Drilling and field work along the Scarlet-Tarn Trend (Figure 1) found zones of intense stockwork and replacement-style VMS mineralization associated with east-west trending andesite dikes interpreted to have been emplaced along syn-volcanic VMS feeder structures. In the broader context of the Scarlet-Tarn trend, hydrothermal alteration and precious metal concentrations intensify southwards from Scarlet Ridge towards Tarn Lake. These observations suggest that Scarlet Ridge and Scarlet Valley are distal components of a VMS system centered around the Tarn Lake and Scarlet Knob area. As with the Eskay anticline trend of VMS systems to the west, VMS mineralization on the Scarlet-Tarn trend occurs around distinct volcanic centers separated by ~1 km from each other, focused around east-west trending andesite dikes. The association of sulfide mineralization and hydrothermal alteration with the dikes is strong evidence supporting the presence of several syn-volcanic VMS feeder structures along the Scarlet-Tarn trend.
Figure 1: Geological map showing the Eskay anticline and Scarlet-Tarn trends of VMS mineralization. Geological mapping of the Scarlet-Tarn trend by Eskay’s team in 2022 has determined that the stratigraphic younging direction is to the west, and that the Eskay rhyolite host to mineralization at Tarn Lake is overlain by Willow Ridge basalt to the west. The contact between these two lithologies define the Contact mudstone horizon, the host to the world-class mineralization at Eskay Creek mine. This finding is a significant step towards our goal of finding Eskay Creek-like VMS deposits.
Tarn Lake and Scarlet Knob
The Tarn Lake and Scarlet Knob targets are extensive zones of polymetallic sulfide mineralization hosted by intensely altered and gossanous Eskay rhyolite (Figure 2), the same host rock as the world-class Eskay Creek deposit ~7 km to the northwest. Mineralization is focused along east-west trending andesite dikes, and is polymetallic with pyrite, sphalerite, galena, and arsenopyrite occurring in Au and Ag enriched samples (Figures 2 and 3). Geologic mapping and rock chip sampling suggests that Tarn Lake and Scarlet Knob may be connected underneath Bruce Glacier (Figure 3), with high-grade rock chip samples extending up to the glacier margins.
Drilling at Tarn Lake intercepted long intervals of disseminated Au- and Ag-bearing replacement-style sulfide mineralization (Figures 4 and 5). The highest grades occurr in zones exhibiting the most intense replacement-style mineralization. Hydrothermal alteration at Tarn Lake and Scarlet Knob is very intense (Figure 6), and coincides with an east-west trending magnetic low (Figure 17) identified during the 2021 property-wide geophysical survey. Our interpretation is that this magnetic low is caused by destruction of magnetic minerals during hydrothermal alteration, and that it may help define the extent of the feeder zone for the Tarn Lake and Scarlet Knob VMS system. Similar, but smaller magnetic lows are associated with the feeder zones at Scarlet Valley and Scarlet Ridge (Figure 17).
Figure 2: Photos of spot rock chip samples and the field localities from which they were collected. The Tarn Lake sample (a & c) is hydrothermal breccia with high-grade gold (9.2 g/t Au) and was collected from a large >20 m high outcrop displaying abundant sulfide replacement and stockwork. Note, red arrow points to a geologist for scale. Similar rocks are observed ~850 m to the east at Scarlet Knob (b & d) where a stockwork feeder sample yielded precious metal concentrations of 56.9 g/t Au and 154 g/t Ag. At both locations, replacement and stockwork zones are spatially associated with Eskay rhyolite, a host to mineralization at the nearby Eskay Creek deposit.
Figure 3: Plan map showing distribution of Eskay rhyolite around Bruce Glacier at Tarn Lake – Scarlet Knob. Results for Au and Ag from spot rock chip samples collected in 2022 are shown along with legacy data from previous programs. A large proportion of the 2022 rock chip samples were collected from areas that were covered by glacial ice during the early 1990’s when much of the legacy rock chip sampling was conducted. Sulfide mineralization at Tarn Lake (west) and Scarlet Knob (east) show consistently elevated Au and Ag values. This includes a notable high-grade sample yielding 56.9 g/t Au and 154 g/t Ag along the eastern margin of Bruce Glacier, some 800m east of Tarn Lake. Given the east-west orientation of VMS feeder zones in the area, Eskay Mining thinks there is good potential that Au and Ag mineralization connects under Bruce forming a >1km corridor of precious metal-rich VMS mineralization.
