First Mining Expands and Advances High-Grade Gold Discovery at its Birch-Uchi Greenstone Belt Exploration Project

VANCOUVER, BC / ACCESSWIRE / September 9, 2024 / First Mining Gold Corp. ("First Mining" or the "Company")(TSX:FF)(OTCQX:FFMGF)(FRANKFURT:FMG) is pleased to announce new assay results for the Challenger high-grade gold discovery at the Company's Birch-Uchi Greenstone Belt Exploration Project ("BUGB Exploration Project" or the "Project") located in northwestern Ontario, Canada. The Challenger target area is located 12 km southwest of the First Mining's flagship Springpole Gold Project and has become one of several high priority exploration targets for the Company.

The 2024 follow-up field mapping program has yielded four new gold occurrences, including visible gold in grab and channel samples, that are proximal to the original 2023 discovery area. The new results also include detailed channel sampling across the discovery area with assay highlights of 6.53 g/t Au over 3 m (including 57.8 g/t Au over 0.3 m) and grab sample assays at the new outcrop sites of up to 26.6 g/t Au, 20.3 g/t Au, and 7.73 g/t Au. First Mining has now established a series of significant high-grade samples within additional outcrops that expand the mineralization footprint of the original discovery area (see news release dated December 5, 2023).

"We are extremely excited to be returning additional high-grade results and visible gold from our major discovery at the Challenger target hosted in the Red Lake Mining District and in very close proximity to our flagship Springpole Gold Project," stated Dan Wilton, CEO of First Mining Gold. "We fully believe that the endowment within our extensive Birch-Uchi Greenstone Exploration Project is at a stage where immense value in discovery can be realized through our value driven exploration efforts. While our Springpole Gold Project is well advanced in the environmental assessment process, these exploration efforts will continue to demonstrate district-scale potential around Springpole."

Challenger Target Highlights:

• Four newly discovered gold mineralization occurrences, including visible gold, in proximity to the Challenger discovery, with samples grading up to 26.60 g/t Au, 20.3 g/t Au and 7.73 g/t Au

• New channel sample results grading up to 6.53 g/t Au over 3 m (including 57.4 g/t Au over 0.3 m)

• Proximity to an expanding gold mineralization system identified in First Mining's 2023 winter drill program (Challenger is located 375 m northwest of the Saddle target), where Saddle drilling returned 0.92 g/t Au over 114 m (see news release dated July 6, 2023)

• Located within 12 km southwest of the Company's Springpole Gold Project

  

Figure 1: Challenger Discovery and Saddle Target Location, 12 km SW of the Springpole Gold Project

Table 1: Selected Rock Grab Sample Assays from the Challenger Target

Note: Rock grab samples are selective in nature and may not be indicative of the true grade and style of mineralization on the property. Coordinates are in UTM, WGS84 Zone15N.

Table 2: Selected Channel Sample Assays from the Challenger Target

Note: Channel samples are selective in nature and may not be indicative of the true grade, width and style of mineralization on the property

Challenger Target

The Challenger target is located approximately 12 km southwest of First Mining's Springpole Gold Project (see Figure 1), which hosts a NI 43-101 mineral resource of 151 million tonnes at 0.94 g/t Au, totalling 4.6 million ounces of gold in the Indicated category, and 16 million tonnes at 0.54 g/t Au, totalling 0.3 million ounces of gold in the Inferred category*. The Challenger target is hosted within the Company's BUGB Exploration Project, where locally a significantly deformed and mineralized granodiorite intrusive occurs in contact with clastic sedimentary turbidites and conglomerates. Mineralization identified to date is associated with a series of interpreted parallel zones of increased silica and carbonate-altered shear structures and is now seen to occur over an expanded area of approximately 200 x 600 metres, with high concentrations of multiphase quartz veining within a thick bedded turbidite sequence. The dominant sulphide mineralization is composed of pyrite and occurs as very fine-grained disseminations averaging an abundance of 1-5%. At least two generations of quartz veining are documented subparallel and orthogonal to the controlling structure and vary from 1 cm to 50 cm in scale. Mineralization is coincident with geophysical resistivity low signatures interpreted to be associated with large-scale folding and associated deformation within the clastic sedimentary lithology. The 2024 field results indicate that several high-grade mineralized structures exist, with an open opportunity for further expansion and characterization with additional exploration work including diamond drilling.

