North Bullfrog


The North Bullfrog Project consists of leased, patented and unpatented mining claims covering an area of approximately 90.5 km2 consisting of a mix of private mineral leases of patented federal mining claims and 1,134 federal unpatented mining claims.  The project is situated 10 km north of Beatty, Nevada, and 8 km north of the Bullfrog Mine* formerly operated by Barrick Gold Corporation.  The project represents a large, low-sulphidation, epithermal bulk-tonnage gold system hosted in volcanic and sedimentary rocks.

* This information is not indicative of the mineralization on the North Bullfrog property or the potential production from or any future mining of the North Bullfrog property.


The project is 100% controlled by Corvus Gold.

Project Background

Gold was discovered in the Bullfrog district in 1904 resulting in an estimated production of approximately 112,000 ounces of gold and 869,000 ounces of silver through 1921 from high-grade vein systems that remained open along strike and down dip.  There was only minor activity in the district after the initial production period until modern exploration at the North Bullfrog project area started in 1974 and continued until 1996 during which time several companies mapped, sampled, and drilled several areas of gold mineralization.  Declining precious metal prices in the late 1990s resulted in reduced interest in the area.

In 2005, the project was picked up and explored by Redstar Gold Corporation (RGC).  In 2006, International Tower Hill Mines Ltd. (ITH) entered into a joint venture agreement with Redstar to explore the project and subsequently purchased all of the RGC interest in 2009. In the spin out of Corvus Gold Inc. from ITH in August 2010, the 100% interest in the project was transferred to the Company.


Geology and Mineralization

The North Bullfrog project lies along a northerly trending district-scale fault system which extends from the Bullfrog mine into the project area and believed to be a regional control to gold mineralization.  Numerous normal faults cut the volcanic sequence and localized vein-style gold mineralization in both areas.  Basement Paleozoic limestone, shale and quartzite occur in the project area, locally as large rootless inclusions within volcanic debris-flow breccias.  Unlike the Bullfrog mine area, the North Bullfrog contains abundant syn-volcanic intrusions, possibly indicating a more proximal magmatic/volcanic environment compared to the Bullfrog mine.

Two styles of precious metal epithermal mineralization are present at the project: 1) potentially high-grade, structurally controlled fissure veins and associated stockwork zones, and 2) low-grade disseminated or replacement deposits within altered volcanic rocks.

Exploration summary

Drill programs in 2007 and 2008 encountered significant mineralization at three target areas: Mayflower, Sierra Blanca and Pioneer. From the initial results, a multiple deposit concept for the property which could support a central processing facility was developed.

A 75-hole, 17,820-metre drill program was carried out from October 2010 to July 2011.  The program was successful in defining a thick oxide mineralization in the northern portion of the property covering approximately 1.6 kmresulting in an initial resource estimate published in late 2011.  A highlight of the 2010-2011 drill program included a hole that returned 13.7 metres (11.9 metre true width) of 5.9 g/t gold and 5.2 g/t silver, including 6.1 metres grading 11.9 g/t gold and 8.8 g/t silver. 

For 2012, a 2-phase drill program completed 4,000 metres of PQ core drilling and RC drilling to assess the resource expansion potential of the current deposit in step-out holes and to assess the YellowJacket high-grade zone.  A more extensive +20,000 metre second drill program began in May 2013 to follow up on the defined broad zones of bulk tonnage gold mineralization in North Sierra Blanca as well as the high-grade feeder zone at YellowJacket.  In February 2014, a +5,000 metre core drilling program began with all drilling to be conducted at the YellowJacket high-grade zone.  A 12,000 metre RC drill program was completed in December 2015.  The 2015 program tested multiple prospective targets at the peripheral boundaries of the existing known deposits as well as new, never before drilled targets in the Eastern portion of the project.

YellowJacket High-Grade Target

During the 2012 exploration drill program, a core drill hole was positioned in an area to the Northeast of the boundaries of the proposed Sierra Blanca pit called the YellowJacket zone.  It was believed this area could host a high-grade feeder system.  Hole 12-138 intersected 72.4m @ 1.74 g/t gold & 98.7 g/t silver including 4.3m of 20.0 g/t gold and 1,519 g/t silver.  The mineralization found in the hole was a combination of multi-stage banded high-grade gold-silver quartz veins, surrounded by stockworks of single stage quartz and low-grade disseminated mineralization. The zone begins at 40 metres in depth traced to 130 metres and remains open at depth.

The 2013 & 2014 drill program expanded the known system to 800 metres strike with notable drill holes such as 13-344 intersecting 8.3m @ 10.72 g/t gold & 10.45 g/t silver & 14-400 intersecting 35.9m @ 17.1 g/t gold & 19.5 g/t silver.  Of particular note, the silver to gold ratio of this system is higher than the typical 1:1 ratio found throughout the North Bullfrog project.   Following the completion of the 2014 drill campaign at YellowJacket, the Company released an updated resource calculation and preliminary economic assessment (PEA) for the North Bullfrog Project in Q2 2015.  Results of the PEA can be found here: here.

Exploration Targets

The 2016 drill program began early in the year designed to identify additional high-grade vein systems within the project area similar to the newly discovered YellowJacket deposit and to drill around the peripheral boundaries of the proposed pit outline.  

Intial holes of the program intercepted extensive mineralization in a new zone to the North of the Sierra Blanca and YellowJacket deposits in an area called Swale.  Several holes intersected broad zones of +1 g/t gold that were surrounded by thick low-grade zones along north-sout trending structures.  This area, along with the NW boundariers of the Sierra Blanca deposit known as the NWSB zone is prospective for additional mill grade mineralization.  

Drilling also intercepted mineralization at the Liberator Zone, directly east of the YellowJacket deposit.  Hole NB16-303 returned 153.9m @ 0.55 g/t gold & 0.92 g/t silver.  This broad structural zone of mineralization opens up the possibility of another area hosting significant tonnage of mill grade material proximal to the current pit design.  

Phase II of the 2016 drill program began in October and will continue into early 2017 targeting the North end of the YellowJacket deposit, Liberator and Swale zones.

There are several priority targets still yet to be addressed at North Bullfrog.  The Company will look to revisit these targets in potential small scale drill campaigns in the future.