Figure 4: Assay results in Au equivalent (Au+Ag/78) from the maiden drill program and rock chip sampling at Tarn Lake. The top figure is a map view showing the location of the 200 m thick cross-section C-C’ (along line 6273600 N) at bottom. Drill holes TN22-10, TN22-12, TN22-8, and TN22-6 define an 85 m long trend of Au mineralization along strike. Drilling combined with rock chip sampling indicate a west-dipping zone of mineralization extending from the surface ~75 down-dip. Mineralization is open down-dip. Eskay’s mapping team has determined that the stratigraphic younging direction is to the west. This, combined with the Au-bearing rock chip samples to the west indicate VMS mineralization continues up-stratigraphy towards the inferred upper contact of the Eskay rhyolite.
Figure 5: Close-up views of styles of sulfide mineralization in core from Tarn Lake. Top: semi-massive sulfide replacement of rhyolite breccia. Rhyolite fragments are intensely silicified and corroded along contacts with sulfide minerals. The highest-grade Au and Ag mineralization is associated with intense sulfide replacement. Bottom: A representative example of disseminated sulfide mineralization. Sulfide minerals variably fill vesicles and replace plagioclase phenocrysts within the rhyolite, creating a disseminated style of mineralization. Sulfide stockwork veins cut the rhyolite and often feed into sulfide disseminations. Disseminated sulfide mineralization is strongly anomalous with Au and Ag, and likely represent zones of weaker sulfide replacement of the rhyolite than the high-grade zones.
Figure 6: A set of 200 m thick cross-sections of Tarn Lake looking south, centered on line 6273600 N. Down-hole lithology is shown for the two left figures, and down-hole magnetic susceptibility on the figure on the right. Gold mineralized zones are shown as yellow and orange volumes, and hydrothermally altered zones as blue and pink volumes. Gold mineralization is closely associated with intensely altered Eskay rhyolite, with Ishikawa alteration indices greater than 85 indicating close proximity to a VMS feeder zone. These results support our interpretation that the east-west trending andesite dikes were emplaced along syn-volcanic VMS feeder structures. Magnetic susceptibility is relatively low, and is consistent with the airborne magnetic survey showing a pronounced east-west trending magnetic low extending from Scarlet Knob to Tarn Lake.
Scarlet Valley
Scarlet Valley lies ~1 km north of Scarlet Knob, and is characterized by a large gossanous outcrop (Figure 7) of stockwork sulfide mineralization hosted proximal to the contact between rhyolite-bearing volcaniclastic debris flows and cross-cutting andesite east-west trending dikes. Sulfide veins on the surface yielded several Au- and Ag-bearing samples (Figure 8). Drilling intercepted tens of meters of sulfide mineralized rock with highly anomalous Au and Ag values with higher grade pockets associated with the most intense hydrothermal alteration (Figures 9-11).
As with the other VMS systems along the Scarlet-Tarn trend, andesite dikes at Scarlet Valley are interpreted to have been emplaced along syn-volcanic VMS feeder structures. The association of mineralization and moderate hydrothermal alteration with the dike contacts (Figures 10 and 11) support this interpretation.
Figure 7: Mineralized rhyolite-bearing debris flow breccia targeted by the maiden drill program at Scarlet Valley. Mineralization is stockwork- and replacement-style, and is focused along east-west trending andesite dikes. Hydrothermal alteration is less intense at Scarlet Valley than at Tarn Lake, but more intense than at Scarlet Ridge, indicating a weakening of hydrothermal alteration to the north of Tarn Lake.
Figure 8: Plan map of the Scarlet Valley area displaying the distribution of exposed gossans and Eskay rhyolite along with the drill traces and a zone of anomalous gold identified from the drilling results. These anomalous Au and Ag occur proximal to the stratigraphic level of the Eskay rhyolite.
Figure 9: Assay results for drill core intercepts and rock chip samples from Scarlet Valley. The figure at top is a plan view, and the figure on the bottom is a cross section centered on line 6274900N looking south. Stockwork and replacement style sulfide mineralization is focused along the contacts between east-west trending andesite dikes and volcaniclastic debris flows.
Figure 10: Representative drill core from Scarlet Valley. The top image shows stockwork- and replacement-style pyrite mineralization hosted along the margins of an andesite dike. The bottom image shows pyrite infilling the matrix of a polymict rhyolite clast-bearing volcaniclastic debris flow breccia. The presence of rhyolite places rocks at Scarlet Valley in the upper Hazelton Group. Precious metals occur with the brighter yellow pyrite, and are absent from the dull brown pyrite.
