Origin of magnetite from the Volcanogenic Massive Sulfide deposits of the Matagami Mining Camp, Abitibi, Canada: implications for exploration

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Volcanogenic massive sulfide (VMS) deposits are exploited primarily for Zinc (from the sulfide mineral,sphalerite - ZnS) and Copper (from the sulfide mineral, chalcopyrite - CuFeS2). VMS deposits formed fromhot, hydrothermal fluids circulating through volcanic rocks on ancient seafloor (similar to black smokers on theseafloor today). However, some VMS deposits contain unusually high amounts of the mineral magnetite(Fe3O4), rendering significant parts of the deposits uneconomic. Magnetite is thought to form by replacementof the sulfides. However, the detailed mechanism/s of this replacement process, and why the replacement of theentire deposit is nearly complete, in some cases, are not well understood. Therefore the Company-specificproblem is to understand better the origin of massive magnetite in their VMS deposits at Matagami, Quebec.To address this scientific problem, the proposed project aims to provide new constraints on the formation ofmagnetite in VMS deposits through a combined study of the petrography and trace element chemistry ofmagnetite and sulfides from Matagami VMS deposits. We will use the innovative technique of laser ablationICP-MS to obtain high quality, in-situ trace element data. This is a rapidly expanding field of research withinMineral Deposit studies. The expected outcomes of the project will lead to 1) a better understanding of thereplacement process/es and timing of magnetite formation and 2) identification of the type of hydrothermalfluids involved and their possible relation to new style of mineralization in the Mining Camp. The current (andlast) operating mine of Matagami is owned by the Company and will last only a few years, making explorationfor the next mine critical for this northern mining town. Being able to better understand the role of themagnetite in the VMS deposits of Matagami will help better define exploration criteria that will contribute tofinding new exploration targets. A number of other VMS deposits in Eastern Canada contain similar massivepods of magnetite, and thus the results of this study are directly applicable and beneficial to othermining/exploration companies in Canada.