MINERALOGICAL SEQUESTRATION OF CRITICAL ELEMENTS IN VOLCANOGENIC MASSIVE SULFIDE DEPOSITS OF THE NORANDA CAMP, QUEBEC

Critical elements are crucial to many industries and to the green energy transition. Due to their polymetallic nature, volcanogenic massive sulfide (VMS) deposits are a potential source for a number of these elements. The Noranda camp in Quebec, Canada, represents one of the best-studied VMS camps in the world and is host to over 20 VMS deposits that were mined in the past. However, little is known on the occurrence of critical elements in these deposits. The current study focuses on seven VMS deposits in the camp, including Ansil, Corbet, Gallen, Horne, Millenbach, Quemont, and Waite Amulet.

Thin sections from these deposits were investigated using automated mineralogy to locate minerals containing critical elements and to determine their relative abundances. Critical elements identified include Te-, Co-, Ni-, Bi-, and Sn minerals. Quantitative data on the abundance of critical element-bearing minerals was used for statistical analysis in ioGAS-64 to explore relative abundances of the different minerals throughout the camp. Tellurium minerals were found in most of the deposits with the exceptions of Gallen and Quemont, though Horne consistently contains comparatively higher amounts and a greater variety of Te minerals, which includes altaite, frohbergite, hessite, rucklidgeite, sylvanite, and volynskite. Cobalt minerals were mainly found at Ansil with minor amounts in Millenbach and Waite Amulet. Nickel minerals were highest in Ansil, while Bi minerals were highest in Ansil and Millenbach with variable amounts in Corbet, Horne, and Waite Amulet. Tin minerals were abundant in Corbet and Millenbach with variable amounts in Ansil, Horne, Quemont, and Waite Amulet. It is noteworthy that Te minerals were found in variable amounts in most of the deposits and that Ansil contains the most variety of critical elements (Co, Ni, Bi and Te).

Scanning electron microscopy revealed that critical element-bearing minerals often occur at grain boundaries between the main sulfide mineral grains or as inclusions within these minerals. This suggests that these critical element-bearing minerals formed during metamorphic recrystallization and remobilization when impurities originally contained in the major ore minerals were expelled from the crystal structure to form new accessory minerals.