Dr Chris Voisey - “Gold nugget formation from earthquake-induced piezoelectricity in quartz”

The Speaker: 

Chris Voisey completed his Bsc(Hons) degree at the Memorial University of Newfoundland, and his PhD at Monash University. He spent 3 years working in industry as a minerals exploration consultant before returning to Monash as a post doctoral research fellow. His main interest is uniting different disciplines such as geochemistry, materials and nano science to provide a holistic view on deposit formation that can fill in gaps of knowledge that are critical to both academia and industry.  

Abstract: 

Gold nuggets occur predominantly in quartz veins, and the current paradigm posits that gold precipitates from dilute (< 1 mg/kg Au), hot, H2O±CO2-rich fluids due 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. Here, we present a novel concept showing that piezoelectric discharge from quartz can explain the ubiquitous gold-quartz association and the formation of gold nuggets. 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. We confirm experimentally 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 an outstanding 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.

Questions? Please email - senv.gsa@uq.edu.au