Tracking sodium in Earths deep mantle

追踪地球深层地幔中的钠

• 批准号: 2242904
• 负责人: Susannah Dorfman
• 金额: $ 45.61万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-15 至 2026-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2242904&HistoricalAwards=false
• 关键词: Tracking; sodium; Earths; deep; mantle

Sodium is concentrated in regions of the Earth where fluids cycle within the planet as well as in oceanic crust sinking and mixing into the mantle. Because sodium affects melting of rocks and increases electrical conductivity of fluids, its chemistry at high pressures and temperatures of Earth’s interior is important to understanding deep Earth carbon and water cycles. This study will observe the quantity and mineral forms of sodium in the Earth’s largest layer, the lower mantle. Experiments and computer simulations will test sodium storage in the most abundant oxide mineral in the planet, which has the same atomic structure as rock salt. The project will support training for a graduate student and undergraduate assistant and a partnership with the MSU Museum to produce, present, and evaluate modular exhibits on salt geology and crystal structures for a public audience. The host phase and capacity for sodium in Earth’s mantle are important for modeling deep Earth cycles of essential volatiles and reading the mantle record of plate tectonics. (Mg,Fe)O ferropericlase may be the major host for sodium in Earth’s interior. Systematic experiments using laser-heated diamond anvil cells will measure the concentration of sodium in (Mg,Fe)O under sodium-saturated conditions and in equilibrium with the other major lower mantle phases bridgmanite and/or davemaoite. Complementary density functional theory calculations will test the relative favorability of mechanisms for dissolving sodium in lower mantle phases. In combination these methods will be used to determine the dominant lower-mantle host phase for sodium and the seismic properties of Na-bearing lower mantle. Improved constraints on the high-pressure mineralogy of sodium can be applied to update thermodynamic and geophysical modeling of the mantle for more accurate determination of mantle composition and heterogeneity. The incorporation of archetypal alkali metal sodium into (Mg,Fe)O oxide will also produce insights into systematics of salts and bonding at high pressure.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

钠集中在地球内部流体循环的区域以及下沉并混合到地幔中的洋壳中，因为钠会影响岩石的熔化并增加流体的电导率及其在地球内部高压和高温下的化学性质。对于了解地球深层碳和水循环非常重要。这项研究将观测地球最大层（下地幔）中钠的数量和矿物形态。实验和计算机模拟将测试地球最丰富的氧化物矿物中的钠储存情况。该项目将支持研究生和本科生助理的培训，并与密歇根州立大学博物馆合作，为公众制作、展示和评估有关盐地质学和晶体结构的模块化展览。地球地幔中钠的宿主相和容量对于模拟地球深层基本挥发物循环和读取板块构造的地幔记录非常重要，(Mg,Fe)O 铁方镁石可能是地球内部钠的主要宿主。使用激光加热金刚石砧池的系统实验将测量钠饱和条件下 (Mg,Fe)O 中的钠浓度，并与其他主要下地幔相桥锰矿和/或达维茂石相平衡，将测试互补密度泛函理论计算。下地幔相中钠溶解机制的相对有利性将结合使用这些方法来确定钠的主要下地幔主相和含钠下地幔的地震特性。改进的钠高压矿物学约束可用于更新地幔的热力学和地球物理模型，以便更准确地确定地幔成分和异质性。将原型碱金属钠掺入 (Mg,Fe)O 氧化物中也将产生。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。