Linking the deep structures of the cratons of Africa and South America by integrated geophysical modelling

在拟议的研究中，我们将综合重力、地震、地热和矿物物理数据，以调查非洲和南美洲地区的岩石圈。对于这两个大陆，以前已经提出了反映构造年龄的成分变化，这在很大程度上影响了地震速度和密度等地球物理观测值。大陆之间的比较可以解释地幔内部演化的相似性和差异性，单一的地球物理技术分析无法清楚地区分上地幔的成分效应和附加热效应。此外，地壳中的源限制了上地幔源的探测，特别是在重力研究中。对于这两个区域，地震和地震学研究中已有地壳模型，我们将利用GOCE卫星使命新提供的重力梯度。卫星重力梯度的优势在于其主要灵敏度限于100 km以内的深度，因此可以用来验证（下）地壳和上地幔的密度结构。新的数据集允许进一步区分与更高的信心比以前的研究岩石圈和岩石圈下的重力场组件之间。然后利用重力残差来估计动态地形和地幔动力学对大陆地壳内部现状的作用，例如大陆沉积盆地的演化。此外，结果将被用来模拟地幔流的温度变化转换为粘度变化，而密度的不均匀性驱动对流。将建立地幔流速度模型，并与所获得的结构模型一起进行分析，以确定影响岩石圈组成结构的过程。

In the proposed study, we are going to integrate gravity, seismic, geothermal and mineral physical data for investigations of the lithosphere of the regions of Africa and South America. For both continents, compositional changes reflecting the tectonothermal age have been proposed previously, which largely affect geophysical observables as seismic velocities and densities. The comparison between the continents allows to decipher the similarities and differences in the evolution of the cratonic interior.Analysis of a single geophysical technique does not allow to distinguish clearly between compositional and additional thermal effects in the upper mantle. Furthermore, sources in the crust limit the detection of upper mantle sources, especially in gravity studies. For the two regions, crustal models exist from seismic and seismological studies and we will make use of the newly available gravity gradients from the GOCE satellite mission. Satellite gravity gradients have the advantage that their main sensitivity is limited to a depth of less than 100 km, so they can be used to validate the density structure in the (lower) crust and upper mantle. The novel data set allows further to discriminate with a higher confidence than in previous studies between lithospheric and sub-lithospheric components in the gravity field. The gravity residuals are then exploited to estimate dynamic topography and the role of mantle dynamics on the present state of the cratonic interior, e.g the evolution of sedimentary basins, of the continents. In addition, the results will be used to model mantle flow by converting the temperature variations to viscosity variations, while the density heterogeneity drives convection. Models of mantle flow velocities will be established that are analysed jointly with the obtained structural models to characterize the processes that affect the compositional structure of the lithosphere.