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.

地球中的元素流动性驱动全球地球化学循环并将元素富集到矿床中。这种流动性很少可以直接测量，尤其是对于地球深处或地球最早的历史而言。相反，它必须根据岩石记录重建，特别是根据在感兴趣的过程中形成的矿物的化学成分。尽管在开发读取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取其成分的了解，派生数据仍然存在很大的模糊性。事实上，没有任何模型能够正确预测矿物质对元素的吸收量为数十至数千毫克/千克。在痕量水平上，晶格应变理论 (LST) 提供了一个框架来预测从熔体和流体中吸收元素，表明它是由晶格中元素在尺寸和电荷方面的不匹配控制的。然而，LST 仅在“无限稀释”时有效，并且在较高浓度下会观察到强烈偏差。因此，LST 在对成矿系统进行极端富集建模时无法提供有意义的浓度数据。热力学固溶体模型允许根据元素替代的吉布斯自由能对高浓度下的元素结合进行建模（例如斜长石中的 Ca+Al = Na+Si）。然而，热力学数据的不确定性不允许外推至低浓度。因此，迫切需要一个模型来预测所有浓度的元素吸收。该研究计划旨在通过获得对元素如何容纳在矿物质中的基本见解，开发一种统一的理论来解释和预测整个浓度范围内的元素吸收。将进行实验来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相结合，并通过原子模拟对原子尺度上失配元素周围的局部晶格进行预测建模。矿物的元素和同位素组成包含有关矿物生长环境中的压力、温度、年龄和元素迁移率的信息宝库。该研究项目中形成的基本见解将使我们能够提取这些信息，而不会出现目前削弱该方法的模糊性。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成分，再到矿石的形成。此外，它在工业中具有直接应用，其中材料的所需行为（例如作为催化剂）与丰富的功能元素直接相关。因此，这项研究解决了加拿大公众的直接担忧，包括开发用于绿色技术的新型材料、修复废物、解决日益减少的自然资源以及气候变化的影响。