The Lawyers Project Is Located In The Prolific ‘Golden Horseshoe’
The Lawyers Property covers 144 km2 of highly prospective rocks in the northeastern region of the prolific metal-endowed Stikine Terrane, British Columbia, Canada. Magmatic events in Stikine during the Late Triassic and Early Jurassic were the driving source for the development of mineralizing porphyry and epithermal systems. On both the east and west sides of the Bowser Basin the same magmatic and mineralizing events are recognized (Logan and Mihalynuk, 2014), forming an arch of gold and polymetallic mineralization; which is depicted herein as the ‘Golden Horseshoe’ which includes the Golden Triangle (Figure 1).
Figure #1 – Map of the Golden Horseshoe
The Lawyers Project straddles an important stratigraphic horizon between rocks of the Upper Triassic Stuhini Group and Lower Jurassic Hazelton Group that define an important geological unconformity with many of the deposits in the Golden Horseshoe concentrated along it. The project is also located in a proven and profitable mining jurisdiction, only 45 km northwest of the Kemess gold-copper mine (Figure 2). The Golden Horseshoe provides a visual context for the mines, discoveries and common geology of the Golden Triangle and Toodoggone regions, which forms a prolific metalliferous arch that includes the Quesnel and Stikine terranes.
Figure #2 – Project map with local infrastructure
1980 vs 2022
At the heart of the Laywers Trend is the structurally controlled Cliff Creek, Dukes Ridge, Phoenix, and AGB zones that are located within a large 5 km by 8 km radiometric anomaly that is coincident with potassic alteration, associated with a low-sulphidation epithermal system (Figure 3). The limited historical underground production at the AGB and Cliff Creek zones targeted the high-grade veins associated with this large epithermal system. However, recently acquired data, geological compilation, and reinterpretation has revealed significant potential to add gold and silver ounces within these zones and across the entire mineralizing system. New drill results are providing previously unrecognized bulk-tonnage, near-surface intercepts that envelope the higher-grade intervals of gold and silver mineralization. These results are from within the footprint of the historically mined areas, but also include significant gold-silver intercepts along strike, and at depth. The surface expression of the mineralization is coincident with pervasive potassic alteration, large gold-in-soil anomalies, and anomalous rock and trench results.
Select high-grade drilling intercepts from the Lawyers Trend include:
- 259.76 g/t Au & 3,320.3 g/t Ag over 3 m*
- 108.36 g/t Au & 911.2 g/t Ag over 7 m*
- 86.06 g/t Au & 583.83 g/t Ag over 7 m*
- 52.02 g/t Au & 846.44 g/t Ag over 3 m*
- 12.67 g/t Au & 143.39 g/t Ag over 28 m*
Select bulk-tonnage drilling intercepts from the Lawyers Trend include:
- 6.96 g/t Au & 254.70 g/t Ag over 57.9 m*
- 5.76 g/t Au & 128.65 g/t Ag over 33.53 m*
- 4.06 g/t Au & 409.06 g/t Ag over 40.9 m*
- 3.78 g/t Au & 82.40 g/t Ag over 35.0 m*
- 2.68 g/t Au & 82.57 g/t Ag over 36.5 m*
*Drill hole length
** Based on limited information from historical mine level plans and ore block models parts of the results above have been mined. However, both high-grade and bulk-tonnage drill intercepts and surface mineralization extend beyond the known workings and the system remains open along strike and at depth.
The Lawyers property is predominantly underlain by a shallow northwest-dipping sequence of volcanic and sedimentary rocks of the Lower Jurassic Toodoggone Formation (Figure 3), part of the Hazelton Group that is exposed throughout the prolific metal-endowed Stikine Terrane. The Toodoggone Formation can be divided into upper and lower volcanic cycles as illustrated on the simplified stratigraphic column in Figure 4. The Lawyers property is predominantly underlain by lower cycle rocks comprised of thick sequences (>300 m) of dacitic and andesitic tuffs and flows. These volcanic strata erupted concurrently with the development of deeply rooted faults that focused both magmatism and mineralization (Figure 3). Magmatism is expressed as the Black Lake intrusive suite that outcrops in the southern region of the property (Diakow et al., 1993). Locally Asitka and Takla Group rocks are exposed along the margins of the Black Lake intrusive and are in part fault bounded. Similar relationships are often observed in the southern Toodoggone and spatially associated with porphyry style mineralization, including at Kemess.
Localized conglomerates and volcaniclastics within the lower cycle are confined within blocks dropped by steeply dipping syn-volcanic faults and can potentially be used as a vector towards epithermal mineralization. The entire Toodoggone Volcanic sequence is unconformably overlain by the younger Sustut sediments.
