Thermochemical Models of Earth's Mantle Convection: New Insight from Fractionation and Outgassing Processes

玄武岩地球化学记录了地幔动力学信息，表明地幔中至少存在五个储集层。然而，这种水库的动力学意义是病态约束。最近，为了协调各种类型的观测数据，出现了几种新的地球动力学模型，其中包括地幔中不同成分的各层。研究人员将通过使用地幔热化学对流的数值模型来评估这些模型和相关模型，以确定不同动力学模型预测的地球化学特征。模拟将包括示踪剂，以代表各种化学物质。考虑到洋脊的部分熔融过程，产生洋壳和岩石圈之间的分馏，并释放到大气中。这些过程还没有包括在以前的大尺度，完全动态，对流模式。模拟跟踪古洋壳，并包括榴辉岩和橄榄岩之间的固有密度变化，以及不均匀的热生产率。研究人员将讨论他们的不同模型再现玄武岩的一些特征的能力，并与热流等地球动力学观测相一致。他们还将测试结果对岩石学和地球动力学参数的敏感性。

Basalt geochemistry records information about mantle dynamics, indicating that there are at least five reservoirs in the mantle. However, the dynamical meaning of such reservoirs is ill-constrained. Efforts to reconcile the full range of types of observational data have recently given rise to several new geodynamic models that include layers of different composition in the mantle. The investigators will evaluate these and related models, by using numerical models of thermo-chemical convection in the mantle to determine the geochemical signatures predicted by different dynamical models. Simulations will include tracers to represent various chemical species. Partial melting processes at ridges are taken into account, yielding fractionation between oceanic crust and lithosphere, and outgassing into the atmosphere. These processes have not been included in previous large-scale, fully dynamic, convective models. The simulations keep track of ancient oceanic crust, and include intrinsic density variations between eclogite and peridotite, as well as inhomogeneous heat production rates. The investigators will address the ability of their different models to reproduce some of the features of basalt, and to be in agreement with geodynamical observations such as the heat flow. They will also test the sensitivity of the results to petrologic and geodynamic parameters.