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

元素在地球上的流动推动了全球的地球化学循环，并将元素浓缩到矿床中。这种流动性很少直接测量，特别是对于地球深处或地球最早的历史来说。相反，它必须从岩石记录中重建，特别是从感兴趣的过程中形成的矿物化学中重建。尽管在开发读取矿物记录的工具方面取得了巨大进展，但由于缺乏对矿物成分的了解，衍生数据仍然存在重大模糊性。事实上，没有一个模型能正确预测矿物质对元素的摄取量从几十毫克/公斤到几千毫克/公斤。 在痕量水平上，晶格应变理论(LST)提供了一个框架来预测元素从熔体和流体中的吸收，表明它是由元素在晶格中的大小和电荷失配控制的。然而，LST只有在无限稀释时才有效，并且在较高浓度下观察到强烈的偏差。因此，LST不能提供有意义的浓度数据来模拟成矿系统的极端富集度。热力学固溶体模型允许从元素替代的吉布斯自由能(例如斜长石中的Ca+Al=Na+Si)模拟高浓度的元素掺入。然而，热力学数据的不确定性不允许对低浓度进行外推。因此，迫切需要一种模型来预测所有浓度下的元素吸收。 这项研究计划旨在开发一个统一的理论，通过对元素在矿物中的调节方式获得基本的见解，来解释和预测元素在整个浓度范围内的吸收。将进行实验来表征矿物晶格对失配元素掺入的响应。这将与直接测量晶格尺寸和弹性相结合，并通过原子模拟在原子尺度上对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关于矿物生长环境中的压力、温度、年龄和元素流动性的信息宝库。在这个研究项目中形成的基本见解将使我们能够提取这些信息，而不会出现目前阻碍这种方法的模棱两可的情况。这使我们能够解决关键的物质和地球科学问题，从俯冲带元素循环，到早期地壳和海洋的成分，再到成矿作用。此外，它在工业中有直接的应用，在工业中，材料的所需性能(例如作为催化剂)与功能元素的丰度直接相关。因此，这项研究解决了加拿大公众的直接关切，包括为绿色技术开发新材料、补救废物、解决自然资源日益减少的问题，以及气候变化的影响。

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.