GR Silver Mining Ltd. has provided wide and high-grade drill results from the company’s underground core drilling program in the Plomosas mine area, as well as validation sampling results from historic drilling, at its 100-per-cent-owned Plomosas silver project in Sinaloa, Mexico.
The underground drilling program is targeting bulk tonnage-style mineralization in the Plomosas Mine Area (following the Company’s recent discovery at level 775, approximately 250 m below surface) aiming to delineate high margin precious and base metals mineralization with potential for large tonnage and scalability.
The successful underground exploration drilling program at the Plomosas Mine Area has discovered extensions to the wide mineralization previously sampled at level 775, both below, and laterally to, previously mined areas. The mineralization is represented by thick intercepts of Au-Ag-Pb-Zn-Cu mineralization hosted in a series of hydrothermal breccias.
Drill intercept highlights from recently completed hole PLI20-042 include (see also Table 1):
83.0 m @ 420 g/t AgEq (2.52 g/t Au, 33 g/t Ag, 0.9 % Pb, 2.9 % Zn and 0.3 % Cu, from 98.0 to 181.0 m), including:
4.0 m @ 1,319 g/t AgEq (9.35 g/t Au, 38 g/t Ag, 0.4 % Pb, 10.5 % Zn and 0.3 % Cu); and
11.0 m @ 1,596 g/t AgEq (9.41 g/t Au, 135 g/t Ag, 5.7 % Pb, 9.8 % Zn and 0.5 % Cu)
1AgEq is based on long term gold, silver, zinc, lead and copper prices of US$1600 per ounce gold, US$16.50 per ounce silver, US$0.85 per pound zinc, US$0.95 per pound lead and US$3.00 per pound copper. The metallurgical recoveries are assumed as 90% Ag, 95% Au, 78% Pb, 70% Zn and 70% Cu.
2As final interpretation of the 3D orientation of mineralization is incomplete, true widths are unknown at this time and are reported as drilled widths.
Two oriented underground core drill holes (PLI20-03, PLI20-04), drilled by GR Silver Mining, have provided important geological, structural and mineralization data, thus aiding the interpretation of these wide, high-grade zones. This data is assisting in the investigation of additional broad zones of sulphide-rich (sphalerite, galena and chalcopyrite) mineralization hosted in structurally controlled hydrothermal breccias in the Plomosas Mine Area (link to core photos).
Four historic underground drill holes (PLI17-05, PLI17-08, PLI17-15 and PLI17-16), located nearby, were also validated with new sampling by GR Silver Mining. All data and additional new sample results are being incorporated into a 3D geological model (Figure 1).
GR Silver Mining President and CEO, Marcio Fonseca, commented, “These are extraordinary drilling results from the Plomosas Mine Area, indicating potential for size and scalability in the geological model to host attractive precious and base metals mineralization in areas close to existing underground development. We will continue with underground drilling in the vicinity of this polymetallic mineralization in 2021 and will also apply the technical knowledge to look for similar mineralization in other targets in the Plomosas Silver Project.”
The drill hole PLI20-04 represents a 25 m step-out from the previously released high grade discovery at the deepest level (775m RL) of the Plomosas Mine Area (see News Release dated 28 September, 2020 ). The step-out area displays an intersection of two fault systems: the low angle N-S trending Plomosas Fault and high angle NE oriented faults (see cross section 2551950N).
The wide mineralized zone is mainly comprised of high-grade Au-Ag-Pb-Zn hydrothermal breccia, with late disseminated chalcopyrite (Cu) – pyrite rich veins/veinlets. A pervasive chalcopyrite-pyrite quartz stockwork system is common not only on the footwall, but also on the hanging wall of the mineralized hydrothermal breccia. This system is apparently hosted by the two fault systems and also by specific geological units, oxidized andesites and andesitic tuffs, defining a prospective corridor along strike. A similar style of mineralization was recently mapped in the upper levels of the Plomosas Mine Area and is currently the subject of detailed exploration. Based on the recent underground drilling results, GR Silver Mining is continuing the investigation of all historical underground sampling in order to delineate new zones for drilling, aiming to incorporate all new areas in the upcoming NI 43-101 resource estimation.
