Thorn Project Summary
Brixton’s 100% owned Thorn project hosts a district scale Triassic to Cretaceous volcanoplutonic complex and related sedimentary units with several styles of mineralization related to porphyry and epithermal environments. Targets include sediment hosted gold, high-grade silver-gold-lead-zinc-bearing diatreme-breccia zones, high sulphidation gold-silver-copper breccia-veins and dissemination porphyry copper-gold-silver.
The 996 sq. km Thorn Project is located in the Sutlahine River area of northwestern British Columbia, Canada, approximately 105 km ENE from Juneau, AK.
Thorn is relatively accessible from Vancouver. A commercial flight to Whitehorse, Yukon departing in the morning allows for transfers to a small fixed wing aircraft which can land on the airstrip at the property by lunch time.
Brixton Metals Corporation wholly owns the Thorn claim group and is subject to net smelter royalties (NSR) that range from 0% to 3.5% to some of the original property vendors. The NSRs have buy down clauses to 1.5%.
The earliest known work on the Thorn property was carried out by Kennco Explorations (Western) Limited in 1959 during a regional exploration program. Including work by Brixton a total 323 silts, 5,194 soils, 1,321 rocks samples were collected. Geophysical work included ground magnetics, IP, airborne VTEM, and magnetics. The total drilling to date is 21,327m within 155 holes property wide.
Brixton carried out several exploration programs since it acquired the project in 2010 from Rimfire Minerals (now Kiska Metals, which was recently acquired by AuRico Metals).
Geology hosts a district scale Triassic to Cretaceous volcano-plutonic complex with several styles of mineralization related to porphyry and epithermal environments. Targets include sediment hosted gold, high-grade silver-gold-lead-zinc-bearing diatreme-breccia zones, high-grade gold-silver-copper veins and porphyry copper-gold-silver.
The area northwest of the Sutlahine River is underlain by mafic volcanic and marine sedimentary rocks of the Triassic Stuhini Group and lesser coarse clastic strata of the Jurassic Laberge Group, which strike northwesterly and dip steeply to the northeast (Awmack, 2011). These are cut by quartz feldspar and feldspar porphyry intrusions that are generally elongated NW-SE (Chapman, 1991). These are attributed to the Thorn suite based on lithological similarities (Awmack, 2011). The area southeast of the Sutlahine River is more complex. Stuhini Group volcanic rocks comprise much of the area southwest of La Jaune Creek, with only a small amount of Stuhini Group clastic strata present immediately adjacent to the creek. Stuhini Group strata continue East of La Jaune Creek to the vicinity of the Outlaw Zone where they are overlain by 5-20 m of limestone and undifferentiated clastic strata, including a boulder conglomerate, all assigned to the Sinwa Formation (Simmons et al., 2005). The Sinwa Formation is overlain by the Laberge Group, which is locally represented by coarse clastic strata assigned to the Takwahoni Formation (Awmack, 2011). These strata form a moderately north plunging anticline. Several rhyodacite dykes intrude this sequence and have been dated at 168.1±0.7 Ma, leading to them being assigned to the Fourth of July suite (Simmons, 2005). Immediately northeast of La Jaune Creek is the 93.3±2.4 Ma (Mihalynuk et al., 2003) Thorn Stock quartz feldspar porphyry; the main host to mineralization at the Oban breccia, Taliker and Glenfiddich Zones. The Thorn Stock is nonconformably overlain by the dominantly felsic, subaerial Windy Table volcanic rocks that generally dip shallowly to the north. Several intrusive bodies assigned to the Cretaceous (Cirque Monzonite, Son of Cirque Stock, and Outlaw monzonite-granodiorite) are roughly located along the boundary between Cretaceous and older strata. Two new diorite plugs were mapped in 2016 in the Chivas area are of unknown age. A second unconformity known as the Redline, as further described below, is mapped related to the Outlaw and Chivas Zones.
Jeff Kyba and Joanne Nelson, Northwest Regional Geologist for the British Columbia government: ” BC Survey’s ‘red-line’ a game changer for explorers. Northern Miner, May 6, 2015.” http://www.northernminer.com/news/bcgs-presents-a-big-game-changer-for-explorers-in-nw-stikine/1003601910/?&er=NA#sthash.8QptB20p.dpuf
Kyba has suggested that the geological contact between Triassic age Stuhini rocks and younger Jurassic age rocks is an important marker for finding large-scale mineral deposits. Geologists Jeff Kyba and Joanne Nelson from the B.C. Geological Survey may have unlocked the secret to world-class porphyry- and intrusion-related gold-copper deposits in northwestern B.C. They’ve discovered that most of the major deposits in the region occur within 2 km of a regional stratigraphic contact.
The rocks on the property have been structurally well prepared for mineralizing fluids. All structures on the Thorn Property are interpreted by SRK to be the result of a single D1 event characterized by NE-SW oriented maximum shortening. Under such a regime the N-S dextral faults are the master faults with NNE-SSW set representing P (synthetic) shears, NE-SW set representing R (synthetic) shears, E-W representing P’ (antithetic) shears, and NW-SE set representing R’ (antithetic) shears. Synthetic shears have the same sense of motion as the master fault, whereas antithetic ones have the opposite sense. Outcrop scale representations of this fault geometry were observed on the property. The maximum extension direction is NW-SE, leading to tensional veins striking NE-SW as has been observed for many of the high sulphidation veins on the Thorn Property. However, these veins vary from NE-SW to NNE-SSW and field observations suggest that many of them are fault-fill veins. It is therefore interpreted that they formed as a combination of tensional veins and fault fill veins along the favourably oriented R and, to a lesser extent, P shears.