Mountain Boy's Theia Project in the Golden Triangle
15th July 2021
The Golden Triangle in British Columbia, Canada, is rightly known for the richness of its mineral deposits, especially gold and copper, and it has attracted a large amount of exploration attention over the last decade or so. One of the companies leading the charge to uncover more wealth in the mountains is Spotlight sponsor Mountain Boy Minerals (TSXV:MTB). This busy junior has six active exploration properties in the region, including their flagship American Creek project, which is centred on the historic Mountain Boy silver mine. Another prospect has caught our attention here at Spotlight, though: the multi-element Theia project, located 30 kilometres from the local mining hub of Stewart.
The geology of Theia is complex, with the area having undergone a long history of deformation and intrusion. The surface rocks belong to the Hazelton Group, a 300 km wide collection of sedimentary and volcanic rocks that are postulated to have formed as a joint back arc basin shared by two separate volcanic arcs, which formed on the Stikine Terrane of the Canadian Cordillera about 205 Ma ago, before it was accreted. The trough between them underwent extension during the deposition of the Hazelton Group, as tectonic plates subducted from either side under the microcontinent of Stikinia. Some of the regional deposits, namely the porphyry-Cu type, are linked to this era in the area’s history, with the working hypothesis being that subduction-related metalliferous magmas underplated Stikinia, leading to the ascent of fluids bearing mostly base metals. Indeed, the first phase of exploration on Theia, in 1967, was looking for a molybdenum porphyry deposit that could have been related to this process. Later, at about 174 Ma ago, rifting occurred in the area as Stikinia collided with other terranes during orogenic episodes, and this led to the creation of VMS style deposits in the region. After accreting, the region was deformed by compression, leading to the Skeena fold and thrust belt that represents much of the area’s considerable shortening.
The diversity of potential targets at Theia is one thing that makes the project special. The exploration work begun in 1967 was looking at an intrusion that had returned anomalous lead, zinc and molybdenum values, and since then other campaigns have broadened the scope of exploration. In the 1990s, work began again with a focus on precious metals. A sheared contact between sediments and a granodiorite intrusion gave samples up to 6.40 g/t gold, and 3.52 g/t Au from within the granodiorite itself. Two veins sampled in 1996 showed up to 526.6 g/t of silver. Quartz veins in the northern portion of the project vary in size from a few centimetres to metres in width, and are known to pinch and swell over strike. While these veins are often barren, this is not always the case and one grab sample in particular has a very diverse range of mineralisation; it showed 0.62 g/t gold, 522 g/t silver, 0.13% lead, 2.65% copper and 0.14% zinc. This sample had coarse blebs of tetrahedrite, an important copper and silver ore, and intense staining from malachite, azurite and iron oxide alteration. It certainly must have been an attractive sample in hand specimen.
Silt sampling during the same era in Ohl Creek in the eastern part of Theia focused on an area close to the contact between the Hazelton Group and a large granodiorite pluton. These river samples produced consistently highly anomalous gold readings, as well as scattered anomalous readings for silver, copper, lead and zinc. On sample graded at an impressive 9.48 g/t Au and 12.8 g/t Ag. Work in 1994 and 1996 uncovered polymetallic quartz veins north of White River, the best of which gave results of 24.914 g/t Au, 1254.0 g/t Ag, 123 g/t Mo, 31.45% Pb and 10.10% zinc, which is truly stunning. Not to be left out, the western extent of the project contains massive stringers of sulphides, as well as sulphides in quartz lenses filling shear zones in the local rhyolite. Clearly, Theia is a property with more exploration potential even than other projects in the famous Golden Triangle.
Mountain Boy is working actively to characterise this intriguing property. They have an exploration campaign currently ongoing which will include re-interpretation of previous VTEM, detailed mapping, sampling and channel sampling. One advantage that this team will have over those that worked here in the 1990s is that the glaciers on the property have retreated significantly since then, which has exposed fresh land and outcrop for exploration. Mountain Boy’s work on the property last year confirmed the historical high-grade silver showings, and extended the mineralised trend to 500 m, well above the earlier reports. Recent grab samples have returned truly astonishing numbers, especially for silver, with one showing 39 kg/t Ag, 3.45 g/t Au, 45.8% Pb, 1.25% Cu and 2.57% Zn, with another giving results of 1.68 kg/t Ag, 3.46% Pb and 2.7$ Zn. Grab samples are, of course, selective by nature but nevertheless these are the kinds of numbers any company would be happy to see. The current exploration program is designed to identify targets for future drilling, whose results will be fascinating to see.
As it stands, Theia represents just one of six projects under active exploration by Mountain Boy. This makes it part of a stable of properties representing virtually every mineralisation type that the Golden Triangle has to offer; VMS, epithermal, porphyry and shear zone deposits covering a wide range of base and precious metals. Their geology team is led by Lucia Theny, with years of experience in British Columbian exploration, and it therefore seems that Theia, along with other Mountain Boy projects, are in the right hands to identify any economic deposits they might have to show.