The Chivas area is underlain by volcanic rock of the Upper Triassic Stuhini Group which are intruded to the north by a feldspar porphyry stock (the Thorn Stock) of the Windy Table Complex and to the west by an alkali feldspar granite batholith of the Paleocene to Eocene Sloko-Hyder Plutonic Suite batholith. The Chivas area is notable for large gossanous cliffs and scree slopes. It is dominated by Triassic Stuhini Group volcanic and massive-to fragmental volcaniclastic lithologies, all of which are locally intercalated on all levels. The Stuhini mafic lithologies are intruded by at least four phases of feldspar porphyry, as well as local gabbroic intrusions, and mafic and felsic dikes.
The Chivas zone was first identified and sampled in 2014 by a single 700-metre soil line which yielded up to 11 parts per million gold (Assessment Report 34506). The Chivas zone is now considered as a broad gold-in-soil anomaly approximately 3.5 kilometres long and up to 2 kilometres wide that remains open in several directions. The area is underlain by the favourable Stuhini Group volcanic rocks and is proximal to the unconformity separating Jurassic clastic sediments from Upper Stuhini Group volcanic rocks. Anomalous soils previously collected have a strong gold-silver-tellurium-copper-molybdenum signature and have yielded values of 16.7 grams per tonne gold (Assessment Report 36638).
During the 2016 exploration program, geological mapping approximately 800 metres west of the Chivas soil anomaly identified the contact between Stuhini Group volcanic rocks and Jurassic Laberge siliciclastic sediments. Along this contact, Stuhini Group volcanic rocks consist of pillowed basalt grading upwards into pillow breccia. The Laberge Group sediments near the contact consist of heterolithic pebble conglomerate grading upwards into granule conglomerate, lithic sandstone, and wacke. This contact may correlate with the “red-line boundary” a regional stratigraphic marker for major regional-scale faulting which acted as a metal-rich fluid pathway.
A 2018 petrographic analysis of samples collected over the course of the study determined the presence of four distinct units within the Thorn Intrusive Suite: a fine-to-medium-grained, equigranular hornblende-diorite, as observed south of the main Chivas stock; a fine-grained and equigranular hornblende-biotite quartz monzodiorite that comprises the intrusive intervals observed at Outlaw (DDH: THN14-128); a crowded porphyry from the Chivas Zone consisting of approximately 45 per cent tabular plagioclase with lesser hornblende, stacked biotite and minor quartz eyes embedded in an aplitic groundmass (DDH: THN17-149) and; quartz porphyry containing 2 to 4 per cent rounded to broken quartz phenocrysts in an altered feldspar-rich matrix, that make up the host rocks observed at Oban and Talisker, as well as a portion of the extensive Chivas stock.
Exploration at the Chivas Zone has identified several areas of structurally emplaced intermediate sulphidation epithermal-type gold mineralization. Low-grade (0.1 to 0.2 per cent) copper mineralization and large molybdenite geochemical anomalies suggest the potential for porphyry type copper mineralization at depth within or near to the feldspar porphyry intrusion.
Mineralization assemblages observed within the Chivas Zone can be subdivided into three groups, and are described below:
1) Disseminated pyrite and pyrite-bearing stringer veins. This assemblage is the most abundant mineralization style present at the Chivas Zone, and is observed in all Stuhini Group mafic volcanic lithologies. Stuhini rock units can host up to 15 per cent pyrite, present as disseminations, fracture-fills, aggregates, clots and veins. In zones of abundant disseminated pyrite, local pyrrhotite and chalcopyrite can be observed. In areas located near the main felsic porphyry intrusion, Stuhini rocks also exhibit abundant pyrite replacement, on the order of up to 40 per cent pyrite. These zones are characterized by bright orange-yellow gossans and contain abundant limonite and jarosite.
