澳大利亚莫纳什大学Voisey, Christopher R.及其课题组近日取得一项新成果。他们发现石英中地震诱发的压电性促进金块形成。相关论文于2024年9月2日发表于国际顶尖学术期刊《自然—地球科学》杂志上。
据了解，金块主要出现在石英矿脉中，目前的范例认为，由于温度、压力和/或流体化学的变化，黄金从稀的(金<1mgkg-1)，热的，富含二氧化碳的水流体中沉淀出来。然而，大块金块的广泛存在与这些流体的稀释性质和石英的化学惰性不一致。石英是地球上唯一丰富的压电矿物，驱动造山型金矿床形成的地震活动的周期性意味着，矿脉中的石英晶体将经历数千次偏应力。
研究人员使用石英变形实验和压电模拟来探讨，石英的压电放电是否可以解释普遍存在的金-石英共生现象和金块的形成。研究发现，石英晶体上的应力可以产生足够的电压，使溶液中的水基金电化学沉积，并积累纳米金颗粒。通过压电驱动反应形成金的成核是有速率限制的，然而，由于金是一种导体，现有的金颗粒是持续增长的焦点。研究人员认为，这一机制可以帮助解释大块金以及石英脉裂隙中普遍观察到的高度互连金网络的形成。
附：英文原文
Title: Gold nugget formation from earthquake-induced piezoelectricity in quartz
Author: Voisey, Christopher R., Hunter, Nicholas J. R., Tomkins, Andrew G., Brugger, Jol, Liu, Weihua, Liu, Yang, Luzin, Vladimir
Issue&Volume: 2024-09-02
Abstract: Gold nuggets occur predominantly in quartz veins, and the current paradigm posits that gold precipitates from dilute (<1mgkg-1 gold), hot, water±carbon dioxide-rich fluids owing to changes in temperature, pressure and/or fluid chemistry. However, the widespread occurrence of large gold nuggets is at odds with the dilute nature of these fluids and the chemical inertness of quartz. Quartz is the only abundant piezoelectric mineral on Earth, and the cyclical nature of earthquake activity that drives orogenic gold deposit formation means that quartz crystals in veins will experience thousands of episodes of deviatoric stress. Here we use quartz deformation experiments and piezoelectric modelling to investigate whether piezoelectric discharge from quartz can explain the ubiquitous gold–quartz association and the formation of gold nuggets. We find that stress on quartz crystals can generate enough voltage to electrochemically deposit aqueous gold from solution as well as accumulate gold nanoparticles. Nucleation of gold via piezo-driven reactions is rate-limiting because quartz is an insulator; however, since gold is a conductor, our results show that existing gold grains are the focus of ongoing growth. We suggest this mechanism can help explain the creation of large nuggets and the commonly observed highly interconnected gold networks within quartz vein fractures.
DOI: 10.1038/s41561-024-01514-1
Source: https://www.nature.com/articles/s41561-024-01514-1