|Name:||Gold Springs project|
|Ownership:||100% Gold Springs Resource Corp.|
|Location:||Straddles eastern Lincoln County, Nevada, and western Iron County, Utah. (the Great Basin of western USA)|
|Status:||Advanced exploration stage gold project - Completed PEA.|
|Targets:||Multiple targets with four resource zones open for expansion|
|Potential Development:||Shallow open pit, low sulphidation, heap leach potential|
|Outlook:||District-scale property with medium-term potential with drilling for resource upgrade and expansion at the Jumbo Trend and for identification of high-grade mineralization at the new Homestake Target.|
2015 Preliminary Economic Assessment for the Gold Springs Project.
The PEA base-case scenario uses a US$ 1,300 gold price per ounce and US$ 21 silver price per ounce and demonstrates the potential of the Gold Springs project to be a robust gold mine with compelling project economics.
Robust economics: After-tax NPV5% of US$ 92.1M and an IRR of 35.8% at a $1,300 per ounce gold price.
Signficant Leverage to gold price: US$ 162M NPV5% at recent gold price of US$ 1,600 per ounce.
Technically-simple project: shallow open-pits, heap-leach with a Merrill-Crowe process.
15,000 tpd operation, with a 9-year Life-of-Mine (“LOM”), and a low strip ratio of 2:1.
Pre-production capital cost of US$ 55M and sustaining CapEx of US$ 24.8M once in production.
Cash cost per gold ounce of US$ 669 and AISC per gold oz of US$ 863;
A payback period of 3.1 years.
LOM payable production of 428K gold ounces and 4.9M silver ounces;
US$ 133M of cumulative after-tax free cashflow;
PEA Sensitivity Analysis to Gold Price (In US$)
|Gold Price per ounce||$1,400||$1,600||$1,800|
All data is from the technical report “Amended Technical Report and 2017 Mineral Resource, Gold Springs Project,” dated July 27, 2017 and with an effective date of March 29, 2017, authored by Global Resource Engineering Ltd (GRE) and Kurt Katsura and prepared in accordance with NI 43-101 Standards. Cash Operating cost per gold ounce is net of silver credit and includes mining, processing, G&A, and operating cost contingency; AISC (Fully-loaded cost per gold ounce) includes Cash Operating Costs plus sustaining capital, federal, state and local taxes and excludes initial capital. The portion of the project subject to the Preliminary Economic Assessment (“PEA”) does not have royalties. The PEA is preliminary in nature, it includes inferred mineral resources that are considered too speculative geologically to have the economic considerations applied to them that would enable them to be categorized as mineral reserves, and there is no certainty that the PEA will be realized
The Gold Springs Project covers approximately 7,847 hectares, comprised of federal lode claims, Utah State leases, and patented mining claims held through leases and purchases
The district-scale property is a target-rich environment with four resource zones defined thus far – North Jumbo, South Jumbo, Grey Eagle and Thor. While all are open to expansion, the priority targets are to extend the North Jumbo and South Jumbo in their own surronding areas and towards each other along a 5.5-kilometer Jumbo Trend.
The Company has identified 26 drill-targets based on +1 g/t gold (Au) outcropping samples, geologic and structural modeling, and geophysical results. Gold Springs is somewhat unique in that all of the known resources and targets are exposed on surface. With further exploration work, it is expected that additional targets will be developed under post-mineral cover.
The project encompasses several historical mining districts including the Deer Lodge, Fay, and the Eagle Valley districts, all within Nevada, and the Gold Springs District in Utah. The project area contains hundreds of historical workings, which began around 1897 with several mines that produced gold intermittently until the early 1940s. The Company has been involved with the Gold Springs Project since 2010. Summaries of past exploration, drilling and resource estimates are detailed in the 2017 NI 43-101 report and previous reports filed on SEDAR.
Since 2010, the Company has completed +300 drill holes at Gold Springs for a total of 44,600 meters.
The Company has completed resource estimates in accordance with NI 43-101, based on the the assay results from drill holes completed through 2016, for the Jumbo (now referred to as North Jumbo) and South Jumbo resources located in Utah and the Grey Eagle and Thor resources located in Nevada.
The North Jumbo and South Jumbo are priority targets, located approximately 1.5 km apart at the northern and southern ends of the 5.5-km Jumbo Trend. Grey Eagle is hosted within a collapsed caldera margin while Thor is representative of a deeper exposure of the higher-grade veins typical of epithermal systems. The Company drilled 28 holes in 2017, mostly focused on the South Jumbo resource, which are not included in the most recent resource calculations. These holes were designed to expand the current resource and to better define the high-grade gold distribution within this resource.