2) Vein-hosted polymetallic sulphide mineralization. Shear-hosted quartz veins and quartz plus/minus carbonate breccia systems, dominantly observed throughout the main carbonate breccia/replacement zone, host polymetallic sulphides in abundances of: 15 per cent galena, 5 per cent pyrite, 2 per cent chalcopyrite, 2 per cent sphalerite, 1 per cent tetrahedrite. In areas of shear-hosted carbonate plus/minus pyrite-rich veins and breccia systems, a relatively late pulse of quartz-sulphide veining tends to form as lenses along the outer margins of carbonate-filled shears.
3) Disseminated pyrite-chalcopyrite plus/minus polymetallic quartz stockwork veins. This mineralization style is the least abundant form observed at the surface and is associated with the main felsic porphyry intrusion. It is confined to a 75-metre-wide northwest-southeast trending corridor centered along the main intrusion and is appears spatially related to the alteration zonation observed within the Chivas Zone. These veins generally contain pyrite-chalcopyrite with minor, less than 1 per cent combined sphalerite-galena-tetrahedrite, with fine-grained granular quartz that forms less than 5 millimetres wide veins with densities of up to 40 veins per metre.
At the Chivas Zone, Stuhini Group mafic volcanic lithologies exhibit early propylitic alteration consisting of pervasive chlorite plus/minus epidote plus/minus hematite that pre-dates a structurally controlled carbonate plus/minus quartz plus/minus pyrite dominated alteration assemblage, locally associated with polymetallic mineralization. Alteration observed within the Chivas Zone is well zoned in relation to a feldspar porphyry lithology (stock), as well as a fine-grained felsic intrusive phase approximately equivalent in composition. Isolated patches of quartz-sericite-pyrite, and weak sericite-pyrite, zones spanning a few tens of metres in size are observable within the main felsic stock. Locally, this alteration style is also present in the adjacent Stuhini host rocks. Minor silicified zones, locally associated with illite-sericite alteration accompany coarse-grained quartz veins and stockwork zones hosted within, and proximal to, the feldspar porphyry stock. A zone of chlorite-epidote, with more localized potassic and carbonate alteration, and hematite veinlets and fracture filling, extends outwards from the main intrusion on the order of 200 to 300 metres. Carbonate alteration observed in these zones is also locally concentrated within an extensive, northeast-southwest-to-dominantly north-northwest south-southeast trending carbonate breccia/replacement zone that has a mapped extension of 1200 metres throughout the western portion of the Chivas Zone. Here, host rocks are intensely brecciated, infilled, and completely replaced by carbonate. Overall, ankerite is the dominant carbonate mineral observed at the Chivas Zone, with lesser calcite and locally abundant pyrolusite. Isolated patches of quartz-sericite-pyrite, and weak sericite-pyrite, zones spanning a few tens of metres in size are observable within the main felsic stock. Beyond the main carbonate trend, carbonate-rich alteration zones are also associated with carbonate plus/minus quartz plus/minus barite filled shears. These alteration zones appear spatially related to the main carbonate breccia/replacement zone and appear to overprint the early propylitic alteration zones predominantly affecting older Stuhini mafic volcanic rocks.
Drill hole THN17-142 intersected two mineralized zones: an upper zone which returned a weighted average of 21.00 metres of 0.46 gram per tonne gold and 39.74 grams per tonne silver; and a lower zone that intersected 18.00 metres of 0.99 gram per tonne gold, 19.46 grams per tonne silver, 0.66 per cent zinc, 0.19 per cent lead (Assessment Report 36829). This lower interval included 6.45 metres of 2.63 grams per tonne gold, 45.15 grams per tonne silver, 1.5 per cent zinc, 0.18 per cent copper and 0.42 per cent lead (Assessment Report 36829).
Drill core relogging by the MDRU in 2018 indicated that most of the Chivas Zone drilled is dominated by widespread propylitic alteration that is locally overprinted by structurally controlled epithermal alteration. Overall, the porphyry mineralization and alteration were found to be subtle at Chivas whereas the epithermal mineralization is obvious and pronounced, in part because of its carbonate alteration and orange weathering.
