Collaborative Research: Geochemistry and Whole Mantle Convection

研究人员对海洋地壳的生成和再循环在地球化学非均质性形成中的作用很感兴趣。海洋地壳的形成是一个基本的分异过程，导致了微量元素和体积成分的明显变化。密度和流变学的相关变化对地幔动力学和地幔混合具有重要影响。我们的主要假设是，海洋地壳的形成和再循环可以解释地球化学观测的很大一部分。该项目的中心目标是研究成分密度在保持地球化学非均质性中的作用。作为研究人员假设检验方法的一部分，他们将解决以下问题：1)海洋地壳的再循环如何影响地幔化学？2)稀有气体与亲石同位素比值有何关系？3)地球形成过程中的大尺度分异是否可以解释目前观测到的非均质性？该团队将结合地球动力学和地球化学模型来回答这些问题。这为通过量化地幔混合、分馏、分异和脱气的影响来测试概念性思想提供了一个极好的工具。这种方法是基于Van Keken， Ballentine和Hauri之前建立的合作。以前的模型将通过模拟海洋地壳形成、加入亲石同位素以及显著提高空间和时间分辨率而得到改进。Van Keken和一名研究生将负责模型改进和动力学计算，而Hauri和Ballentine将指导假设方法并协助地球化学建模。协作方面是这一建议的重要组成部分。这个项目将使我们更好地了解地球的热化学演化过程。它将有助于发展基本的动力学建模工具，并提供跨学科的整合，国际合作，以及定量地球物理和地球化学学生的教育。

Van Keken, HauriEAR-0229962, 0229755The investigators are interested in the role that the generation and recyclingof oceanic crust plays in the formation of geochemical heterogeneity.The formation of oceanic crust is a fundamental differentiation process thatcauses distinct variations in trace element and bulk composition. The relatedvariations in density and rheology have important consequences for mantledynamics and mantle mixing. Our main hypothesis is that the formation andrecycling of oceanic crust can explain a vast proportion of the geochemicalobservations. The central goal of this project is to study the role thatcompositional density plays in preserving geochemical heterogeneity.As part of the investigators' hypothesis testing approach they will address following questions: 1) How does the recycling of oceanic crust affect mantle chemistry? 2) What are the relationships between noble gas and lithophile isotope ratios? 3) Is it possible that the large-scale differentiation during Earth'sformation accounts for the presently observed heterogeneity? The team will use a combination of geodynamical and geochemical modeling toanswer these questions. This provides an excellent tool to test conceptualideas by quantifying the effects of mantle mixing, fractionation,differentiation, and degassing. The approach is based on previously establishedcollaboration between Van Keken, Ballentine and Hauri. Previous models will beimproved by the modeling of oceanic crust formation, incorporation oflithophile isotopes, and significantly higher spatial and temporal resolution.Van Keken and a graduate student will be responsible for the model improvementsand dynamical computations, while Hauri and Ballentine will guide the hypothesistesting approach and aid the geochemical modeling. The collaborative aspects arean essential component of this proposal. This project will lead to a better understanding of the processes that areresponsible for the thermal and chemical evolution of our planet. It will aidin the development of essential dynamical modeling tools and providecross-disciplinary integration, international collaboration, and educationof students in quantitative geophysics and geochemistry.