Sulfidanatexis

Metamorphic sulfide melts: characteristic textures as a clue to understand melt migration and precious metal separation

01/06/2024 to 31/05/2027

The proposed research will investigate textures formed by sulfide anatexis of base metal sulfides at high metamorphic conditions. Some of the world's largest Pb-Zn-Ag deposits are of this type (e.g. Broken Hill, Australia) so a better understanding is important from a scientific and economic perspective. To date, there are only a few papers that deal with sulfide anatexis. While some publications write that sulfide anatexis is impossible, others use experiments to show that it is possible or list points on how to detect sulfide anatexis under the microscope. There is no work to date that refers to textures that can be seen in the field or hand specimen. Preliminary studies have shown that these textures are similar to those produced in magmatic sulfide deposits by the interaction of sulfide and silicate melts. These include large silicate crystals found within sulfides. These textures may indicate that large volumes of sulfide melt were present along with silicate melt during metamorphism. Upon cooling, this sulfide melt may crystallize different sulfides and therefore fractionate. If tectonic movement occurs during crystallization, then the fractionated residual melt, enriched in precious metals, could migrate, and therefore remove these precious metals from the ore body. Therefore, (1) textures will be characterized to infer sulfide anatexis and the degree of melting, and (2) possible element mobilization during crystallization and fractionation will be studied to use these findings as an exploration tool or to understand in which part of the deposit the precious metals are enriched.