosion and crustal thinning, or a thicker crust, due to enhanced crustal production, would form above the hemisphere of mantle upwelling. Also, the general shape of the dichotomy, which is not strictly hemispherical, has not yet been fully investigated. Here we propose a model of the crustal patterns produced by numerical simulations of martian mantle convection, using the finite-volume multigrid code StagYY [Tackley, P.J., 2008. Phys. Earth Planet. Int. 107, 7–18, doi:10.1016/j.pepi.2008.08.005] A self-consistent treatment of melting, crustal formation and chemical differentiation has been added to models of three-dimensional thermal convection. This allows us to obtain global maps of the crustal thickness distribution as it evolves with time. The obtained results demonstrate that it is indeed possible to form a crustal dichotomy as a consequence of near degree-1 mantle convection early in Mars' history. We find that some of the observed patterns show intriguing first order similarities to the elliptical shape of the martian dichotomy. In all models, the region of thick crust is located over the region of mantle upwelling, which itself is a ridge-like structure spread over roughly one half of the planet, a planform we describe as “one-ridge convection.”