Transport and deposition of metallic nanoparticles and the origin of bonanza epithermal ores

Two principal textures exhibited by metallic ore minerals indicate deposition of metallic nanoparticles during bonanza epithermal ore formation in USA and Japan. These include: 1) 3-dimensional self-organized fractal dendrites that apparently formed by aggregation of metallic nanoparticles under chaotic conditions; and 2) evidence of physical transport and deposition of nanoparticles ("sluice box textures") caused by perturbations along vein walls. To date we have recognized such fractal dendritic nanoparticles aggregates composed of electrum, "naumannite" (various Ag-Se-S phases), and mixed chalcopyrite and naumannite. Naumannite commonly exhibits the transport textures. Previously, nucleation of nanoparticles in these bonanza epithermal ores was interpreted by us to have formed in response to boiling in the shallow epithermal setting. However, new Pb-, Re-Os-, and Cu-isotope data indicate that all three of the aforementioned mineral phases have isotopic signatures consistent with a deep and primitive magmatic source. This implies nanoparticles must have formed deep in the "porphyry to epithermal" environment and then have been transported up to their point of deposition in the epithermal setting.