Xing Yanlu, Brugger Joël, Etschmann Barbara, Tomkins Andrew G, Frierdich Andrew J, Fang Xiya
School of Earth, Atmosphere and Environment, Monash University, Melbourne, VIC, Australia.
School of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN, USA.
Nat Commun. 2021 Mar 2;12(1):1388. doi: 10.1038/s41467-021-21684-5.
Reaction-induced porosity is a key factor enabling protracted fluid-rock interactions in the Earth's crust, promoting large-scale mineralogical changes during diagenesis, metamorphism, and ore formation. Here, we show experimentally that the presence of trace amounts of dissolved cerium increases the porosity of hematite (FeO) formed via fluid-induced, redox-independent replacement of magnetite (FeO), thereby increasing the efficiency of coupled magnetite replacement, fluid flow, and element mass transfer. Cerium acts as a catalyst affecting the nucleation and growth of hematite by modifying the Fe(aq)/Fe(aq) ratio at the reaction interface. Our results demonstrate that trace elements can enhance fluid-mediated mineral replacement reactions, ultimately controlling the kinetics, texture, and composition of fluid-mineral systems. Applied to some of the world's most valuable orebodies, these results provide new insights into how early formation of extensive magnetite alteration may have preconditioned these ore systems for later enhanced metal accumulation, contributing to their sizes and metal endowment.
反应诱导孔隙率是使地壳中流体与岩石能够长期相互作用的关键因素，在成岩作用、变质作用和矿石形成过程中促进大规模的矿物学变化。在此，我们通过实验表明，痕量溶解铈的存在增加了通过流体诱导、与氧化还原无关的方式替代磁铁矿（Fe₃O₄）形成的赤铁矿（Fe₂O₃）的孔隙率，从而提高了磁铁矿替代、流体流动和元素质量转移耦合过程的效率。铈作为一种催化剂，通过改变反应界面处的Fe²⁺(aq)/Fe³⁺(aq) 比率来影响赤铁矿的成核和生长。我们的结果表明，微量元素可以增强流体介导的矿物替代反应，最终控制流体 - 矿物系统的动力学、结构和组成。将这些结果应用于世界上一些最有价值的矿体，为广泛的磁铁矿蚀变早期形成如何可能为这些矿石系统后期增强金属聚集创造前提条件提供了新的见解，这有助于解释它们的规模和金属储量。