In November 2019, the Company drilled 14 holes at the Homestake target, 700 metres east of the Grey Eagle resource, on the Nevada side of the Gold Springs project. The Homestake target includes the historic Homestake mine and mill, which was in operation during the late 1800s and early 1900s. The Homestake target is highlighted by two main parallel 3-4-metre-thick gold-bearing high-grade veins separated by 20-30 metres of brecciated and silicified rocks with intermediate gold grades. The package of veins and breccia is surrounded by a wide low-grade stockwork zone.
Gold mineralization at Gold Springs is characterized by structurally controlled vein and stockwork systems that are laterally extensive, forming wide corridors of mineralization that are traceable over strike lengths of several kilometers. The structural zones are a combination of extensional and lateral faults, as well as ring fracture systems and radial faults associated with caldera margins.
Within these structurally prepared zones, mineralization takes the form of discreet veins, breccias, sheeted vein zones, stockwork veins, and zones of disseminations. The veins exhibit quartz, adularia, and low sulfide contents that are typical of low-sulfidation epithermal deposits. Examples of this deposit type include Round Mountain, Nevada; Midas, Nevada; the Republic District, Washington; and Hishikari, Japan.
These systems have been correlated with fossil hot springs, and the hydrothermal systems that underlie them are commonly found in a caldera setting. Some of the characteristics that help classify the Gold Springs systems as a low-sulfidation epithermal deposit are the observed textures of quartz, adularia, and calcite in the vein deposits. These veins of varying dimensions are typically surrounded by broad areas of stockwork and breccia-hosted mineralization, and/or areas of altered and fractured wallrock where increased permeability hosts disseminated gold mineralization.
In March 2017, Gold Springs Resource Corp. filed the NI 43-101 Technical Report and updated Resource Estimate for Gold Springs on SEDAR.com. Please refer to the Technical Report for important Qualified Person, technical and other disclosures.
The 2017 pit-constrained resource, using a 0.25 g/t gold cutoff, with an effective date of March 29, 2017, consists of:
|Tonnes (000)||g/t||Oz (000)||g/t||Oz (000)|
|Gold Springs Property-Wide Resource – using a 0.25 g/t gold cutoff|
|Jumbo Trend Resource - Jumbo North and Jumbo South|
|Grey Eagle and Thor Resource|
|Tonnes (000)||g/t||Oz (000)||g/t||Oz (000)|
All data is from the NI 43-101 report, “Amended Technical Report and 2017 Mineral Resource, Gold Springs Project,” dated July 27, 2017 and with an effective date of March 29, 2017. Mineral resources that are not mineral reserves, do not have demonstrated economic viability. In addition, ‘inferred resources’ have a great amount of uncertainty as to their existence, and economic and legal feasibility. It cannot be assumed that an inferred resource will be upgraded to a higher category. Ounces are gross, as they have not been adjusted for metallurgical recoveries. Numbers have been rounded, which may lead to some numbers not totaling exactly.
Metallurgical test work, involving bottle roll tests at various size fractions and column tests, produced positive results indicating that the material from the North Jumbo and Grey Eagle resources is amenable to heap leaching with positive recoveries for gold.
During 2015, Kappes Cassiday Associates (KCA), Reno, Nevada, completed a set of column leach tests on three samples each from the North Jumbo and Grey Eagle. The material was crushed to 100% passing 9.5 millimeters and was leached in columns 75 millimeters in diameter and 0.6 meters in height. The material leached quickly, and the majority of the gold leaching occurred within the first 20 days (84% to 97% of total leached) and was substantially completed in 60 days.
Silver leaching was typically much slower. The cyanide concentration was increased at approximately day 85, which did result in an increase in silver recovery, from little change to a 10% increase. This change in reagent concentration significantly increased the cyanide consumption.
Using a simple average, gold recovery for the Grey Eagle and North Jumbo area were 77% and 68%, respectively. This does not take into account weighting of the recovery by proportion of ore type as unique ore types were not separately weighed prior to combining for testing. Globally between the two resource areas, the recovery averaged 73% for gold. Silver recovery averaged 16% and 47% for Grey Eagle and Jumbo, respectively. The cause for the lower silver recovery experienced for Grey Eagle is unknown at this time.