Figure 11: A set of 250 m thick cross-sections of Scarlet Valley looking south, centered on line 6274900 N. Down-hole lithology is shown for the two left figures, and down-hole magnetic susceptibility on the figure on the right. Gold mineralized zones are shown as orange volumes, and hydrothermally altered zones as purple and blue volumes. Gold mineralization is relatively weak, focused along the contact between andesite feeder dikes and volcaniclastic debris flow deposits. Mineralization is closely associated with moderate hydrothermal alteration, with Ishikawa alteration indices of ~ 75 indicating a more distal relation to the hydrothermal center than Tarn Lake.
Scarlet Ridge
Sulfide mineralization at Scarlet Ridge is dominantly stockwork-style, and is focused along east-west trending andesite dikes (Figure 12), and is hosted by perlitic andesite and peperitic dacite breccia that is gossanous on the surface (Figures 13 and 15). Precious metal mineralization is heterogeneous, with rock chip sampling indicating widespread Au and Ag anomalism (Figure 14). Drilling intercepted tens of meters of stockwork sulfide mineralization, however appreciable Au and Ag grades are restricted to the top 30 m of drill holes SR22-1, SR22-2, and SR22-3. Hydrothermal alteration is weak (Figure 16), and is indicative of a distal position with respect to the core of the VMS feeder system interpreted to be located at Tarn Lake. As is the case with Tarn Lake and Scarlet Valley, stockwork mineralization at Scarlet Ridge is associated with an east-west trending magnetic low, suggesting magnetite destruction during hydrothermal alteration (Figure 17).
Figure 12: Examples of stockwork and replacement-style sulfide mineralization at Scarlet Ridge. Stockwork mineralization at Scarlet Ridge and along the greater Scarlet-Tarn trend is focused along, and generally parallel to the contacts between east-west trending andesite dikes and the surrounding rock. These relationships support the interpretation that the east-west trending andesite dikes were emplaced along syn-volcanic VMS feeder structures.
Figure 13: Plan map of the Scarlet Ridge area showing the mineralized gossanous debris flow breccia that was targeted by drilling. Drill traces are shown in red.
Figure 14: Assay results for drill core intercepts and rock chip samples from Scarlet Ridge. Top is a plan view, and bottom is a cross sectional view looking south. Stockwork and replacement style sulfide mineralization is focused along east-west trending andesite dikes, and is not as extensive as at Scarlet Valley or Tarn Lake.
Figure 15: Representative drill core from Scarlet Ridge. Sulfide mineralization is dominantly replacement style, replacing and andesite dike (top image), and along fractures within perlitic andesites (bottom three images). Pyrite mineralization is intense; however, the Ishikawa alteration indices are relatively low at Scarlet Ridge, indicating a distal position with respect to the VMS hydrothermal center.
Figure 16: A set of 400 m thick cross-sections of Scarlet Ridge looking north centered on line 6275800 N. Precious metal mineralization is localized to a zone near the collars of drill holes SR22-1, SR22-2, and SR22-3. Hydrothermal alteration is weak, and is associated with Au-Ag mineralization. Magnetic susceptibilities are relatively high, and are consistent with weak alteration of the host andesite, dacite, and sedimentary rocks.
Figure 17: Magnetic tilt derivative map (top), and 3D model of the 0.001 SI magnetic susceptibility volume (bottom) for the Scarlet-Tarn and Eskay Creek-Lulu trends. Rock chip assay results from Eskay Creek were obtained from assessment reports in the public domain. As with the other VMS systems described in this release, those on the Scarlet-Tarn trend are associated with low-amplitude magnetic anomalies evident when a tilt derivative is applied to the data and occur along the margins of protrusions in the 0.001 SI magnetic susceptibility volume. Tarn Lake and Scarlet Knob are associated with a zone of low magnetism (black dashed ellipse) interpreted to be caused by destruction of magnetic minerals during intense hydrothermal alteration. This east-west trending corridor of low magnetism coincides with the inferred trend of mineralization that may link Tarn Lake and Scarlet Knob. Exploration of all the anomalies on the Scarlet-Tarn trend will continue in 2023 with an extensive soil, rock chip, and channel sampling program. The trend of magnetic susceptibility anomalies immediately west of Tarn Lake lie up stratigraphic section and may lie near the inferred Contact Mudstone Horizon. Testing for extensions of the Tarn Lake-Scarlet Knob system will be a major focus of drilling in 2023.