INTRUSION RELATED GOLD DEPOSITS OVERVIEW
Intrusion Related Gold Deposits
This is a series of deposit types that are genetically and spatially related to intrusions. These can manifest themselves in many different ways. In a sense, Carlin type deposits are intrusion related as they are distal manifestations of Eocene aged intrusive complexes in Nevada. Within this intrusion classification they are more proximal and can often be hosted by the intrusion itself. The chemical zonation within these deposits allow geologists to target ore bodies based on rock chip and soil geochemistry.
The figure below is from the SEG Newsletter Lang et. al. 2000.
One of the best studied systems is the Fort Knox Mine in Alaska which has a resource of over 10 M ounces; the largest is Muruntau in Uzbekistan with a reported gold resource of over 170 M ounces.
In Nevada there are many intrusion related precious metal systems. A classic example is the McCoy Mine that has gold directly related to the intrusion and in areas where the hydrothermal fluids are hosted by carbonates may form "skarn" mineralization characterized by calc-silicate mineralogy and associated gold and silver.
Renaissance believes our Fourth of July Project is an intrusion related deposit due to the presence of a large geochemical halo with Mo, W and other elements. To the south the nearby Spring Valley deposit, reported as an expanding 5 M ounce resource, the ore clings tightly to the intrusion, indicating the likelihood that this is also intrusion related.
Our Buffalo Canyon Project, which includes the Everson deposit, is a reduced intrusion type gold system with 350,000 non-compliant ounces and the potential to expand in all directions. Good gold recoveries in the sulfide and oxide ore and the ability to map the mineralized pyrrhotite halo by geophysics provide advantages to both exploration and production.
A good analogue to our Buffalo Canyon Project is the Bald Mountain Mine owned by Barrick and containing over 7 M ounces Au. For many years this was a low grade, near surface open pit, but when drilling intersected the top of the intrusion, an ore body with a high grade 1 opt Au core was discovered.