Table 1 and 2 summarize the most significant assay results for the underground drill holes reported in this News Release.
Table 1: Underground Drill Hole Results – News Release January 05, 2021 (Plomosas Mine Area)
Hole No.TypeFrom (m)To (m)Drilled width (m)Ag g/tAu g/tPb %Zn %Cu %AgEq g/t
PLI20-03UG No significant assays
PLI20-04UG 98.0 181.0 83.0 33 2.52 0.9 2.9 0.3 420
includes 99.0 103.0 4.0 38 9.35 0.4 10.50.3 1,319
139.0 150.0 11.0 135 9.41 5.7 9.8 0.5 1,596
Table 2: Historic Underground Drill Hole Results – News Release January 5, 2021 (Plomosas Mine Area)
Hole No.TypeFrom (m)To (m)Drilled width (m)Ag g/tAu g/tPb %Zn %Cu % AgEq g/t
PLI17-05UG 120.0 125.0 5.0 58 na na na na
PLI17-08UG 80.0 98.7 18.7 31 0.21 1.5 1.6 na 152
includes 91.0 95.6 4.6 88 0.73 5.8 5.3 0.1 512
PLI17-15UG 0.0 41.1 41.1 14 0.35 1.5 2.8 na 180
PLI17-16UG 0.0 32.1 32.1 6 0.39 1.9 1.9 na
As final interpretation of the 3D orientation of mineralization is incomplete, true widths are unknown at this time and are reported as drilled widths. AgEq is based on long term gold, silver, zinc and lead prices of US$1600 per ounce gold, US$16.50 per ounce silver, US$0.85 per pound zinc, US$0.95 per pound lead and US$2.00 per pound copper. The metallurgical recoveries are assumed as 90% Ag, 95% Au, 78% Pb, 70% Zn.and 70% Cu. “na” = no relevant assays. All numbers are rounded. Results are uncut and undiluted. UG: Underground Drill Hole, SURF: Surface Drill Hole
GR Silver Mining believes that the Plomosas Mine Area is part of a much larger low sulphidation epithermal system as indicated by field evidence along one kilometre of strike length, where only 400 m of that strike had previously been drilled. The 2020 underground and surface exploration program defined multiple styles of mineralization, creating an opportunity for the Company to continue discovering new mineralized zones close to the surface.
The scientific and technical data contained in this News Release related to the Plomosas Project was reviewed and/or prepared under the supervision of Marcio Fonseca, P.Geo. He has approved the disclosure herein.
Quality Assurance Program and Quality Control Procedures (“QA/QC”)
The Company has implemented QA/QC procedures which include insertion of blank and standard samples in all sample lots sent to SGS de Mexico, S.A. de C.V laboratory facilities in Durango, Mexico, for sample preparation and assaying. For every sample with results above Ag >100 ppm (over limits), these samples are submitted directly by SGS de Mexico to SGS Canada Inc at Burnaby, BC. The analytical methods are 4-acid Digest and Inductively Coupled Plasma Optical Emission Spectrometry with Lead Fusion Fire Assay with gravimetric finish for silver above over limits. For gold assays the analytical methods are Lead Fusion and Atomic Absorption Spectrometry Lead Fusion Fire Assay and gravimetric finish for gold above over limits.
The recent drill holes, completed by First Majestic from 2016 to 2018, followed QA/QC protocols reviewed and validated by GR Silver Mining, including insertion of blank and standard samples in all sample lots sent to First Majestic’s Laboratorio Central facilities in La Parilla, Durango, for sample preparation and assaying. Additional validation and check assays were performed by an independent laboratory at SGS de Mexico, S.A. de C.V. facilities in Durango, Mexico. The analytical methods applied for these recent holes for Ag and Au assays comprised of Fire Assay with Atomic Absorption finish for samples above Au >10ppm and Ag >300ppm and Gravimetric Finish. Pb and Zn were analyzed using Inductively Coupled Plasma Optical Emission Spectrometry. GR Silver Mining has not received information related to the Grupo Mexico QA/QC and assay protocols and at this stage is considering the information historic for news release purposes.