Figure #3 – Geological map of the Lawyers property and accompanying cross sections showing the relationship between structure, stratigraphy and epithermal mineralization across part of the central Lawyers Trend.
Figure #4 – Simplified stratigraphic section for the Lawyers project and the broader Toodoggone region. The different types of intrusive rocks, mineralization, and the time period for which they span is illustrated on the right side of the diagram.
The lawyer’s property has undergone a relatively simple brittle deformation history of syn-volcanic graben development and subsequent strike-slip deformation. The most dominant structural features on the property are a series of well-developed NW-NNW (310-340°) striking faults that are subvertical to steeply SW or NE dipping. They typically show evidence of normal displacement with localized, late, strike-slip reactivation. These are the oldest structures on the property and represent syn-volcanic growth faults that formed during Lower Jurassic extension and block faulting.
The orientation and characteristics of the mineralized zones within the Lawyers Trend are consistent with the development of robust hydrothermal systems within a pre-existing NW-NNW trending fault and fracture system. This system is likely reflecting the original volcanic basin geometry, and these structures acted as a conduit for fluids to migrate and precipitate metals. The NW structures and associated mineralization are locally offset by E-W and SW-NE trending strike-slip faults, typically with less than 10 metres of displacement. The structural relationships observed in outcrop and drill core are also observed in the magnetic data, providing numerous new exploration targets.
Volcanic strata on the property are only very weakly altered and original textures are generally well preserved. Narrow localized zones associated with mineralization in the main zones do show intense silicification and potassic alteration. While a variety of alteration is observed across the property, ranging from a massive advanced argillic zone north-west of Cliff Creek to the strong quartz-sericite-pyrite alteration concentrated along structures in the Marmot area. The alteration, variation and zonation suggest that the epithermal mineralization on the Lawyers property was part of a large-scale hydrothermal system.
2022 Preliminary Economic Assessment
On September 29, 2022, Benchmark Metals Inc. filed its Preliminary Economic Assessment (“PEA”) to SEDAR on the Lawyers gold-silver project. The final NI 43-101 Technical Report has provided some enhanced metrics over the initial results published on August 16, 2022. The Project has strong infrastructure in place or nearby and is within a first-class mining jurisdiction. The PEA presents a significant open pit mining operation with base case, attractive economics that has potential for additional gold-silver ounces and optimized results through facility design adjustments in future advanced engineering studies.
The potential for additional higher-grade mineralization below and adjacent to the various pits accessed through underground mining will be reviewed. Trade-off studies and more advanced engineering has the potential to add more ounces and improve results.
- Pre-tax NPV5% of C$939M, with an IRR 31.4%, and 2-year payback
- Pre-tax Net Operating Income of C$2,157M
- Base case metal price parameters of US$1,735 per ounce of gold and US$21.75 per ounce of silver
- After-tax NPV5% of C$589M, IRR 24.1%, and 2.8-year payback
Capital light development
- Initial capital of C$484M (including C$72.8M in contingency)
- Life of Mine capital of C$632M
- Strong 1.9:1 Pre-tax NPV5% to Initial Capex ratio
- Minimal pre-strip limited to TSF starter dam construction
Low All-In Sustaining Costs (AISC)
- US$ 786/Au oz (net of by-products)*
Long Mine Life with Expansion Opportunity
- Total resource production of 46.7 M tonnes over 12-year mine life
- Average annual production of 163k AuEq ounces
- LOM production 1.95M payable AuEq ounces
- Average AuEq Head Grade of 1.41 g/t
- Average gold recovery of 92.4%
*All-In Sustaining Costs (Net of By-Products) are calculated for the purpose of the Study as the sum of all operating costs (mining, processing, site administration and refining), reclamation and sustaining capital, minus the revenue from Ag, all divided by the gold ounces sold to arrive at the per ounce Au figure.
2022 Identification of Exploration Drill Targets
In July 2022 Benchmark announced the identification of new exploration drill targets. There are three major targets at AGB, and at Kodah and Round Mountain, which are north of AGB.
A large resistive body adjacent to AGB as defined by 2D Lines. This is posited to represent a large steeply dipping silicified body associated with a fault system. This is the same signature seen elsewhere at the Lawyers project.
Two soil anomalies 3 km north of AGB coincident with VLF geophysical anomalies. These are targets that have not seen historical or contemporary drilling.
Kodah and Round Mountain prospects have robust soil anomalies in gold, silver, and elements associated with epithermal style mineralization. Historic rock grabs have included 29.14 g/t Au and 2125.7 g/t Ag, 26.06 g/t Au and 2142.9 g/t Ag , and 18.86 g/t Au and 1508.5 g/t Ag. Ground geophysics, prospecting, mapping, and infill soils are ongoing at these prospects.
