Electrical conductivity measurements on lower mantle phases to illuminate structures at the core-mantle boundary region

下地幔相的电导率测量，以照亮核心-地幔边界区域的结构

• 批准号: 521546172
• 负责人: Professorin Dr. Carmen Sanchez-Valle, Ph.D.
• 金额: --
• 依托单位: Institut für Mineralogie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/521546172?language=en
• 关键词: Electrical; conductivity; measurements; lower; mantle

Resolving the complex structure and dynamics of the core-mantle boundary (CMB) region is crucial to understanding the thermal and chemical evolution of the Earth’s interior. This is a timely and challenging task that requires concerted efforts from different disciplines such as mineral physics, seismology and geodynamics. Seismic observations provide evidence for a range of low velocity anomalies associated to structures of different length scales, including the so-called large low velocity provinces (LLVPs) and the ultra-low velocity zones (ULVZs). The origin of this features remains poorly constrained to date although they are probably both thermally and chemically distinct structures. However, because temperature and composition strongly trade-off, seismic velocity anomalies alone cannot resolve the 3D thermo-chemical structure of the mantle. A promising approach is to take advantage of the increasing resolution of the electrical conductivity observations, which can provide additional and independent constrains on the mantle thermo-chemical structure. Yet, attempts to translate electrical conductivity observables into thermal/chemical models have been largely hampered by the lack of experimental data on the electrical conductivity of main phases at relevant pressure (P)-temperature (T) conditions. The aim of this proposal is thus to address this gap of knowledge by providing unique data on the electrical conductivity of iron-rich lower mantle phases and mineral assemblages generated by core-mantle interactions at CMB conditions. This will be achieved by a combination of state-or-the-art laser-heated diamond anvil cells (LH-DAC) experiments, synchrotron X-ray probes and advanced micro-analytical characterization of recovered samples. The new experimental data will be employed to parameterize the pressure, temperature and composition (e.g. iron fractions) dependence of the electrical conductivity of lower mantle phases and to generate an open access electrical conductivity database to support research within SPP DeepDyn and the whole geosciences community. Forward modelling of lower mantle electrical conductivity in thermal/thermo-chemical models, and their confrontation with electrical conductivity observations, will provide new insights into the thermo-chemical state of lowermost mantle structures and their link to electrical conductivity anomalies.

解决核幔边界（CMB）区域的复杂结构和动力学对于理解地球内部的热演化和化学演化至关重要。这是一项及时和富有挑战性的任务，需要矿物物理学、地震学和地球动力学等不同学科的协调努力。地震观测提供了与不同长度尺度的结构相关的一系列低速异常的证据，包括所谓的大低速区（LLVP）和超低速区（ULVZ）。这种功能的起源仍然不受约束的日期，虽然他们可能是热和化学不同的结构。然而，由于温度和成分强烈的权衡，地震速度异常单独不能解决的三维热化学结构的地幔。一个有前途的方法是利用电导率观测的分辨率不断提高，这可以提供额外的和独立的地幔热化学结构的约束。然而，由于缺乏在相关压力（P）-温度（T）条件下主相电导率的实验数据，将电导率观测值转化为热/化学模型的尝试在很大程度上受到阻碍。因此，本提案的目的是通过提供关于富铁下地幔相和在CMB条件下由核幔相互作用产生的矿物组合的电导率的独特数据来解决这一知识差距。这将通过结合最先进的激光加热金刚石对顶砧（LH-DAC）实验、同步加速器X射线探针和对回收样品进行先进的微观分析表征来实现。新的实验数据将用于参数化下地幔相电导率的压力，温度和成分（例如铁分数）依赖性，并生成开放访问的电导率数据库，以支持SPP DeepDyn和整个地球科学界的研究。热/热化学模型中下地幔电导率的正演模拟及其与电导率观测的对抗将为最低地幔结构的热化学状态及其与电导率异常的联系提供新的见解。