Cortez Summit Property

Eureka County, Nevada

Carlin Gold's Cortez Summit property is located in the Cortez gold trend. The property consists of 142 100%-owned unpatented lode claims and is located in the midst of an expanding number of gold deposits. The Company's primary target is Carlin-style mineralization in a structural and stratigraphic setting similar to that at the nearby deposits, including the new Goldrush discovery and the operating Cortez Hills mine. The Goldrush resource is hosted primarily in a favorable interval in the Devonian Wenban Formation, a carbonate unit that is also an ore host to other deposits in the Cortez trend. Carbonates of the overlying Horse Canyon Formation are also hosts at Goldrush and in some of the other deposits in the district. The geographical and structural relationships of the mineralized trends are illustrated in Figures 1 and 2. Deepening of a prior reverse circulation hole with core in 2013 established that the sedimentary rock units at Cortez Summit are stratigraphically equivalent to the mineralized host units at the neighboring Goldrush discovery. The presence of favorable mineralized host rock stratigraphy in the vicinity of the important Fourmile structural zone combine with the property's strategic location to make Cortez Summit an excellent exploration target. Exploration potential was further augmented by two new high grade holes at Barrick's "Fourmile" target north of their Goldrush resource and located adjacent to Cortez Summit. Barrick states that these holes have encountered mineralization "well above the average grade of the indicated and inferred resources at Goldrush", for example 14.3 meters(m) grading 31.7 grams per tonne (gpt) and 5.8m grading 49.6 gpt (Barrick Feb. 22, 2016 news release). Barrick's recent Fourmile success represents a different mineralization style than at Goldrush; although still contained in similar lower plate stratigraphic units, it is within the contact metamorphic zone adjacent to the Mill Canyon stock (see Fig. 3). Barrick points out similarities in mineralization style to the Deep Star and Deep Post deposits on the Carlin Trend (Barrick Investor Day webcast presentation, Feb. 22, 2016). Newly encountered high grade mineralization within the contact metamorphic zone is a positive development for the Company because this zone extends on to our property and presents an additional, high grade, target type.

The southwest corner of the Cortez Summit property lies within one mile northeast of Barrick's new Goldrush discovery. As of December 31, 2016, Barrick reported an 11.5 million oz gold resource at Goldrush, containing a measured/indicated resources of 9.6 million tons grading 9.6 grams/ton gold. Barrick has advanced the Goldrush project through the prefeasibility stage, and envisions annual underground production of 450,000 oz at an average all-in-sustaining cost (AISC) of $660/oz. Barrick contemplates a mine life of 21 years with production beginning as early as 2021. The permitting process is scheduled to commence in late 2017 (Barrick news release Feb 22, 2016) and permits to begin construction of the twin exploration decline have been received (Barrick 2016 Q4 webcast). Barrick's Cortez Hills operation (11 MM oz gold pre-production reserve/resource) is located 4 miles west of the property, just north of the permitted exploration decline portal.

Figure 1 - Cortez Trend

Cortez Trend

Figure 2 – Central Cortez Trend Structural Setting

Central Cortez Trend Structural Setting

Carlin Gold identified the area as prospective and staked initial claims in 2007, prior to Barrick's initial September 2011 announcement of the Goldrush discovery. The company was encouraged by initial rock sample geochemistry results from silicified and iron-stained siltstones from the NNW trending Fourmile structural zone on the west edge of the property. Grab samples collected from this area contained up to 0.447 gpt gold and 307 ppm arsenic (Figures 4, 5).

Two types of mineralizing systems exist on or adjacent to the Cortez Summit property:

1) Carlin-style sediment-hosted gold. The adjacent Carlin-style deposits (Goldrush, Cortez Hills, Horse Canyon) contain typical structural and stratigraphic controls that characterize Carlin-type deposits in north-central Nevada. These deposits are probably late Eocene (±40 Ma) in age. Most Carlin-style mineralization occurs in the favorable carbonate section that constitutes the 'lower plate' of the Roberts Mountain thrust fault system. This is the primary target at Cortez Summit.

