Blackhawk Porphyry and Epithermal Copper/Gold Projects
The Blackhawk Project is located within the Excelsior Mountain Range, Mineral County, Nevada. The Blackhawk Project is accessed via paved state highway 95 and is 40 minutes’ drive from the regional hub of Hawthorne. Local access to the project is gained by an all-weather county gravel road via the abandoned mining township of Marietta. The Blackhawk Project consists of 636 contiguous 20-acre claims covering 49km2 and is close to existing highways and extensive infrastructure.
Sierra Nevada has identified two major and extensive components of a large mineralised system at its Blackhawk Project – an epithermal component and a porphyry component. The Blackhawk epithermal vein system is prospective for high grade, structurally controlled Ag-Au and base metal deposits and is partially coincident with and adjacent to the northern edge of the Blackhawk porphyry-style alteration and mineralisation. At least eight historic mining areas were operated in the Blackhawk epithermal vein system between the 1860s and the early 1900s, the main mining areas being around the Endowment, Morning Star and Blackhawk mines. The epithermal vein system covers an area of approximately 5km2 and contains up to 22-line kilometres of mostly untested veins. Sierra Nevada has obtained bonanza grade precious and base metal rock chips from the epithermal vein system and has a suite of drill ready targets.
The porphyry system is defined by a world class scale, fertile alteration system more than 30km2 in size. Centrally the porphyry system is marked by a 4km diameter ring of historic mines that have exploited various porphyry style mineralisation types which is, in turn located coincident with a large 13km2 zone of high chargeability (sulphides) defined by IP geophysics. The porphyry system is regarded as having significant potential to host world-class porphyry-related Cu-Au mineralisation.
Favourably located in southern Nevada, the Blackhawk Project occurs within the prolific Walker Lane Trend, which is a Tier-1 mineral province that hosts numerous world class gold, copper, and silver deposits. The Walker Lane Trend is defined as the boundary between the Great Basin Extensional Province to the north and the Sierra Nevada Block to the south. It is a zone of dextral strike-slip/transtensional deformation and merges with the Southern California Shear Zone to the southeast. The Walker Lane Trend contains the giant Round Mountain deposit (20Moz gold which is owned and operated by Kinross Gold), the legendary Comstock Lode (8.5Moz gold and 200Moz silver, which has been mined by multiple parties), the Yerington Porphyry deposits (over 4Mt copper in production and Reserves relating to multiple parties); the Candelaria deposit (230Moz silver of previous production and current Resources, which currently owned by Silver Standard and is 25km along trend to the southeast of the Blackhawk Project); and various other multi-million ounce gold deposits. The estimated production and Reserve endowment of the Walker Lane Trend is at least 50Moz of gold, 700Moz of silver, 4Mt of copper.
SNX completed the first diamond core hole (SNX001D) since listing on the ASX at its Blackhawk porphyry project to a total depth of 1196.98m. This brings the total number of core holes drilled into the project to 3. SNX planned the hole to test depth extensions of previously mined high-grade precious and base metal veins, and the northern limits of a large and vertically attenuated chargeability anomaly. It also aimed to test a well-defined zone of high resistivity interpreted as a potential zone of alteration and/or intrusion. SNX extended the hole beyond the planned depth of 800m to a total depth of 1196.98m, due to encountering encouraging porphyry style alteration with elevated copper and molybdenum through to end of hole.
A prominent feature of SNX001D was the presence of large and sometimes intense zones of faulting reflecting the potential for large block movements and fluid pathways including preferential alteration development.
SNX001D provides Sierra Nevada Gold with multiple vectors for future targeting of the porphyry system. Encouragingly the presence of well-defined inner propylitic to local potassic alteration and “B” style veining is considered both important and favourable vectors to porphyry mineralisation.