Enrichment of precious metals associated with chalcopyrite inclusions in sphalerite and pyrite

Abstract

The results of investigations into enrichment of precious metals in sphalerite and pyrite from the Maluntou epithermal gold deposit, China are reported. The resulting data suggest intimate associations of Au-and Ag-bearing nanoparticles with chalcopyrite inclusions in sphalerite and pyrite. The origins of chalcopyrite inclusions involved different hydrothermal processes, including recrystallization-driven phase separation from parent chalcopyrite-sphalerite solid-solutions, and replacement of pre-existing pyrite in the presence of Cu-bearing fluids. The chalcopyrite blebs/lamellae follow sphalerite {111} planes which define a shared sulfur layer for both chalcopyrite and sphalerite. This study indicates that mixing and boiling during evolution of ore-forming fluids for the Maluntou deposit are key processes for the abnormal enrichment of precious metals in sphalerite and pyrite. The chalcopyrite micro/nano inclusions enhanced enrichment of precious metals in sphalerite provides new insights into the controls on the enrichment of precious metals in sulfides.

Metal Preservation and Mobilization in Sediments at the TAG Hydrothermal Field, Mid‐Atlantic Ridge

“… SEM microphotography. (a) Detrital barite grain from Unit M3 of Southern mound (22RD, 150 cm depth); (b) Zoom‐in onto the chalcopyrite dissolution pitting; (c) few hundred μm long chalcopyrite grains with indications of partial dissolution pitting from the Mir Zone fan (d) few tens of μm long aggregate of fine grained cubic pyrite (Py), partially dissolved chalcopyrite (Cp) and Cu‐rich sphalerite (Sph) presenting octahedron faces and likely chalcopyrite disease (Barton & Bethke, 1987) from a thin sulfide layer in the depositional channel. …”