The HC showing area occurs at or just below the contact between Lower Jurassic Unuk River Formation and overlying Lower Jurassic Betty Creek Formation, both Hazelton Group (Open File 1991-21). Fossils found approximately 500 metres along strike to the northwest indicate a Hettangian to Sinemurian age for these rocks.
The HC Zone appears to be a complete precious metal-rich VHMS deposit in which the feeder vein system, the vent structures, and the sulphides in a restricted sedimentary basin had been intersected. All three zones of the HC deposit carry elevated values of gold. The feeder vein system also carries elevated silver and base metal (lead, zinc, copper) content.
The HC Zone shows elevated concentrations of gold, silver, antimony-sulfosalts hosted between a pervasively sericite-pyrite-chlorite altered volcaniclastic sequence (bimodal mafic-felsic affinity), and restricted sedimentary basins where mudstones host sulfide mineralization underlying stockwork base metal and precious metal veins. These characteristics are similar and unique to the nearby Eskay Creek deposit. The highest grade, and most continuous precious-metal mineralization within the HC Zone, occurs as an apparent stratabound zone at the contact of the footwall mudstone and the hydrothermally altered volcaniclastic sequence. This is interpreted as being the product of a mineralizing growth-graben fault, proximal to felsic flows, ash tuffs, and felsic conglomerates.
The Feeder Vein System: It is comprised of discordant veins hosted mainly in pervasively sericite-pyrite-chlorite altered volcaniclastic sequence. Two types of veins are recognized: silver dominant manganese-rich carbonates and sulphides (semi-massive yellow to light brown zoned sphalerite, galena, pyrite and minor chalcopyrite can add to greater than 50 per cent of the veins) and gold dominant chalcedonic quartz veins. Textures include those more typical of the epithermal suite (banded, crustiform, breccia/vein). One intersection yielded 55.1 grams per tonne gold over 4.53 metres (Press Release, Tudor Gold, September 15, 2017).
The Vent Structure: It is comprised of silica flooded and altered mudstone and volcanic conglomerates along with breccias and semi-massive sulphide replacements. Several stages of silica can be recognized cementing and replacing successive events of brecciation. Silica alteration occurs as silicification and chalcedonic silica, usually gray to bluish in color, obliterating previous textures. Pyrite and antimony-sulphosalts are the dominant sulphides as veinlets, stringers and semi-massive replacements. Stibnite, galena, sphalerite and arsenopyrite are also common in veinlets and disseminations. One intersection yielded 11.1 grams per tonne gold over 0.45 metre (Press Release, Tudor Gold, September 15, 2017).
The sulphides in Sedimentary Basins: Fine grained pyrite and antimony-sulphosalts have been identified as finely laminated sedimentary beds and patchy pyrite/quartz replacements within mudstones/siltstones in the proximity of the venting structures intersected in core, particularly around holes HC-17-01, 04, 05, 08, 10, 11 and 12 (as per visual inspection of the drill core). The mineralization appears to be hosted in the immediate contact of the underlying footwall mudstone unit and the upper altered volcaniclastic sequence. One intersection yielded 10.2 grams per tonne gold over 1 metre (Press Release, Tudor Gold, September 15, 2017).
The following description of 1990 work is slightly modified from Assessment Report 21318: HC (Mama Susu-B) "numerous boulders containing up to 60 to 70 per cent galena, 10 per cent stibnite, malachite-azurite and sphalerite occur over a talus covered area measuring approximately 50 by 20 metres. The mineralization is related to a 20-metre-wide shear zone developed in andesitic pyroclastics, a substantial portion of which have been almost totally replaced by sericite and quartz. This zone can be considered to be the northeast extension of the mineralization encountered in GR2 (104B 370). Talus cover in the area between GR2 and HC conceals any potential mineralization along the structure.
Results of 1990 work from this zone were like those in Mama Susu-A (GR2) with gold and silver assays of 0.207 ounce per ton and 100 ounce per ton (#34706) and 4.87 grams per tonne and 2849 grams per tonne (#34513) respectively. These were both float samples of massive sulphide material consisting predominantly of galena. Grab samples from outcrop include 1.54 grams per tonne gold and 283 grams per tonne silver (#34705) and 2.67 grams per tonne gold and 237 grams per tonne silver (#34514). Base metal assays were not as high as those from Mama Susu-A but are nonetheless significant. Sample #34706 contained the highest copper (0.78 per cent), lead (20.7 per cent), and zinc (1.06 per cent). Other values of significance are lead 10.9 per cent (#34513) and 3.99 per cent (#34514)."
In 2017, drill hole HC-17-11 yielded a 9.7 metre intersection (from 221.15 to 230 metres) grading 4.89 grams per tonne gold (Tudor Gold Corp., News Release, December 7, 2017). A drill hole (HC-17-13) intersection sample from the silver-(base metal) subzone yielded 1.65 metres (from 216.65 to 218.85 metres) grading 5.4 grams per tonne gold and 123.56 grams per tonne silver (Tudor Gold Corp., News Release, December 7, 2017).
In 1990, the exploration program on the Treaty Gossan was conducted on behalf of Tantalus Resources Ltd and Teuton Resource Corp. This consisted of grid establishment, detailed geological mapping, prospecting, geochemical rock and soil sampling and magnetic and electromagnetic geophysical surveys. An area of new showings comprising seven separate exposures on the GR2 claim was further examined. A small grid totalling 5.225-line kilometres, was emplaced over the showings to provide control for geological mapping, trenching and a UTEM geophysical survey, much of which was conducted over an icefield.
In 2017, Tudor Gold Corp conducted drill program on the HC that consisted of 17 drill holes totalling 5,401 meters. Drilling tested the mineralized strata-bound structure for a strike length of 400 meters and 400 meters down dip (still open at depth), and the vein system remains open to the north, south and at depth (Tudor Gold Corp., News Release, October 12, 2017).
The HC extension of the GR2 Zone was reported to have been discovered during the 2017 exploration program of Tudor Gold. However, the plotted location of the HC is coincident with the MINFILE occurrence Mama Susu-B showing first discovered and sampled in 1990.
The GR2/HC drill program augmented the previous drill holes in the zone and consisted of 17 drill holes totaling 5,401 meters in 2017. The program was designed with a maximum of 50 metre step-outs in the mineralized zone to prepare for a preliminary resource estimate.
The GR2 (104B 370)/HC (104B 371) zone appears to be a gold-rich possible VHMS deposit in which the feeder vein system and the stratabound lenses have been intersected. A later silver-(lead-zinc-antimony-copper) vein system was also found reactivating some of the previous structures in the same area where the HC extension is located. These veins are late in the formation and are hosted in the volcaniclastic sequence or in the younger Jurassic Hazelton sequence, crosscutting (and reactivating) previous HC related feeder vein system and HC stratabound lenses. The RR Ag-base metal vein holes are collared 800 metres north of the HC zone, following the same structure.
Thirty-six drill holes have been drilled to date in the GR2, covering an area approximately 400 metres along strike and 450 metres down dip at 50m space increments that show consistent geology, and which demonstrate the distribution and continuity of the feeder vein system, the strata-bound zone, and the late silver-base metal vein system. Historical surface sampling carried out by previous operators to both the north and south of the GR2/HC zone indicates that the main mineralized structure potentially extends 3,000m along strike. The mineralized structure remains open to the north and south beyond the existing drill holes, and down dip.
Refer to GR2 (104B 370) for details of related mineralization, history and bibliography. Also refer to Copper Belle (104B 518) for related Treaty Creek Property history and bibliography).