The Milligan West occurrence is located approximately 9 kilometres south of Mt. Milligan’s summit, 74 kilometres north-northeast of the community of Fort St. James and 160 kilometres northwest of Prince George.

The Milligan West occurrence lies on the Upper Triassic to Lower Jurassic Quesnel terrane. It is underlain by the Quesnel trough, which comprises a belt of Lower Mesozoic volcanic rocks and intrusions. The Quesnel trough hosts many alkalic and calc-alkalic porphyry copper-gold deposits within British Columbia.

Outcrops exposed along the northeast-flowing tributary of Wittsichica Creek are composed of feldspar porphyries and iron-stained Takla Group fragmental volcanics. Dominant volcanics are andesite heterolithic breccias, and intrusives range from gabbro through diorite to quartz monzonite. Most rocks were found to be hydrothermally altered. The dominant alteration is a propylitic assemblage of moderate intensity; however, significant numbers of boulders showed phyllic/sericitic and lesser potassic alteration. The dominant faulting directions were interpreted to be northwest-southeast and northeast-southwest with a lesser east-west component (Assessment Report 37216).

Exploration for porphyry copper and copper-molybdenum in the Nation Lakes area began in the 1960s and 1970s. The discovery of the Mt. Milligan copper-gold deposit led to a significant amount of base and precious metal exploration in the surrounding area in the late 1980s. In 1989, a 425 line-kilometre airborne magnetometer and very low frequency electromagnetic survey revealed two areas of anomalous magnetic response. In September 1989, the two anomalous areas were further investigated; a 47.7 line-kilometre ground magnetometer survey was performed and located a number of discrete magnetic highs.

In 2010, Fjordland Explorations and Vic Tanaka conducted a prospecting and soil geochemistry program. In total, 28 soil samples were collected at 50-metre intervals. The samples yielded maximum values of 68 parts per million copper (MS 2), 2.5 parts per million molybdenum (MS 1), 0.029 parts per million gold (MS 26) and 0.3 parts per million silver (MS 12; Assessment Report 32095).

In 2011, Hendex Explorations Limited collected a total of 99 soil samples for their soil sample program. Several weak gold-copper-molybdenum anomalies were identified; the highest yields were 67 parts per million copper (L24N 2300E), 0.322 parts per million gold (L12N 1400E) and 13.4 part per million molybdenum (L12N 1200E; Assessment Report 32703).

Serengeti Resources and Fjordland Exploration Incorporated conducted a diamond drilling program in 2017. Three NQ drillholes, totalling 1250 metres, were completed by Radius Drilling. Of the three drillholes, cores MW-17-02 and MW-17-01, located 600 metres south, intersected skarn and feldspar porphyry dykes. Drillhole MW-17-02 yielded 1.57 grams per tonne of gold over 1.5 metres and MW-17-01 yielded 33.5 grams per tonne of silver over 3.1 metres (Assessment Report 37216).

In 2018, a soil and stream sample program was completed approximately 500 metres north of the Milligan West occurrence. In total, 15 Ah soil and 1 stream sediment sample were collected at 100-metre intervals; no significant results were found.