GOLD DEPOSIT TYPES FOR THE GREAT BASIN OVERVIEW
Overview of the Gold Deposit Types for the Great Basin
To put the Great Basin gold endowment into context we should examine global endowment.
The important deposit types are virtually overshadowed by paleoplacers, predominantly from the Witwatersrand in South Africa. These unique deposits are diminishing rapidly in global importance so are not a deposit type to consider within a discussion of Great Basin gold occurrences.
Globally, the Copper - Gold Porphyry deposit types are very large producers. Examples in the Great Basin include the Robinson and Yerington mines. The most significant deposit in the Great Basin is Bingham Canyon located in central Utah on the eastern edge of the Great Basin. This mine produces about 275,000 tons of refined Cu, 400,000 oz Au, 4 million oz Ag, and 25 million pounds of Mo each year. Historically production is over 18 million tons of Cu and 26 million oz of Au.
The Great Basin has been dominated by Carlin type gold deposits and Epithermal gold deposits. Carlin types are the major producer in Nevada and are becoming increasingly important worldwide. These deposits can transition up to the near surface epithermal environment producing deposits which are becoming more abundant on a global scale. Epithermal deposits tend to be much smaller, but there are notable exceptions such as the 20 million oz Round Mountain Mine in central Nevada. Volcanic-hosted epithermal deposits are often high-grade, profitable mines. Renaissance's Bunce, Sinter and Fireball properties are examples of this type of deposit.
Skarns can be linked to intrusion-related deposits as they occur proximal to intrusions in Nevada and simply represent the interaction of hydrothermal fluids with limestone creating a specific type of mineralogy. The Golden Shears Project, located in southern Nevada, is a good example of the relationship with exposed porphyries and skarn mineralization.
Both skarns and intrusion-related deposits are found in Nevada. Recently a new classification, reduced-intrusion gold, originally defined in Alaska, is now being recognized globally including in the Great Basin. The large Bald Mountain Mine was for years classified as Carlin type, but is now being shown to host a reduced intrusion system. Renaissance is pursuing these types of deposits, as they have been underexplored in Nevada and provide an opportunity for great success. Buffalo Canyon-Everson Deposit in Nye County, Nevada is the best example of this in our current portfolio.
The largest global gold endowment in the world occurs in Orogenic deposit types. These are formed simply by the sweating of gold from rocks squeezed during the process of mountain building (orogeny). Little exploration in Nevada has been focused on these deposits, but there are examples of very large historic mines. Again, Renaissance has been pursuing these less explored deposits within select areas of Nevada.
VMS, IOCG, PGE-related and Paleoplacer deposit types either do not occur or are insignificant in their occurrence in the Great Basin.
More detailed descriptions of each deposit type are found under their specific headings.