Towards a unified theory for element uptake by minerals over the full range of element concentrations

建立矿物在整个元素浓度范围内吸收元素的统一理论

• 批准号: RGPIN-2020-04173
• 负责人: vanHinsberg, Vincent
• 金额: $ 2.62万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=751019
• 关键词: Towards; unified; theory; element; uptake

Element mobility in the Earth drives global geochemical cycles and concentrates elements into ore deposits. This mobility can rarely be measured directly, especially not for the deep Earth or the earliest history of our planet. Instead, it has to be reconstructed from the rock record, in particular from the chemistry of minerals that formed in the process of interest. Despite huge progress in developing tools to read the mineral record, there is still major ambiguity in derived data because of a lack of understanding in how minerals get their composition. Indeed, no model correctly predicts the uptake of elements by minerals from the tens to thousands of mg/kg. At trace levels, Lattice-Strain Theory (LST) provides a framework to predict the uptake of elements from melts and fluids, showing it to be controlled by an element's mismatch in the crystal lattice in terms of size and charge. However, LST is only valid at "infinite dilution" and strong deviations are observed at higher concentrations. As a result, LST does not provide meaningful concentration data in modeling ore forming systems to their extreme enrichment. Thermodynamic solid solution models allow for modeling of element incorporation at high concentrations from the Gibbs free energy of element substitutions (e.g. Ca+Al = Na+Si in plagioclase). However, uncertainties in thermodynamic data do not permit extrapolations to low concentrations. There is therefore an urgent need for a model to predict element uptake at all concentrations. This research program aims to develop a unified theory to explain and predict element uptake over the full range of concentrations by gaining fundamental insights into how elements are accommodated in minerals. Experiments will be conducted to characterise the response of mineral lattices to mismatching element incorporation. This will be combined with direct measurements of crystal lattice dimensions and elasticity, and with predictive modelling of the local lattice around mismatching elements at the atom-scale by atomistic simulations. The elemental and isotopic composition of minerals contains a treasure trove of information on pressure, temperature, age, and element mobility in the minerals' growth environment. The fundamental insights developed in this research program will permit us to extract this information without the ambiguity that currently cripples this approach. This allows us to address key material and geoscience questions, from subduction zone element cycling, to the compositions of the Early Earth crust and oceans, to ore formation. Moreover, it has direct applications in industry where the desired behaviour of a material, for example as a catalyst, is directly linked to the abundance of functional elements. This research thereby addresses direct concerns to the Canadian general public, including developing novel materials for green technologies, remediating waste, addressing dwindling natural resources, and the impact of climate change.

地球中的元素迁移率驱动全球地球化学循环，并将元素集中到矿石沉积物中。这种流动性很少直接衡量，尤其是对于地球的深层或我们星球的最早历史而言。取而代之的是，它必须从岩石记录中重建，尤其是在感兴趣过程中形成的矿物质的化学。尽管在开发阅读矿物记录的工具方面取得了巨大进展，但由于缺乏对矿物如何获得其成分的了解，因此衍生数据仍然存在重大歧义。实际上，没有模型可以正确预测矿物从数十毫克/kg的矿物的吸收。在痕量水平上，晶格 - 应变理论（LST）提供了一个框架来预测熔体和流体中元素的吸收，表明它是由晶体晶格中元素的不匹配在大小和电荷方面控制的。但是，LST仅在“无限稀释”时有效，并且在较高浓度下观察到强偏差。结果，LST在建模矿石形成系统的极端富集中没有提供有意义的浓度数据。热力学固体溶液模型允许建模元素取代的Gibbs自由能（例如Ca+Al = Na+Si中的gibbs自由能中的元素掺入）。但是，热力学数据中的不确定性不允许推断到低浓度。因此，迫切需要模型来预测各个浓度的元素吸收。该研究计划旨在开发一种统一的理论，以通过获得对矿物质中元素的基本见解来解释和预测全部浓度的元素吸收。将进行实验，以表征矿物晶格对不匹配元素掺入的响应。这将与晶格尺寸和弹性的直接测量结合在一起，并通过原子模拟在原子尺度的不匹配元素周围对局部晶格进行预测建模。矿物质的元素和同位素组成包含有关矿物生长环境中压力，温度，年龄和元素迁移率的信息。该研究计划中开发的基本见解将使我们能够在当前瘫痪这种方法的情况下提取此信息。这使我们能够解决关键的材料和地球科学问题，从俯冲带元素循环到早期地壳和海洋的组成，再到矿石形成。此外，它在行业中有直接的应用，其中材料的所需行为（例如作为催化剂）直接与功能元素的丰富性直接相关。因此，这项研究对加拿大公众的直接关注进行了解决，包括开发绿色技术的新型材料，修复废物，解决减少的自然资源以及气候变化的影响。