CSEDI: Geochemical Evolution of the Earth's Mantle Constrained by Observations and Dynamical Modeling

CSEDI：观测和动力学模型约束下的地幔地球化学演化

基本信息

批准号：
1664642
负责人：
Peter van Keken
金额：
$ 29.38万
依托单位：
Carnegie Institution of Washington
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-08-01 至 2021-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1664642&HistoricalAwards=false
关键词：
CSEDI Geochemical Evolution Earth Mantle

项目摘要

This project seeks to advance scientific knowledge about how the Earth's interior has changed over geologic time, due to the very slow motions caused by the sinking of tectonic plates into the interior and the rise of hot buoyant material from the deep Earth, all of which work to mix the Earth's mantle. These convective motions have the potential to move tectonic plates from the surface all the way to the core-mantle boundary (CMB), and to return material from the CMB where it can contribute to near-surface melting that produces volcanoes at mid-ocean ridges and at oceanic hotspots (such as Hawaii and others). The investigators will use high-performance computer simulations of these convective motions to study the flow of the Earth's interior and how this flow is modified by changes in mineralogy that occur at the high pressures of the Earth's deep interior; the computational models will be enhanced by the inclusion of millions of passive tracer particles that record changes in geochemistry that occur when the mantle melts at the surface, when plates sink and mix into the Earth's interior, and when sediment eroded from the continents is brought into the Earth's interior by these processes. The geochemical changes recorded by the tracer particles will be compared with geochemical data from volcanoes to test whether the flow in the deep Earth continues all the way to the core, or whether the interior flows as separate layers with minimal mixing between them. The knowledge gained from this project will provide information on how the tectonic motions at the surface of the Earth affect mixing in the interior, and how this mixing in turn has altered the flow of various elements from the interior to the continents thus providing information on how the continents have grown and eroded over Earth's geologic history.In this project the investigators will focus on documenting the geochemical evolution of the mantle in a series of high-resolution numerical convection models that examine the degree of mantle layering, stratification, and convective isolation that occur when realistic compressible equations of state are used to describe the physical properties of the mantle. The use of a compressible mantle will allow us to model mineralogical phase transitions in a rigorous way. When combined with laboratory data on the P-T-strain rate dependence of mantle viscosity, conductivity and thermal expansion, these features of the model will produce the most physically realistic description of the extent of mantle layering that can occur due to depth-dependent density and viscosity associated with known phase boundaries. The model series will be further constrained to only those models that match the known ranges in major geophysical and geochemical observations (convective vigor, mantle temperature, heat flow, plate velocities, rate of internal heating, composition and mass of the atmosphere and continental crust, etc.). The geochemistry of the model space will be calculated from millions of active numerical tracers embedded in the mantle flow, that will each record the trace element fractionation and associated isotopic evolution they experience when their evolution is punctuated by melting, degassing, and continental extraction events that occur at the surface of the model. The team will model explicitly the evolving isotope geochemistry of both lithophile and noble gas isotope systems in the convecting mantle, continental crust and atmosphere, and quantitatively compare the model output with geochemical data to test the viability of our models.