About GR Silver Mining Ltd.
GR Silver Mining Ltd. is a Mexico-focused company engaged in cost-effective silver-gold resource expansion on its key assets which lie on the eastern edge of the Rosario Mining District, Sinaloa, Mexico.
PLOMOSAS SILVER PROJECT
GR Silver Mining owns 100% of the Plomosas Silver Project located near the historic mining village of La Rastra, within the Rosario Mining District. The Project is a past-producing asset where only one mine, the Plomosas silver-gold-lead-zinc underground mine, operated a 600 tpd crush milling flotation circuit from 1986 to 2001, producing approximately 8 million ounces of silver, 73 million pounds of lead and 28 million pounds of zinc.
The Project has an 8,515-hectare property position and is strategically located within 5 km of the Company’s San Marcial Silver Project in the southeast of Sinaloa State, Mexico.
The March 2020 acquisition of the Plomosas Silver Project included 563 historical and recent drill holes from both surface and underground locations. These drill holes represent an extensive database allowing the Company to advance towards resource estimation and potential project development in the near future.
The Company has commenced an 11,900 m drilling program with surface holes focused on expanding known mineralization along strike in two initial areas, the Plomosas Mine Area and the San Juan Area. Underground drilling included in the program will target the extension of recent polymetallic discoveries at the lowest level (775 m RL, or ~250 m below surface) of the Plomosas Mine Area and six low sulphidation epithermal veins at San Juan Area. Both areas will be the subject of NI 43-101 resource estimations following completion of this drill program.
The 100%-owned assets include all facilities and infrastructure including: access roads, surface rights agreement, water use permit, 8,000 m of underground workings, water access, 60 km – 33 KV power line, offices, shops, 120-person camp, infirmary, warehouses and assay lab representing approximately US$30 million of previous capital investments. The previous owners invested approximately US$18 million in exploration, including extensive geophysics and geochemistry programs.
The silver and gold mineralization on this Project display the alteration, textures, mineralogy and deposit geometry characteristics of a low sulphidation epithermal silver-gold-base metal vein/breccia mineralized system. Previous exploration was focused on Pb-Zn-Ag-Au polymetallic shallow mineralization, hosted in NW-SE structures in the vicinity of the Plomosas mine. The E-W portion of the mineralization and extensions for the main N-S Plomosas fault remain under-explored.
In addition to the resource potential at Plomosas, a review of the existing drill hole database, geophysical surveys and geochemical data covering most of the concession, has defined 16 new exploration targets from which 11 have high priority for future exploration programs.
SAN MARCIAL PROJECT
San Marcial is a near-surface, high-grade silver-lead-zinc open pit-amenable project, which contains a 36 Moz AgEq (Indicated) and 11 Moz AgEq (Inferred) NI 43-101 resource estimate. The company recently completed over 320 m of underground development in the San Marcial Resource Area, from which underground drilling is planned to expand the high-grade portions of the resource down dip. The Company recently discovered additional mineralization in the footwall, outside of the existing resource, and will also be drilling this area. GR Silver Mining is the first company to conduct exploration at San Marcial in over 10 years. The NI 43-101 resource estimate (San Marcial Project – Resource Estimation and Technical Report) was completed by WSP Canada Inc. on March 18, 2019 and amended on June 10, 2020.
Recent exploration has identified silver and gold mineralization in areas previously defined as non-mineralized, discovering evidence of pervasively altered rocks with intense silicification, veining and associated wide, silver and gold mineralized zones on the footwall of the NI 43-101 resource.
Plomosas and San Marcial collectively represent a geological setting resembling the multimillion-ounce San Dimas Mining District which has historically produced more than 600 Moz silver and 11 Moz gold over a period of more than 100 years.
GR Silver Mining’s other projects are situated in areas attractive for future discoveries and development in the same vicinity of Plomosas and San Marcial in the Rosario Mining District.