The Keystone-Jumbo project area is located ~4 km southeast of the Goldwedge deposit and mill, and along strike of the regionally significant N30W trending Reliance fault zone, which trends through Goldwedge and the Manhattan Mine East and West pits. Geologically, the Keystone and Jumbo deposits occur near the northern margin of a Cretaceous granite intrusion within limestones, argillites, quartzites and schists of the Ordovician Palmetto-Vinini Formation. Mineralization is controlled by high-angle N30W faults transected by a weaker N30E and N80E structural fabric. Intersections of these fabrics control the high-grade gold mineralization in the historic Keystone and Jumbo pits.
The gold itself is localized within fault breccias and silicified metasediments in the Keystone and Jumbo pits as well as oxidized quartz-pyrite-gold veinlet stockworks in the clay alteration halos surrounding the core of the known mineralization. Hydrothermal alteration/mineralization affects the Mesozoic granites and some low-volume younger volcanics, suggesting that the age of the gold bearing system is mid to lateTertiary and may be genetically related to the Round Mountain-Toquima caldera complex.
Limited historic surface drilling at Keystone reported substantial downhole widths and grades, leading Nevada Goldfields to undertake a small open pit excavation in 1990 that recovered 5,750 ounces of gold. A preliminary review of the available data indicates that significant drill intercepts lie below and to the southeast of the open pit. A small open pit was also excavated around the same time on the Jumbo deposit. New Concept Mining reported mineral resource estimates for both the Jumbo and Keystone deposits in May 1997; however, neither estimate is compliant with NI 43-101 and await verification.
2019 Exploration Drilling Program
Scorpio Gold commenced an exploration diamond drilling program in the Keystone-Jumbo area in June 2019. The program calls for drilling of up to 29 exploration holes with the intention of building on historic drilling and previously reported surface sampling results (see 2016 program below and December 15, 2016 news release).
2016 Exploration Program
Scorpio Gold initiated a three-phased soil sampling program and ground magnetic/VLF electromagnetic survey over the Keystone-Jumbo project area in mid-2016. The geophysical survey was designed to assist in structural interpretation of the area and the soil sampling program to detect anomalous gold mineralization in areas covered by overburden. In the Keystone-Jumbo area, overburden covers approximately 85% of the land position and typically ranges from 0 to 2 meters depth.
Phase 1 of the soil sampling program was conducted over the main area of interest that surrounds the historic Keystone and Jumbo mine workings. Results outlined a 1,100 meter long soil anomaly that follows a distinct N30-45W trending structural break (see November 14, 2016 news release). This trend sub-parallels the N30W structure mapped in the Keystone pit, which is determined to be the main structural control to mineralization.
Phases 2 and 3 of the sampling program covered the remainder of the Keystone-Jumbo project area that was not subjected to ground disturbance during historical mining operations. Results have extended the soil anomaly's strike length 130 meters to the southeast, outlining a 1,230 meter mineralized trend that crosses nearly the entire NW length of the Keystone Jumbo land holdings (see December 15, 2016 news release).
Results from this soil sample program correlate well with the interpreted structural geology from the field mapping and the ground magnetic/VLF electromagnetic geophysical surveys recently processed. Of note is the spatial association of high-grade soil samples from all 3 phases with the granite-metasediment contact, especially where favorable structural orientations are found. This lithological contact is considered a promising exploration target in addition to the multiple NW trending structures recognized in the area.