Sudbury Basin
Operation Overview
The Sudbury Basin is a 60 km by 30 km elliptical geologic structure located just north of the City of Greater Sudbury and approximately 400 km north of Toronto, Ontario, Canada. The Sudbury Basin structure is the result of a meteorite impact, which struck the earth approximately 1.85 billion years ago. The meteorite impact created a crater penetrating the earth's crust down to the magma, which resulted in the introduction of a molten igneous melt sheet, known as the Sudbury Igneous Complex ("SIC"), into the meteorite crater. The meteorite impact also shattered the rocks surrounding the crater thereby creating brecciated and fragmented rock units. The original meteorite impact crater was probably more than 150 km in diameter, but erosion has exposed the smaller, lower portion of the crater and tectonic deformation and thrusting has deformed the original circular shape into its current elliptical form.
Sulphide minerals containing copper, nickel, cobalt and precious metals were introduced into the Sudbury Basin with the igneous melt. The heavier sulphide minerals settled to the base of the SIC and accumulated in the topographic irregularities, such as valleys and dips. The sulphide deposits located at the base of the SIC were rich in nickel, copper, cobalt and contained minor precious metals. Collectively, these types of deposits are called Contact Deposits and were the first type of mineral deposit exploited in Sudbury. They continue to be mined to the present day.
In addition, the meteorite caused major fractures, which radiated out from the Sudbury Basin structure. These fracture systems or dykes filled with igneous melt materials and sulphide mineralization. The radial fracture structures are referred to as Offset Dykes, because they tend to pinch and swell and be abruptly faulted or offset by crosscutting structures. These areas of pinching or faulting are where the sulphide mineralization accumulated as copper-nickel-precious metal Offset Deposits, such as the prolific Copper Cliff Offset deposits and the Company's new Victoria Offsite Discovery.
Approximately 30 years ago, it was discovered that the Contact Deposits were originally enriched in copper and precious metals, however over geologic time these minerals become mobilized and migrated into the shattered host rock ("Footwall") located around the crater and below the SIC. The sulphide mineralization moved through the Footwall breccia until it encountered a structural or chemical trap where it accumulated as high grade, sharp walled Footwall Deposits, such as Vale Inco's 153 Deposit or Quadra FNX's Levack Footwall Deposit ("LFD"), discovered in 2005 and commencing production in 2010.
There is strong evidence that further below the Footwall Deposits, the base metal content of the Footwall mineralization appears to decline or become more erratic, while the precious metal content increases up to the multi-ounce per ton grade. While further exploration work is required to confirm the theory, there is the potential in the Sudbury Basin for Footwall precious metal deposits to be delineated and mined in the future, for example the Lower Levack Footwall Deposit located below the LFD.