2022 Mineral Resource Estimation
In June 2022 Benchmark released its expanded bulk-tonnage Mineral Resource Estimate (MRE) for its Lawyers Gold-Silver Project. The 2021 and winter 2022 drill program significantly de-risked the project with approximately 95% of the open pit mineral resource within the Measured & Indicated classification.
- Indicated Mineral Resource of 3.14 million ounces grading 1.45 grams per tonne (g/t) gold equivalent (AuEq), as per Table 1;
- Inferred Mineral Resource of 415,000 ounces grading 2.63 g/t AuEq;
- The Mineral Resource is amenable to both open pit and underground mining methods;
- Pit constrained (open pit)
- Measured & Indicated –2.964 M oz AuEq
- Inferred – 78 k oz AuEq
- Out of Pit (potential underground below or adjacent to the pits at Cliff Creek and AGB)
- Measured & Indicated – 177 k oz AuEq
- Inferred – 337 k oz AuEq
- Pit constrained (open pit)
- The Mineral Resource shows excellent continuity and consistency, demonstrated by increasing AuEq cut-off grades having marginal impact on the pit constrained AuEq ounces;
- The MRE formed the basis for the Preliminary Economic Assessment (PEA) that was filed on September 29, 2022, and;
- All of the zones remain open for further expansion and Benchmark is fully funded for additional drilling, engineering and environmental programs into 2023.
Table 1. Lawyers Expanded Mineral Resource Estimate (1-9)
|Mineral Resource Area||Classification||Tonnes
|Pit-Constrained Mineral Resource Estimate @ 0.4 g/t AuEq* Cut-off|
|Out-of-Pit Mineral Resource Estimate @ 1.5 g/t AuEq* Cut-off|
|Total Mineral Resource Estimate @ 0.4 g/t Au-Eq* Cut-off Pit-Constrained & 1.5 g/t AuEq* Cut-off Out-of-Pit|
|M & I||67,376||1.16||22.9||1.45||2,521||49.6||3,141|
- Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability.
- The estimate of Mineral Resources may be materially affected by environmental, permitting, legal, title, taxation, socio-political, marketing, or other relevant issues.
- The Inferred Mineral Resource in this estimate has a lower level of confidence than that applied to an Indicated Mineral Resource and must not be converted to a Mineral Reserve. It is reasonably expected that the majority of the Inferred Mineral Resource could potentially be upgraded to an Indicated Mineral Resource with continued exploration.
- The Mineral Resources were estimated in accordance with the Canadian Institute of Mining, Metallurgy and Petroleum (CIM), CIM Standards on Mineral Resources and Reserves, Definitions (2014) and Best Practices Guidelines (2019) prepared by the CIM Standing Committee on Reserve Definitions and adopted by the CIM Council.
- Historical mined areas were removed from the block modelled resources.
- Metal prices used were US$1,750/oz Au and US$20/oz Ag and 0.78 US$ CDN$ FX with process recoveries of 90% Au and 83% Ag. A C$14.50/t process cost and C$5/t G&A cost were used. The Au:Ag ratio was 80:1 for the purposes of calculating AuEq.
- The constraining pit optimization parameters were C$3.15/t mineralized and waste material mining cost and 50° overall pit slopes with a 0.40 g/t AuEq cut-off.
- The Out-of-Pit Mineral Resource grade blocks were quantified above the 1.5 g/t AuEq cut-off, below the constraining pit shell and within the constraining mineralized wireframes. Out-of-Pit Mineral Resources selected exhibited continuity and reasonable potential for extraction by the long hole underground mining method. Differences may occur in totals dues to rounding.
- Source: APEX (2022)
Quality Assurance and Control
Results from samples were analyzed at ALS Global Laboratories (Geochemistry Division) in Vancouver, Canada (an ISO/IEC 17025:2017 accredited facility). The sampling program was undertaken by Company personnel under the direction of Rob L’Heureux, P.Geol. A secure chain of custody is maintained in transporting and storing of all samples. Gold was assayed using a fire assay with atomic emission spectrometry and gravimetric finish when required (+10 g/t Au). Analysis by four acid digestion with 48 element ICP-MS analysis was conducted on all samples with silver and base metal over- limits being re-analyzed by atomic absorption or emission spectrometry. Rock chip samples from outcrop/bedrock are selective by nature and may not be representative of the mineralization hosted on the project.
Michael Dufresne, M.Sc., P.Geol., P.Geo., an independent director of the Company, also serves as a Technical Advisor and is the Qualified Person, as defined by National Instrument 43-101, responsible for reviewing and approving the technical content of all materials publicly disclosed by Benchmark, including the contents of this website.