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

在拟议的研究中，我们将整合重力、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，先前已经提出了反映构造热年龄的成分变化，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破译克拉通内部演化的相似和不同之处。对单一地球物理技术的分析不能清楚地区分上地幔的成分和附加热效应。此外，地壳中的震源限制了上地幔震源的探测，特别是在重力研究中。对于这两个区域，地壳模型来自地震和地震学研究，我们将利用GOCE卫星任务新获得的重力梯度。卫星重力梯度的优点是其主要灵敏度限制在100公里以下，因此可以用来验证(下)地壳和上地幔的密度结构。与以前的研究相比，新的数据集允许以更高的置信度进一步区分重力场中的岩石圈和岩石圈以下的成分。然后利用重力残差来估计动态地形和地幔动力学对克拉通内部现状的作用，例如大陆沉积盆地的演化。此外，结果将被用于模拟地幔流动，通过将温度变化转换为粘度变化，而密度不均匀驱动对流。将建立地幔流动速度模型，并结合所获得的结构模型进行分析，以描述影响岩石圈成分结构的过程。

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.