Fluid-Enhanced Coarsening of Mineral Microstructures in Hydrothermally Synthesized Bornite–Digenite Solid Solution

Symplectic microstructures are abundant in copper–iron–sulfide minerals and are conventionally considered to form by solid-state diffusion processes. Here we experimentally demonstrate that coarsening of exsolution lamellae occurs ∼1000 times faster in the presence of a fluid compared to the equivalent dry system. Bornite–digenite solid solutions (Cu5FeS4–Cu8.52Fe0.11S4.88) were synthesized hydrothermally via the replacement of chalcopyrite, and...