2) Buckhorn-style volcanic-hosted low sulfidation Au-Ag. This style of mineralization is associated with an extensive Miocene epithermal system (14.6 Ma) which is controlled by NNW-trending Northern Nevada rift structures. Nearby examples are Klondex's operating Fire Creek mine.

Except for a narrow sliver of Paleozoic 'Upper Plate' siliciclastic rocks of the Ordovician Vinini Formation poorly exposed on the west edge of the property, the Cortez Summit property is covered by Miocene-age basalts and gravels which postdate the Carlin-style mineralization event. On the west side of the property, the Vinini Formation is unconformably overlain by a Tertiary volcano-sedimentary sequence consisting of a lower gravel unit and an upper series of Miocene (15-16 Ma) basaltic andesite flows. Drilling by Carlin Gold indicates that the Miocene sequence varies in thickness from zero on the southwest side of the property to >500 ft. (150 m) in the south central portion. The Buckhorn deposits are primarily hosted by basaltic andesite in this sequence. Dikes, plugs and minor flows of Miocene (15 Ma) rhyolite locally intrude and overlie the gravel and basaltic andesite units, including the rhyolite plug exposed in the southwest corner of the property (Figure 4, geology map).

Two intrusive phases are recognized just west of the property including: 1) Jurassic-age quartz monzonite of the Mill Canyon pluton; and 2) probable Tertiary-age quartz porphyry dikes and small intrusive bodies. These quartz porphyry intrusions may be correlative with early Oligocene quartz porphyry dikes which are common at the Horse Canyon, Cortez Hills and other Cortez district deposits.

Two structural orientations dominate the Cortez Summit area: 1) NNW horst and graben structures that define the Northern Nevada Rift structural trend and control mineralization along the Aspen and Buckhorn mineralized trends, and 2) less well-defined NE-trending structures exhibited by the drainage patterns eroding the basaltic andesite (ie. Willow Creek structure). The Northern Nevada Rift structures associated with Buckhorn-style mineralization potentially represent shallow manifestations of the deep-seated feeder structures involved in older Carlin-style mineralization at depth. A good example of this is the prominent NNW trending Fourmile structural zone that trends for 4,500 feet (1370 m) along the west side of the property and appears to be associated with Carlin-style alteration and geochemistry. In fact Barrick has mapped alteration in upper plate units along the northern extension of the Fourmile structural zone off Cortez Summit and down Fourmile Canyon to the Crescent Valley range front, a distance of approximately 4 miles (6.4 km). The Miocene rhyolite plug of upper Willow Creek in the southwest corner of the property intrudes the inferred structural intersection between the NE-trending Willow Creek structure and the NNW-trending Fourmile structural zone.

In August 2012 a reverse circulation drill program was initiated to establish the presence and depth of the favorable Lower Plate carbonate section on the west side of the property, in proximity to the Fourmile structural zone in the southwest portion of the property. Most of this target area is covered by post-mineral gravel and basaltic andesite. Where Paleozoic rocks are exposed on the west edge of the property, sampling along the Fourmile structural zone has yielded gold values of 0.447 and 0.263 gpt in altered siliciclastic rocks. Rock sampling along a drill road cut yielded 0.175 gpt gold over 50 feet (15 m) in altered siltstones (Figs 4, 5).

Figure 3 – Barrick's Fourmile Target

Barricks Fourmile Target

Figure 4 - Cortez Summit Geology Map – Southwest

Cortez Summit Geology Map – Southwest

7 reverse circulation drill holes were completed in 2012 to depths ranging between 1500 and 1800 feet (457-549 m), for a total of 11,720 feet (3,573 m). All holes encountered Paleozoic sedimentary rocks. One hole was collared in the Paleozoic rocks and the remainder were drilled into Paleozoic rocks beneath younger Miocene basalts and gravels. Paleozoic lithologies include grey-black siltstone, with lesser sandstone and chert. CS12-7 penetrated and bottomed in a 300 foot interval containing variably laminated calcareous siltstones.

