The Harper Creek (Yellowhead Copper) deposit lies 3500 metres north of the Cretaceous Baldy batholith and within metavolcanics and metasediments of the Lower Cambrian and older(?) to Mississippian Eagle Bay Formation.

Regionally, the occurrence is located on the western margin of the Omineca Belt, in the Kootenay Terrane, in the metamorphic rocks of the Eagle Bay Assemblage and the Fennell Formation. The assemblage containing the occurrence is bordered by high grade metamorphic rocks of the Shuswap Complex to the east, and rocks of the Intermontane Belt to the west. The Quesnel Terrane, a Late Triassic to Early Jurassic magmatic arc is situated to the west of the area adding complexity to the structure and lithologies. The occurrence lies in the region of the Cretaceous Bayonne plutonic belt, split into the northern Raft batholith and the southern Baldy batholith, adding further lithologic, and structural complexities.

Local geology is summarized as a series of intrusive suites, in a number of discordant and sub-concordant dikes, sills, and larger intrustives. Exploration work in 2011 reidentified local lithologies apparent ages that were previously identified as siliceous, sericite-quartz, and/or chlorite-sericite-quartz phyllites and schists, considered to be part of Devonian Eagle Bay volcanic association. It may be dikes or gently dipping tabular plugs rather than intrusions into the Devonian Eagle Bay. This observation suggests the intrusives in the region are post-Devonian to pre-Cretaceous in age. The new defined lithologies are summarized into categories from apparent oldest to youngest, of intermediate to felsic dikes, sills, and plugs, felsic (quartz-feldspar porphyry) dikes, sills, and plugs, quartz-porphyry dikes, sills, and plugs, mafic (possibly lamprophyre) dikes, and tertiary andesite (possibly intermediate) dikes. Structurally, the Devonian volcanic-sedimentary sequence forms a large monocline structure gently dipping to the north. Faulting is described in two generalized zones, the Harper Creek fault and the Eastern Domain Structures. The Harper Creek fault is a large fault zone that trends northeast and appears to dip approximately 70 to 75 degrees to the southeast. The zone contains multiple gougy faults, and quartz and iron carbonate fault breccias. The eastern domain structures cause offsets in the mineralized zones and trend southwest with a northwesterly dip of 20 to 35 degrees (Collins, J., et al. (2012-03-29): Technical Report and Feasibility Study for the Harper Creek Copper Project).

Copper mineralization is confined to tabular-shaped zones within light silvery grey quartz-sericite phyllites, with lesser amounts of green chloritic phyllite, dark grey carbonaceous phyllite and light grey sericitic quartzite. These rocks locally include thin horizons of quartz-feldspathic orthogneiss.

Chalcopyrite occurs as disseminations and patches along foliations, in steeply dipping, northerly striking fractures, within quartz and quartz-carbonate veins and with massive pyrite-pyrrhotite. Sphalerite, galena, arsenopyrite, molybdenite, tetrahedrite- tennanite, bornite and cubanite are present in minor quantities. Magnetite occurs locally as massive lenses containing minor chalcopyrite.

Sphene occurs evenly disseminated or in clusters within chloritic phyllite. Rocks with 15 to 20 per cent sphene contain an average of 2.0 per cent titanium (Property File - Belik, 1973).

The tabular mineralized zones strike approximately east and dip about 25 degrees to the north, in approximate conformity with the schistosity and lithology of the host rocks. In detail, however, the zones transgress lithologic contacts and are not stratigraphically controlled. The main mineralized zone is about 1800 metres long, has a local thickness of 100 metres and has been explored downdip for 600 metres. A north-northeast trending, southeast dipping fault cuts the zone midway.

The East zone contains indicated open pittable reserves of 53 million tonnes grading 0.37 per cent copper and 0.016 per cent molydenum. Bench-scale tests indicate 2.8 grams per tonne gold and 88.4 grams per tonne silver. There are also significant titanium values (Application for Listing 14/87, Aurun Mines Ltd.).

In 1966, stream sediment sampling and prospecting by Noranda Exploration Company and Quebec Cartier Mining Company independently discovered the occurrence.

In 1967 to 1971, Noranda and Québec Cartier independently conducted geophysical surveys including ground magnetometers, very low frequency electromagnetic and IP surveys. Trenching was completed in 1967 by Québec Cartier although no results were reported. Drill programs were conducted by Noranda in 1968 although no results were given.

In 1972, soil sampling by Québec Cartier focused on copper found buried mineralized bodies named K and M zones that led to successful trenching on the K Zone.

In 1996, American Comstock conducted a 2,847.4 metre drill program between eight holes on the K-Zone and Area 1. Although results were not explicitly given, it was stated the drill program successfully extended the area of known mineralization (Narcisco, N., et al (2011-03-31): Technical Report and Preliminary Assessment of the Harper Creek Project).

By 1997, American Comstock Exploration Ltd. had aquired a 100 per cent interest in the project and had conducted a 9-hole diamond drilling program (in 1996). A 171-metre intersection assayed 0.31 per cent copper (Exploration in BC 1996, page D5). The program was designed to increase a previously calculated geological resource of 96 million tonnes grading 0.41 per cent copper, 0.045 gram per tonne gold and 2.5 grams per tonne silver (Information Circular 1997-1, page 29).