* Details of the Springpole Gold Project mineral resource can be found in the technical report entitled "NI 43-101 Technical Report and Pre-Feasibility Study on the Springpole Gold Project, Ontario, Canada" which was prepared by AGP Mining Consultants Inc. in accordance with National Instrument 43-101 Standards of Disclosure for Mineral Projects ("NI 43-101") and has an effective date of January 20, 2021.

2024 Challenger Summer Field Campaign

The 2024 summer field campaign for the Challenger area focused on mineralization expansion and characterization of the discovery area with a specific emphasis on mapping and prospecting, channel sampling and soil geochemistry programs. First Mining's exploration teams this year completed 8 km of mapping transects, 9 channel samples, 59 grab samples, and 289 soil samples across the area to enhance the local and regional data resolution and geological understanding of this underexplored area.

Results of the 2024 Challenger target follow-up exploration program were successful in further expanding the mineralization along strike, with newly discovered mineralized outcrops to the west and southwest, supporting efforts in building up the geological understanding of the setting and controls on mineralization. The most westerly outcrop discovered returned visible gold in sample C261094 (Figure 2) and validated a further 40 m westerly strike extension from the second Challenger extension outcrop which returned 7.1 g/t Au in the 2023 program and which was already a 60 m extension from the initial 2023 Challenger discovery outcrop which returned 25.6 g/t Au (Figure 3). This latest western extension was channel sampled (SAT24C-001) and returned assays of 2.17 g/t Au over 1.7 m, including 0.4 m at 4.65 g/t Au, expanding the current established surface strike extent to 100 m (Figures 3, 4).

Figure 2: Photos Showing Visible Gold in Grab Samples at the Challenger Target

Figure 3: Grab Sample Highlights from the 2023-2024 Programs in the Saddle-Challenger Target Areas

Additional highlights from the Challenger target channel sampling program are SAT24C-002 returning 2.57 g/t Au over 1.7 m, including 3.81 g/t Au over 1 m, and SAT24C-003 returning 6.53 g/t Au over 3 m, including 57.80 g/t Au over 0.3 m from the silica-ankerite altered sheared structure with its two distinct quartz vein generations (Figure 4).

Figure 4: Example of the Detailed Outcrop Mapping at the Challenger Target, including Channel Sample Locations

Additional mineralized outcrops were identified 75 m to the southwest of the Challenger discovery target, returning up to 26.6 g/t Au in grab sample C262506, including visible gold (Figure 3).

A new area of gold mineralization was identified between Challenger and Saddle and initial data supports this to be a third interpreted trend ("Charger") for further exploration advancement. Initial results from the Charger target trend returned up to 20.3 g/t Au in grab sample C262511 and 3.76 g/t Au in grab sample C262513, approximately 300 m towards the southwest of the Challenger discovery outcrop. Additional supporting grab samples include 7.73 g/t Au (C262637) and a 1.67 g/t Au grab sample (C262636), located approximately 165 m to the south of Challenger. There is an estimated 270 m distance between the two sample locations that remains open for exploration continuity. The Charger target is interpreted to be a parallel trend to the original Challenger discovery (Figure 5).

Figure 5: Location Map of Main Targets Saddle and Challenger, including Charger Trend and Greencamp

The geoscience data around the Challenger target and Charger target trend highlights the importance of the relationships between the surface mineralization, shear structures and an alteration expression that is coincident with a series of resistivity low signatures. Mapping campaigns have further enhanced the structural interpretation supporting the delineation of key fold structures, which are shallowly plunging towards the west along the trends of mineralization (Figure 3). Early indications support that the target area's mineralization trends coincide with axial planar mapped fold structures, which are within clastic sedimentary units. By recognizing these relationships, exploration efforts are being more directed and focused on areas for favourable gold endowment.

Throughout the remainder of the 2024 program, exploration campaigns will be focused on completing final transects, reviewing assay data which is still pending from an infill soil geochemical survey, and updating interpretations for target model development and forward drill planning for this area.

"Unlocking new discoveries is a fundamental objective for our exploration teams in their efforts to advance a pipeline of prospective targets within the Company's 70,000-hectare Birch-Uchi Greenstone Exploration Belt Project and Springpole Gold Project," stated James Maxwell, VP Exploration and Project Operations for First Mining Gold. "We look forward to providing additional updates on our regional exploration efforts where a number of high priority targets are gaining momentum."

All assay results from the Challenger target grab and channel sample program are reported below in Table 3 and Table 4 which includes sample location data.

Table 3: Complete Grab Sample Assay Results at the Challenger and Saddle Target Areas