Forward modelling of mantle density anomalies from geodynamic considerations

我们从地球动力学的先验考虑出发，对固体地球，即地幔和岩石圈进行了详细的质量平衡分析。对于岩石圈和上地幔，我们将建立一个已公布的三维密度模型(3SMAC，Nataf和Ricard[1996])。对于更深的地幔，我们将根据全球地幔环流模式中同化的板块运动历史来推断热致密度异常。地幔对流模型的主要进展包括(1)地幔矿物学的热力学自洽公式和(2)非常高的数值分辨率，足以(首次)以类似地球的对流强度解析全球地幔流动。后者的好处是在适合S地幔的时间和长度尺度上分解热边界层。我们将使用正演模式来更好地了解热上涌对地幔密度收支的影响。这一点很重要，因为最近的地球动力学研究支持跨越核地幔边界的热流比先前估计的更大。我们将测试地幔密度模型对一系列核心热流值的敏感性。

We propose a detailed mass budget analysis of the solid Earth, that is mantle and lithosphere, from geodynamic a-priori considerations. For the lithosphere and upper mantle, we will build on a published 3-D density model (3SMAC, Nataf and Ricard [1996]). For the deeper mantle, we will infer thermally induced density anomalies from a history of plate motion assimilated in global mantle circulation models. Key advances to the mantle convection model include (1) a thermodynamically self-consistent formulation of the mantle mineralogy and (2) a very high numerical resolution sufficient to resolve (for the first time) global mantle flow at Earthlike convective vigor. The benefit of the latter is to resolve thermal boundary layers at time-and length-scales appropriate for Earth¿s mantle. We will use the forward models to gain better insight on the impact of hot thermal upwellings on the mantle density budget. This is important because recent geodynamic studies have favored a larger heat flux across the core mantle boundary than prior estimates. We will test the sensitivity of mantle density models to a range of core heat flux values.