Phys.org September 2, 2024
Gold nuggets occur predominantly in quartz veins, and the current paradigm posits that gold precipitates from dilute (<1 mg kg−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. Using quartz deformation experiments and piezoelectric modelling researchers in Australia investigated if piezoelectric discharge from quartz could explain the ubiquitous gold–quartz association and the formation of gold nuggets. They found that stress on quartz crystals could generate enough voltage to electrochemically deposit aqueous gold from solution as well as accumulate gold nanoparticles. Nucleation of gold via piezo-driven reactions was rate-limiting because quartz is an insulator; however, since gold is a conductor, their results showed that existing gold grains were the focus of ongoing growth. They suggested that this mechanism could help explain the creation of large nuggets and the commonly observed highly interconnected gold networks within quartz vein fractures… read more. TECHNICAL ARTICLEÂ
Quartz crystal models depicting the relationship between a CPO (‘texture’) and piezoelectric polarization. Credit: Nature Geoscience, 2 September 2024