WORK HISTORY
In 2016, Brixton Metals carried out a two-phase exploration program at the Thorn Property. During this time, 2303 soil samples and 247 rock samples were collected, a 15.49 line-kilometre Titan-24 DCIP geophysical survey was conducted over the area of the new Chivas Zone, and 9 diamond drill holes were drilled at the Outlaw and Aberlour Zones, totalling 1,644.91 metres (Assessment Report 36638). At the Chivas Zone, a new gold-in-soil anomaly was identified and corresponded with a near surface IP chargeability high, measuring 3.5 kilometres long and 1.9 kilometres wide, and remains open (Assessment Report 36638).
In 2017, the Brixton Metals Corporation exploration program on its Thorn property consisted of 2455 metres diamond drilling in 10 holes, the collection of 517 soil and 56 rock samples, a 176.60 square-kilometre aerial Lidar geophysical survey and detailed geological and alteration mapping at a 1:2,500 scale. All drill holes targeted the Chivas zone. The majority of rock and soil samples were collected from the Chivas Zone. Some rock and soil samples were also collected at the Cirque Zone, as well as in unexplored areas located north of the Sutlahine River, and northeast and south of the Chivas Zone.
In 2017, mapping by Brixton Metals delineated a new 1.2-kilometre-long copper corridor at the Chivas Zone, oriented along the center of an extensive feldspar porphyry intrusion, that remains open and untested by drilling. Brixton established a new copper-in-soil anomaly at the Chivas Zone, measuring approximately 2 kilometres in length. They identified multiple, structurally controlled, polyphase mineralization assemblages and veins at the Chivas zone. They identified multiple gold-silver-bearing zones hosted within Stuhini Group mafic volcanic and volcaniclastic lithologies, and locally proximal to the contact with phases of the main feldspar porphyry intrusion.
In 2018, small geochemical sampling surveys were carried out over areas of the Chivas, Outlaw, Glenfiddich and Talisker Zones, in an area termed the “Oban-Outlaw soil anomaly” and along Cirque Creek. Rock and soil samples were collected in each area to test or extend previously discovered geochemical anomalies in each area. Petrochemical, mineralogical and alteration studies were carried out in order to assess the district-scale mineralization styles and metal zoning patterns at the Thorn Property and to investigate the characteristics of the Chivas Zone in terms of porphyry-style mineralization and alteration. The Mineral Deposit Research Unit (MDRU) at the University of British Columbia carried out a detailed study on the Chivas Zone in 2018. This study involved: relogging of 6 drill holes from the Chivas Zone (drilled in 2017) and the collection of 389 drill core samples.
In 2018, 28 soil samples were collected from the Chivas and Chivas South Zones (Assessment Report 38219). Samples were commonly collected between 25- and 50-metre intervals along ridgeline contours. The max-min values from the 28 soil samples collected in 2018 for gold are 5 parts per billion and 2100 parts per billion, and 80 parts per billion to 1870 parts per billion for silver. The median value for gold is 20 parts per billion and 220 parts per billion for silver. 1 soil sample returned values greater than 1000 parts per billion gold, 3 greater than 100 parts per billion gold, 5 greater than 50 parts per billion gold and 10 greater than 30 parts per billion gold. The most impressive soil sample of 2018 was collected from the Chivas South Zone and returned assay values of 2100 parts per billion gold, 970 parts per billion silver, 1070 parts per million arsenic, and 108.5 parts per million copper. The Chivas South zone is 4 kilometres south of the Chivas zone and was assigned its own MINFILE number.
In 2020, Brixton Metals Corporation completed a program of geochemical (rock and soil) sampling, a 12.5 line-kilometre ground induced polarization survey, a 715 line-kilometre airborne magnetic and electromagnetic survey and 19 diamond drill holes, totalling 5292 metres, on the area of as part of the Thorn property. Drilling was performed on the Outlaw (MINFILE 104K 176) occurrence area.
Refer to Thorn (MINFILE 104K 031), Outlaw (MINFILE 104K 083) and Oban (104K 168) for details of a common work history and geological setting.