该项目旨在推进有关地球内部在地质时期如何变化的科学知识，这是由于构造板块下沉到内部造成的非常缓慢的运动以及来自地球深处的热浮力物质的上升，所有这些都起作用混合地幔。这些对流运动有可能将构造板块从地表一直移动到地核-地幔边界 (CMB)，并从 CMB 返回物质，从而促进近地表融化，从而在洋中脊产生火山以及海洋热点地区（例如夏威夷等）。研究人员将使用这些对流运动的高性能计算机模拟来研究地球内部的流动，以及地球内部深处高压下发生的矿物学变化如何改变这种流动；计算模型将通过包含数以百万计的被动示踪粒子而得到增强，这些粒子记录了当地幔在地表融化时、当板块下沉并混合到地球内部时以及当从大陆侵蚀的沉积物被带入地球时发生的地球化学变化。地球内部通过这些过程。示踪粒子记录的地球化学变化将与火山的地球化学数据进行比较，以测试地球深处的流动是否一直持续到地核，或者内部是否作为单独的层流动，并且它们之间的混合最小化。从该项目中获得的知识将提供有关地球表面的构造运动如何影响内部混合的信息，以及这种混合如何反过来改变各种元素从内部到大陆的流动，从而提供有关如何影响内部混合的信息。在地球的地质历史中，大陆不断生长和侵蚀。在这个项目中，研究人员将重点记录地幔的地球化学演化，通过一系列高分辨率数值对流模型来检查地幔分层程度，当使用现实的可压缩状态方程来描述地幔的物理特性时，会发生分层和对流隔离。使用可压缩地幔将使我们能够以严格的方式模拟矿物相变。当与地幔粘度、电导率和热膨胀的 P-T 应变率依赖性的实验室数据相结合时，该模型的这些特征将对由于深度相关的密度和粘度而可能发生的地幔分层程度进行最物理真实的描述与已知的相边界相关。该模型系列将进一步仅限于那些与主要地球物理和地球化学观测中已知范围相匹配的模型（对流活力、地幔温度、热流、板块速度、内部加热速率、大气和大陆地壳的成分和质量、 ETC。）。模型空间的地球化学将通过嵌入地幔流中的数百万个活跃数值示踪剂进行计算，每个示踪剂将记录微量元素分馏和相关的同位素演化，当它们的演化被熔化、脱气和大陆萃取事件打断时，这些示踪剂将被记录下来。发生在模型的表面。该团队将明确模拟对流地幔、大陆地壳和大气中亲石和稀有气体同位素系统不断演变的同位素地球化学，并将模型输出与地球化学数据进行定量比较，以测试我们模型的可行性。

项目成果

期刊论文数量（6）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Subducted oceanic crust as the origin of seismically slow lower-mantle structures

俯冲洋壳是慢震下地幔结构的起源

DOI：
10.1186/s40645-020-00327-1
发表时间：
2020-02-21
期刊：
Progress in Earth and Planetary Science
影响因子：
3.9
作者：
T. Jones;R. Maguire;P. V. van Keken;J. Ritsema;P. Koelemeijer
通讯作者：
P. Koelemeijer

An Exactly Mass Conserving and Pointwise Divergence Free Velocity Method: Application to Compositional Buoyancy Driven Flow Problems in Geodynamics

精确质量守恒和逐点发散自由速度方法：在地球动力学中组合浮力驱动流问题中的应用

DOI：
10.1029/2020gc009349
发表时间：
2021-04
期刊：
Geosystems
影响因子：
0
作者：
Sime, Nathan;Maljaars, Jakob M.;Wilson, Cian R.;van Keken, Peter E.
通讯作者：
van Keken, Peter E.

Burying Earth's Primitive Mantle in the Slab Graveyard

将地球的原始地幔埋在石板墓地中

DOI：
10.1029/2020gc009396
发表时间：
2021-03
期刊：
Geosystems
影响因子：
0
作者：
Jones, T. D.;Sime, N.;van Keken, P. E.
通讯作者：
van Keken, P. E.

Earth’s missing argon paradox resolved by recycling of oceanic crust

洋壳循环利用解决了地球缺氩悖论

DOI：
10.1038/s41561-021-00870-6
发表时间：
2022-01
期刊：
Nature Geoscience
影响因子：
18.3
作者：
Tucker, Jonathan M.;van Keken, Peter E.;Ballentine, Chris J.
通讯作者：
Ballentine, Chris J.

Origins of the terrestrial Hf-Nd mantle array: Evidence from a combined geodynamical-geochemical approach

陆地 Hf-Nd 地幔阵列的起源：来自地球动力学-地球化学联合方法的证据

DOI：
10.1016/j.epsl.2019.04.015
发表时间：
2019-07-15
期刊：
Earth and Planetary Science Letters
影响因子：
5.3
作者：
Rosemary E. Jones;P. V. van Keken;E. Hauri;J. Tucker;J. Vervoort;C. Ballentine
通讯作者：
C. Ballentine