Benchmark Metals Inc. is pleased to report evidence for multiple stages of precious metal mineralization at the Lawyers Gold & Silver Project, located in the Golden Triangle region of British Columbia, Canada.
CEO John Williamson commented, “The Lawyers Project presents a tremendous opportunity for the development of near-surface or buried bulk tonnage deposit. After a comprehensive exploration program, we are excited to have discovered evidence suggesting the occurrence of multistage events of precious metal mineralization that may explain the high-grade results from recent rock grab samples. The geological team is seeing mineralization that resembles a porphyry system.”.
Lawyers Geological Potential
The porphyritic andesite with potassic (k-feldespar + shreddy biotite) overprinted by phyllic alteration (quartz + sericite + pyrite) resembles porphyry-type disseminated bulk tonnage mineralization. This type of mineralization typically yields lower gold-silver grades (e.g. 0.525 grams per tonne Au, 15.4 g/t Ag over 2m; Figure 1.a) and is widely spread within the property.
The alteration mineral association of alunite and dickite observed over 0.5km to 2km trends to the west of the main mineral deposits (AGB, Cliff Creek, and Dukes Ridge), indicating high sulfur fugacity characteristic of high-sulfidation precious metal deposits, although no lithocaps, vuggy silica, or high-sulfidation-state hypogenic sulfides such as covellite, digenite, or enargite have been identified. This may suggest the presence of a magmatic-hydrothermal system that includes high-sulfidation precious-base metal deposits possibly linked to deeper porphyry-type mineralization that may have been eroded and structurally dislocated.
Furthermore, high Au-Ag grades (220g/t Au, >10,000g/t Ag) have been observed related to electrum and silver sulphosalts associated with calcite, adularia, and quartz with crustiform and cockade textures. This mineral association and textures are more characteristic of epithermal low-sulfidation precious metal deposits and has been observed overprinting the formerly described “porphyry-type” mineralization in the Phoenix area, see Figure #1 below.
A photo accompanying this announcement is available at http://www.globenewswire.com/NewsRoom/AttachmentNg/f2bade22-d9da-4ab3-88c4-ba2b5a0825d5
This evidence increases substantially the economic potential of the Toodoggone district.
Benchmark has commenced academic studies, including XRD analyses to verify alteration minerals identified in the field with TerraSpec analyzers, ore petrography supported with microprobe analyses to properly characterize the mineral paragenesis, fluid inclusion microthermometry to identify temperature and salinities of ore-forming fluids, as well as geochemistry and geochronology of both alteration minerals and associated magmatic rocks.
The overall objective of these academic studies is to gain a better understanding of the ore-forming processes at both district and regional scales that would enable us to conduct exploration more efficiently.
The Lawyers Project sits within the Toodoggone district, which also contains the Shasta, Baker, Bonanza, and the world-class Kemess and Kemess North copper gold deposits, and numerous other gold-silver-copper prospects are in various stages of exploration and development. Clark and Williams (1990) described a range of deposits from gold-rich porphyry-style deposits, to deep-seated precious and base metal bearing stockworks and veins, to near-surface replacement-type gold mineralization. The most economically significant deposits exhibit characteristics typical of epithermal alteration and mineralization of both adularia-sericite and acid sulphate affinities (Clark and Williams, 1990).
Age dating of the adularia-sericite alteration around the mineralisation at the Lawyers (AGB and Cliff Creek) and Shasta deposits suggest that they formed between 187-190 Ma (Clark and Williams-Jones, 1990). The timing of mineralisation, as well as rocks which host the Lawyers mineralisation (Toodoggone Volcanics), overlaps with the age and emplacement of several well known porphyry and epithermal deposits in northwest British Columbia (including Kerr-Sulphurets-Mitchell, Snowfield, and Brucejack (Febbo, 2016; Tombe et al. 2018)). This timing marks a shift in the volcanic arc-development resulting in a metallogenic epoch hosting many significant deposits in the Stikinia Terrane.
The work to be conducted by Benchmark will help to elucidate the relationship between such a range of mineralization styles within the district.
2018 Exploration Program
During the current field season, Benchmark collected 1,041 soils samples covering 29 line kilometers and over 7.2 km2. Several areas of anomalous gold have been identified on the soil grids, as well as localized geochemical anomalies in As, K and Zn. Mapping and prospecting was conducted and a total of 312 rock samples were collected across the property. An airborne geophysical survey was also conducted over the property at 100 meter line spacing. Benchmark completed a total of 4,116 meters of drilling, including 1,493 meters of diamond core drilling and 2,623 meters of reverse circulation drilling at the Dukes Ridge, Cliff Creek and Phoenix Zones. Several intersections of veining, brecciation and fine-grained sulfosalts were observed in the drilling, occurring in areas with little existing drill hole data.
Lawyers Gold and Silver Project
The Lawyers Property and formerly producing Cheni Gold and Silver Mine is located 45 km northwest of the Kemess Gold and Copper Mine. The Property contains an existing Mineral Resource hosts a minimum of 16 existing gold and silver occurrences that were never fully mined, developed or explored. Work during the 2018 exploration program has focused on mineralized zones with exposure at surface. Each zone remains open at strike, width and depth, extending across hundreds of meters. The 99km2 prospective land package presents a unique opportunity for Benchmark to carry out exploration on a ‘camp’ scale. There remains excellent potential for the discovery of additional low and high-sulphidation epithermal precious metal deposits like those that have been discovered and explored to date in the Golden Triangle region. In addition, there exists the possibility for the discovery of near-surface or buried ‘bulk tonnage’ deposits which may offer the advantage of economies of scale should future mine development occur.
Quality Assurance and Control
Results from samples were analyzed at ALS Global Laboratories (Geochemistry Division) in Vancouver, Canada (an ISO 9001:2008 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 (+10g/t Au). Analysis by four acid digestion with 48 element ICP-MS analysis was conducted on all samples, with silver and base metal overlimits 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.
The technical content of this news release has been reviewed and approved by Michael Dufresne, M.S.c, P.Geol., P.Geo., a qualified person as defined by National Instrument 43-101.