Anomalous gold with Carlin-type pathfinder elements are present in six of the seven holes drilled in 2012. The following table shows significant gold values (≥ 0.100 gpt Au) encountered in the drill program.








brown sandstone with calcite veinlets




black siltstone with pyrite and calcite veinlets




Rhyolite intrusive, weakly silicified




limonitic sandstone and siltstone




quartz-sericite-pyrite altered siltstone




silicified siltstone/sandstone




Intermediate to mafic intrusive




Gravel/fault scarp breccia various clast types




Strongly Silicified siltstone/sandstone




gray silicified siltstone

Anomalous arsenic zones (>100 ppm) range up to 115 feet (35 m) in drilled thickness and contain values up to 1,530 ppm arsenic, 70 ppm antimony, 3 ppm thallium and 1.8 ppm mercury. Two holes with the longest anomalous arsenic intervals were drilled 1,900 feet (580 m) apart on the west side of the property, and are located in close proximity to the Fourmile structural zone. These intervals occur in the upper plate strata above the lower plate Horse Canyon and Wenban formations encountered in the drilling described below.

In September 2013 the Company re-entered vertical reverse circulation hole CS12-2 and deepened it from 1,760 ft. (537 m) to 4,032 ft. (1,229 m). Short intervals of anomalous gold values to 0.667 grams/tonne and Carlin-type pathfinder elements were encountered in hole CS12-2C, as well as longer intervals of anomalous arsenic values (>100 ppm) ranging up to 85 ft. (25 m) of drilled thickness. The bottom 900 feet (274 m) consisted of variably calcareous mudstone/sandstone, and silty/sandy, laminated, variably carbonaceous limestone, interpreted to be lower plate strata of the Horse Canyon and Wenban formations. This material locally displays Carlin-type alteration features such as decalcification, clay alteration and calcite veining. Carlin geologists are encouraged that favorable lower plate carbonate rocks are present near the projection of the gold-bearing Fourmile structural corridor, at depths consistent with some of the holes in the north portion of Barrick's neighboring Goldrush discovery and their new Fourmile target.

In an effort to further enhance the understanding of the encouraging geology encountered in hole CS12-2C, the Company engaged the services of Dr. Harry Cook, President/CEO of Carbonate Geology LLC. Dr. Cook is very familiar with the Cortez District and Barrick has acknowledged his important role in developing an understanding of the gold-hosting Paleozoic stratigraphy in the area, including the neighboring Goldrush discovery. Dr. Cook examined the lower 984.5 feet (300 m) of hole CS12-2C, which resulted in his interpreting the bottom 650 feet (198 m) of the hole to contain Devonian strata. The base of the Roberts Mountain Thrust Fault is interpreted at a hole depth of 3,382 feet (1,031 m). Dr. Cook states that "Core CS12-2C strata are comprised of very favorable gold-host rocks within both the Wenban Formation and Horse Canyon Formation. These strata are coeval with the nearby Wenban Fm. And Horse Canyon Fm. carbonate gold-host strata that comprise the gold hosts in Barrick's Goldrush discovery." The lower plate strata are comprised of carbonate debris flows, turbidites, slides, slumps and lime and quartz siltstones and mudstones. The geological setting represents an optimal depositional environment for Carlin-type gold deposits. Dr. Cook's interpretations are based on fossil and sedimentologic evidence in addition to his extensive field, pit and core experience at many locations and mine sites throughout Nevada. Further drilling is warranted, according to Dr. Cook.

The strategic location of the project, along with the similarity in geologic setting to the neighboring Carlin-style deposits, makes Cortez Summit a high quality target for Carlin-style gold mineralization. Only a small portion of the property has been evaluated, and the Fourmile structural corridor in particular requires more attention. The Company expanded the permit area in 2013.