Yellowhead Mining acquired the Harper Creek project in 2005.

From 2005 to 2009, Yellowhead Mining Inc. conducted a series of six exploration programs on the property containing the occurrence. The work included drilling programs, soil sampling, rock sampling, magnetometer surveys, aerial photography surveys, petrographic studies, and an induced polarization survey. Diamond drilling on the Harper Creek Properties totals 27,636 metres between 75 holes (Narcisco, N., et al (2011-03-31): Technical Report and Preliminary Assessment of the Harper Creek Project). The 2006 drilling program intersected multiple mineralized zones of volcanogenic hosted sulphides, characteristic of deposits. In 2007, a Yellowhead Mining Inc. conducted a 15,904 metre drilling program across 40 holes and intersected multiple mineralized horizons, although grades were not given.

In March 2011 Yellowhead Mining released a Preliminary Economic Assessment Report which included updated resource amounts as follows: (Stockwatch News Release March 8, 2011)

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Category         Amount (tonnes)        Cu(%)     Au(g/t)    Ag(g/t)
Measured          89,992,900            0.30      0.033      1.18
Indicated        442,071,100            0.31      0.032      1.06
Inferred         117,236,900            0.29      0.032      1.32
Calculated at 0.20 per cent Cu cut-off
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In December 2011, drilling at Harper Creek totalled 318 holes for 78 164 metres, not including eight geomechanical holes. Yellowhead Mining Inc. then conducted a mineral resource estimate concluding at a cut-off grade of 0.2 percent copper 348,515,000 tonnes was measured at 0.31 percent copper, 0.034 grams per tonne gold, 1.3 grams per tonne silver, 466,482,000 tonnes were indicated at 0.28 percent copper, 0.030 grams per tonne gold, and 1.3 grams per tonne silver, and 80,169,000 tonnes inferred at 0.30 percent copper, 0.033 grams per tonne gold, and 1.4 grams per tonne silver (Collins, J., et al. (2012-03-29): Technical Report and Feasibility Study for the Harper Creek Copper Project).

In 2011, drilling programs and relogging of historic core by Yellowhead Mining Inc found mineralized zones of significance. Highlighted results included 0.41 percent copper over 31.81 metres at 183.75 metres depth in section 303820E, 0.48 percent copper over 33.52 metres at 9.14 metres depth in section 304180E, and 0.50 percent copper over 45.47 metres at 13.72 metres depth in section 304300E (Collins, J., et al. (2012-03-29): Technical Report and Feasibility Study for the Harper Creek Copper Project).

In December 2012, Yellowhead Mining started an 11,000-metre infill drilling program aimed at upgrading the category of resources within the pit area and allowing for more detailed mine planning and potential exploration benefits.

Yellowhead Mining's 2012 announcement of its updated resource estimate showed that its program of infill and step-out drilling expanded the resource by 47 per cent. The measured and indicated resource at a 0.2 per cent copper cut-off grade stands at 814 997 000 tonnes at 0.29 per cent copper, 0.032 gram per tonne gold and 1.3 grams per tonne silver. A further 80 169 000 tonnes at 0.3 per cent copper, 0.033 gram per tonne gold and 1.4 grams per tonne silver are estimated in the inferred resource category. (www.yellowheadmining.com).

From 2010-2013, Yellowhead Mining Inc. conducted a series of drilling programs at the deposit and along strike and down dip to expand estimates of the mineralized zone. From 2006 to 2013 a total of 58,611.94 metres was drilled across 165 holes (Collins, J., et al (2014-07-31): Technical Report and Feasibility Study of the Harper Creek Copper Project).

In 2014, an updated mineral resource estimate by Yellowhead Mining Inc. concluded at a cut-off of 0.15 percent copper, 564,361,000 tonnes of material measured grading 0.27 percent copper, 0.029 grams per tonne gold, and 1.2 grams per tonne silver, 735,877,000 tonnes indicated grading 0.24 percent copper, 0.027 grams per tonne gold, and 1.2 grams per tonne silver, and 119,743,000 tonnes inferred grading 0.25 percent copper, 0.025 grams per tonne gold, and 1.2 grams per tonne silver (Collins, J., et al (2014-07-31): Technical Report and Feasibility Study of the Harper Creek Copper Project).

In December 2019, a measured and indicated resource of 1 292 000 000 tonnes grading 0.25 per cent copper, 0.028 gram per tonne gold and 1.2 grams per tonne silver with an additional 109 000 000 tonnes inferred grading 0.21 per cent copper, 0.024 gram per tonne gold and 1.2 grams per tonne silver was reported using a 0.15 per cent copper cut-off grade (Weymark, R. [2020-01-16]: Technical Report on the Mineral Reserve Update at the Yellowhead Copper Project, British Columbia, Canada).

In January 2020, Taseko Mines Ltd. released an updated design and feasibility study on the Yellowhead Copper (Harper Creek) project, which includes a larger openpit mined at a higher cut-off grade, resulting in an increase in proven and probable reserves to 817 000 000 tonnes averaging 0.28 per cent copper, 0.030 gram per tonne gold and 1.3 grams per tonne silver using a 0.17 per cent copper cut-off grade (Weymark, R. [2020-01-16]:Technical Report on the Mineral Reserve Update at the Yellowhead Copper Project, British Columbia, Canada).