Poker Brown Gold, Nevada
The target at Poker Brown is a large, bulk tonnage, heap leachable gold deposit.
- Strong and extensive (600 x 1,200 m) gold/alteration zone on surface, open in three directions.
- Peñasquito, Camino Rojo analogies; locally Sleeper, Florida Canyon, Hycroft, Rosebud are of similar mineralization style and in the same geological environment.
- Grab samples of float and bedrock shear zone mineralization averages 0.5 to 0.7 gpt Au and 52 to 60 gpt Ag (68 samples); Grabs of breccia mineralization average .34 gpt Au and 78 gpt Ag (21 samples).
- Pyrite-gold association, oxidized at surface; planned IP geophysical survey to test for size and continuity at depth.
- Easy access for drilling; roads transect the main showing area.
Gold was first discovered in 1875 and a small amount of production from high grade quartz veins is recorded up to 1926. Little modern exploration has been carried out on the property. Seven shallow RC holes were drilled by a private group in 1981. Results are unknown and only 3 collars have been located.
The current owners have completed rock sampling and mapping programs and have defined a 1,200 m by 600 m zone of alteration and gold enrichment, open to the east, south and west. Outcrop exposure is minimal.
Pacific Ridge optioned the property in August, 2016.
Poker Brown is located about 39 km north of Lovelock, Nevada and 12 km northwest of the Rye Patch Dam. The property sits in a low pass between the Antelope Range, also known as the Majuba Hills, to the north and the Trinity Range to the south.
Access from Interstate 80, 190 km northeast of Reno, is via the Rye Patch Reservoir exit onto Nevada Route 401 and then about 18 km to the centre of the property.
Poker Brown lies within the Basin and Range Province of Western North America. The property lies within the Midas Shear, a long-lived basement structure that juxtaposes Proterozoic basement to the southeast with Paleozoic basement to the northwest. The western edge of the Proterozoic basement is well endowed metallogenically as it hosts numerous precious metal mines and prospects.
The three major lithologies underlying the area of the Poker Brown claim group include the Triassic Auld Lang Syne Group undifferentiated slate, Cretaceous granodiorite to granite batholiths, stocks and dikes and Miocene subaerial bimodal volcanics.
The oldest rock in western Pershing County is the undifferentiated slate member of the Triassic Auld Lang Syne Group. It is generally a dark gray to tan slate with a moderate slaty cleavage. Interbeds of quartzose sandstone are common but not abundant. At the Poker Brown property, the cleavage has a northeast strike with moderate to steep northwest dip. During the Jurassic-early Cretaceous Nevadan Orogeny, the Auld Lang Syne Group was folded with regional west-verging thrust faults and associated low-grade metamorphism.
Cretaceous granodiorite to granite intrudes the Auld Lang slate. There are numerous intrusives in Pershing County that range in size from batholith scale to small stocks less than a kilometer in diameter. Proximal to Poker Brown, the stocks are less than 4km in diameter. Most ages fall into the 85-95 Ma range.
The Tertiary volcanic assemblage is widespread in northwest Nevada. It covers an extensive area directly west of Poker Brown, although there are no Tertiary volcanics on the Poker Brown prospect. The volcanics erupted onto an erosional surface and rest on both the Triassic slate and Cretaceous intrusives. Their composition is bimodal, as mafic flows and tuffs and felsic ash flow tuff with lesser flows, domes, and associated high-level felsic stocks and dikes. Eruption of these volcanics started about 16 Ma with the onset of continental extension that resulted in the basin and range structure that typifies Nevada's physiography. Many of the epithermal gold-silver systems in northern Nevada are hosted in the upper rhyolite section of the volcanics and are an integral part of the bimodal volcanism.
Nevada experienced a period of moist tropical climate in Miocene time prior to uplift of the Sierra Nevada Range to the west. The heavy rainfall generated an abundance of shallow fresh water lakes in the newly forming intermontane basins. It has been postulated that the wet climate, coinciding with the bimodal volcanism and tectonic extensional structures were important contributing factors to the epithermal metallogenesis by providing abundant fluid, heat sources and plumbing systems for the evolving, precious metal-enriched hydrothermal systems.
There are three styles of Tertiary alteration-mineralization on the Poker Brown Prospect:
Shear and Stockwork: The main exploration target is a 600m wide band of weak to advanced hydrothermally altered slate with an auriferous quartz-limonite veinlet stockwork. It is exposed for 1,200m along strike and is covered to the west by post-mineral volcaniclastics and by Recent alluvium to the east. Exposure is poor on the prospect, most rock exposures are limited to prospect pits and trenches. Alteration-mineralization consists of variably bleached and iron-stained clay-sericite-quartz-limonite alteration with a wide-spaced stockwork of vuggy comb quartz-limonite veinlets up to 10 cm thick. The interbedded quartz sandstone displays more intense alteration than the surrounding slate and assays up to 5 g/t gold.
There are four known shear zones that cut the altered slate with up to 10% sheeted quartz-limonite and gossan veins that strike northeast with steep northwest dips. Alteration tends to be bleached to acid-leached sericite-clay-quartz-limonite, with a few percent fine disseminated limonite and limonite paint on fractures. The width of veining varies from a few meters up about 50m. Fifty-six grab samples from the four east-northeast striking shears average 0.68 g/t Au and 60 g/t Ag with the 10 high-grade assays cut to 2.0 g/t Au and 200 g/t Ag. Twelve grab samples taken from the two north-northwest striking shears average 0.50 g/t Au and 52.5 g/t Ag. The gold-silver mineralization associates with anomalous arsenic-antimony and low mercury-selenium.
Breccia: A 200 m by 400 m sericite-clay-calcite altered hydrothermal breccia occurs at the west end of the prospect. Twenty-one breccia samples from pit dumps and float and average 0.34 g/t Au and 78 g/t Ag. Mineralization consists of hair-line to 0.5cm limonite-quartz veinlets and minor to 5% disseminated limonite grains in the matrix. There are also clasts of quartz-limonite veinlets. In addition, there are scattered clay-altered pebble breccia and silicified breccia dikes with minor fine-grained quartz porphyry and felsite clasts. A grab sample assayed 0.62 g/t gold.
Quartz Veins: The oldest style of mineralization found on the prospect consists of granodiorite-hosted quartz vein stockwork with disseminated galena-sulfosalts. The vein quartz is glassy and massive with poorly formed cleavage fractures perpendicular to the vein margins. Dark green tourmaline is a common accessory as coarse clusters, most often found along the vein margin. The average width is between 10-30cm and occasionally the veins swell up to 0.5m. Sulfides (galena and minor sulphosalts) are limited to less than 2% of the vein material. Most of the historic workings at Poker Brown were developed to exploit these veins.
Pacific Ridge has an option to earn a 100% interest in the Poker Brown property by making staged payments totaling US$1 million and making advanced royalty payments of US$940,000 to the underlying property owner over 8 years. No payments are due in year one. In addition, two bonus cash payments of US$500,000 are payable on cumulative exploration expenditures of US$5 million and US$8 million. Underlying royalties include a 2.5% NSR that can be bought down to 2% for US$500,000 and a 0.5% NSR capped at US$500,000.