Reactive Transport Modelling of Ore Formation in Sedimentary Basins

沉积物赋存的矿床是锌、铅、铜等贱金属和许多其他大宗和关键金属(如In、Ge、Ga)的主要资源，这些金属对向碳中性社会的过渡具有战略重要性。盆地规模热液系统中的金属矿化是化学和物理过程在不同时间和空间尺度上完美融合的结果，只有通过超出矿床尺度的观察和研究才能定量地了解这些系统。数值过程模型有可能确定对成矿的一级控制，并对热液系统产生世界级矿床的可行性和效率提供物理和化学约束，这可能有助于指导未来的勘探。近年来在模拟方面取得的重大进展要么集中在热力学--地球化学流体-岩石相互作用方面，要么集中在物理水文学方面，而水热系统的全反应输运模拟仅限于简化系统。在拟议的项目中，我们将使用地化模型GEMS3和流体流动模型CSMP++来开发和应用沉积盆地中的成矿反应运移模型。由此产生的完全耦合的数值模型将能够1)捕捉与金属动员、运输和沉淀相关的化学和物理过程之间的相互作用，以及2)将金属浓缩所需的时间和空间尺度约束到经济等级。利用这个模型，我们将定量地研究流体盐度、氧化态、pH、金属和硫的有效性、盆地尺度热流、地形、盆地地层、孔隙空间和可渗透流体通道等关键参数对金属矿化动力学的影响。该项目将从简单的通用设置开始，然后陆续增加地质复杂性。地化模型GEMS3可纳入全球回归方法提供的主要成岩元素和矿石元素的内部一致数据库。流体流动模型CSMP++可以包含地球动力学模型提供的对热通量、岩石单元和断层的地质现实约束。我们将主要讨论形成沉积铅锌矿床的一级过程，但该模型将提供更广泛的应用于其他热液系统的潜力。该项目将促进优先方案穹顶的总体目标，以跨学科的方法研究成矿的主要机制，我们提出利用实验和分析数据确定的流体和岩石性质的数值方法，旨在解释铅锌矿床的主要特征。该合作项目是由穹顶方案第一阶段的两个建模项目合并而来的，将具有与研究沉积物托管和其他低温矿藏的项目进一步合作的巨大潜力。

Sediment-hosted ore deposits are major resources for base metals like Zn, Pb, Cu and many other mass and critical metals (e.g. In, Ge, Ga) that are of strategic importance for the transition towards a carbon-neutral society. Ore metal enrichment in basin-scale hydrothermal systems results from a perfect convergence of chemical and physical processes on different temporal and spatial scales, and these systems can only be quantitatively understood by observations and studies beyond the deposit scale. Numerical process models have the potential to identify first-order controls on ore formation and provide physical and chemical constraints on the feasibility and efficiency of hydrothermal systems to generate world-class deposits, which may help guiding future exploration. Major advances in modelling in recent years have either focused on thermodynamic-geochemical fluid-rock interaction or on physical hydrology, while full reactive transport modelling of hydrothermal systems was limited to simplified systems. In the proposed project, we will develop and apply a reactive transport model for ore formation in sedimentary basins, using the geochemical model GEMS3 and the fluid flow model CSMP++. The resulting fully coupled numerical model will be able to 1) capture the interplay between the chemical and physical processes relevant for metal mobilization, transport and precipitation, and 2) constrain the temporal and spatial scales required for metal enrichment to economic grades. With this model, we will quantitatively investigate the respective roles of key parameters like fluid salinity, oxidation state, pH, metal and sulfur availability, basin-scale heat flux, topography, basin strata, pore space and permeable fluid pathways on the dynamics of ore metals enrichment. The project will begin with simple generic settings and then successively increase the geological complexity. The geochemical model GEMS3 can incorporate internally consistent databases for the main rock-forming and ore elements provided by a global-regression approach. The fluid flow model CSMP++ can incorporate geologically realistic constraints on heat flux, rock units and faults provided by a geodynamic model. We will mainly address first-order processes forming sediment-hosted Pb-Zn deposits, but the model will provide much wider potential for applications to other hydrothermal systems. The project will contribute to the overarching goal of the priority programme DOME by addressing key mechanisms of ore formation in a trans-disciplinary approach, where we advance numerical methods that use fluid and rock properties determined by experimental and analytical data and aim at explaining the key features of Pb-Zn deposits. The collaborative project has evolved from the combination of two modelling projects of the first phase of the DOME programme and will have great potential for further collaborations with projects addressing sediment-hosted and other low-temperature ore deposits.