Eskay Creek Geology
As the Eskay Creek Mine was a VMS Deposit, which typically forms in clusters, there are good reasons to believe that Eskay Creek was only a small portion of the original deposit. Originally, the Eskay Creek ore body was formed in the ocean. Interestingly, similar ore bodies, rich in Gold and Silver, are currently being formed on the ocean floor, just off the coasts of British Columbia, Oregon & Washington State. As British Columbia was uplifted by Geological Forces, it’s suspected that the Eskay Creek Mine was separated from the main body of Gold and Silver ore, as the Rocky Mountains were lifted high and dry above the Pacific Ocean. The task at hand for the Golden Triangle explorers in the summer of 2010 is searching for the remaining segments of the original deposit, geologists believe to exist.
Abstract from the GSC on VMS Deposits
Volcanogenic massive sulphide (VMS) deposits, also known as volcanic-associated, volcanic-hosted, and volcanosedimentary- hosted massive sulphide deposits, are major sources of Zn, Cu, Pb, Ag, and Au, and significant sources for Co, Sn, Se, Mn, Cd, In, Bi, Te, Ga, and Ge. They typically occur as lenses of polymetallic massive sulphide that form at or near the seafloor in submarine volcanic environments, and are classified according to base metal content, gold content, or host-rock lithology. There are close to 350 known VMS deposits in Canada and over 800 known worldwide. Historically, they account for 27% of Canada’s Cu production, 49% of its Zn, 20% of its Pb, 40% of its Ag, and 3% of its Au. They are discovered in submarine volcanic terranes that range in age from 3.4 Ga to actively forming deposits in modern seafloor environments. The most common feature among all types of VMS deposits is that they are formed in extensional tectonic settings, including both oceanic seafloor spreading and arc environments. Most ancient VMS deposits that are still preserved in the geological record formed mainly in oceanic and continental nascent-arc, riftedarc, and back-arc settings. Primitive bimodal mafic volcanic-dominated oceanic rifted arc and bimodal felsic-dominated siliciclastic continental back-arc terranes contain some of the world’s most economically important VMS districts. Most, but not all, significant VMS mining districts are defined by deposit clusters formed within rifts or calderas. Their clustering is further attributed to a common heat source that triggers large-scale subseafloor fluid convection systems. These subvolcanic intrusions may also supply metals to the VMS hydrothermal systems through magmatic devolatilization. As a result of large-scale fluid flow, VMS mining districts are commonly characterized by extensive semi-conformable zones of hydrothermal alteration that intensifies into zones of discordant alteration in the immediate footwall and hanging wall of individual deposits. VMS camps can be further characterized by the presence of thin, but areally extensive, units of ferruginous chemical sediment formed from exhalation of fluids and distribution of hydrothermal particulates.