2015 KCA Column Tests for Grey Eagle and North Jumbo
|Sample Description||Crush Size (mm)||Days of Leach||Calculated Head (Gold g/t)||Calculated Head (Silver g/t)||Extracted Gold||Extracted Silver||Consumption NaCN (Kg/t)||Cement Addition (Kg/t)|
|GE Trench 1||9.5||141||2.548||12.01||82%||23%||14.31||2.01|
|GE Trench 2||9.5||141||2.446||12.00||87%||15%||13.60||2.05|
|GE Trench 3||9.5||141||0.899||11.01||63%||9%||11.61||1.95|
|Jumbo Met Samples 1-4||9.5||141||0.679||12.52||92%||37%||14.61||2.02|
|Jumbo Met Samples 5-7||9.5||141||0.843||17.28||56%||45%||12.04||2.03|
|Jumbo Met Samples 8-11||9.5||141||0.370||20.33||57%||58%||12.69||2.01|
NaCN - sodium cyanide
Additional column testing was completed on the Jumbo resource material in 2016 using Resource Development Inc. (RDI), Denver, Colorado. The metallurgical tests were conducted over 282 days to look at extraction rates over the short term and long term after a “rest period” in which no additional cyanide solution was applied. The extraction values are shown below.
2016 RDI Column Tests - Estimated Gold Extractions for North Jumbo
|Column||Final Extraction*||Calculated Head Grade|
|Gold (%)||Silver (%)||Gold (g/t)||Silver (g/t)|
* extractions after 157 days of leaching and 125 days of rest
The three columns covered a wide range of grades varying from 1.09 g/t to 0.23 g/t gold, with good recoveries even from the lower grade material. Approximately 22 kg of each type of mineralized material, crushed to a P80 of ¾ inches, were loaded into 4-inch diameter columns approximately 6 feet high. The final extractions over time are shown below.
2016 RDI Column Tests - Large Column Extraction Detail Data with Rest Periods for North Jumbo
|Column||43 day Extraction||84-day Extraction||282-day Extraction after rest period*||Calculated Head Grade|
|Gold %||Silver %||Gold %||Silver %||Gold %||Silver %||Gold g/t||Silver g/t|
*Leach sequence included 84 days of leaching followed by 35-day rest, followed by 44 days of leaching, followed by a second rest period of 90 days, followed by a further 29 days of leaching.
The material was leached and sampled over a long time frame to evaluate how much more gold and silver could be extracted over time and after rest periods during which the cyanide solution is not circulated. As can be seen in the two tables, gold recoveries increased several percent after the rest period, and silver recoveries increased significantly with increases in the double-digit percentages. Approximately 90% of the gold recovery was achieved in the first 12 to 18 days.
There is high potential to expand the current resource base and to identify additional resources at the other targets.
The Company’s goal is to continue drill programs focused on the Jumbo Trend, expanding the resources both north and south. The Jumbo Trend is characterized by extensional and translational structures generally trending north-south. Movement on these structures created favorable zones for gold deposition.
In general, the North Jumbo and South Jumbo resources consist of discreet veins, breccias, sheeted vein zones, stockwork veins, and zones of disseminations over widths of 30-150 meters. The current resources are open along strike and have not been tested at depth. All mineralization starts at surface with the deepest holes reaching a depth of just 200 meters (m) below surface.
In addition to the Jumbo Trend, another high priority target is the newly acquired Homestake claims located in Nevada, 1,000 m east of the Grey Eagle resource. The Homestake mineralization is largely hosted in two stacked, 2-4 m wide, westward dipping, banded quartz veins that are controlled by major north-south structures that run the length of the 1.8-km claims.
The Homestake veins are well exposed for 650 m in historic slot cuts and as outcrops before they are concealed by post mineral cover to the north and south. Host rock to the veins are oxidized andesites that have been hydrothermally brecciated and contain stockwork quartz veining. Together, breccia and stockwork zones extend up to 400 m widths around the vein systems before they are concealed by post mineral cover.
High-grade Au occurs in the quartz veins with strong gold and silver mineralization occurring in the host rock as well. These breccias and stockwork zones extend to the west where they host the Iris vein that roughly parallels the Homestake veins and is easterly dipping. Both the Homestake veins and the Iris vein are known to contain high-grade Au values (up to 15 g/t Au at Homestake and 38 g/t Au at Iris), with parallel trends and opposing dips between the two vein sets that there is high potential for significant gold grades at their intersection. In the north, breccias contain up to 68 g/t Au in outcrop, though typical assay results are 0.29 to 2.4 g/t Au from the breccia and stockwork zones.