Hyperenrichment of gold in pyrite induced by solid-state transportation
Haiyang Xian, Hongping He, Jianxi Zhu, Kunfeng Qiu, Yang Li, Yiping Yang, Jieqi Xing, Wei Tan, A. Tsuchiyama, Masahiro Yastake, Satomi Enju, Akira Miyake, Runliang Zhu
Abstract
Abstract The hyperenrichment of gold is critical for the formation of high-grade gold deposits in orogenic systems, where gold enrichment can reach several percent. However, many details on the nature of the hyperenrichment mechanism remain unclear. Here we show a “self-purification” model that could explain the hyperenrichment of gold from nanoparticles to veinlets in deformed pyrite. The three-dimensional spatial relationship and coexistence of gold nanoparticles and veinlets indicate a direct transformation from the former to the latter in solid-state. Theoretical evaluation reveals that this transformation involves a thermodynamically favorable self-purification process. We thus propose that deformation/thermo drives the transport of gold nanoparticles towards veinlets in pyrite through atomic diffusion. This deformation/thermo-driven model is applicable to any deformed nano-gold-bearing pyrite and explains how solid-state transport can effectively concentrate gold to a very high grade. Similar mechanisms may have broad implications in both ore-forming and beneficiation processes.