Ten km west of Centerra Gold’s Mt. Milligan Mine and ten km south of Chuchi copper-gold deposit

Located in central British Columbia


Onjo is located 70 kilometres north of Fort St James and 10 kilometres west of Centerra’s Mount Milligan mine (Figure 1), within the Quesnellia arc, host to several significant alkalic copper-gold porphyry deposits such as the Chuchi copper-gold deposit and the Kwanika deposit.


On June 3rd, 2021 Orogen announced the acquisition of the Onjo copper-gold porphyry property. The Onjo property was identified through Orogen’s generative exploration programs and recently acquired through staking.

Property Highlights

·       Onjo is located in the Quesnellia arc and on a magnetic trend hosting the Mount Milligan mine (proven and probable reserves of 959 million pounds copper and 2.4 million ounces gold (1)), and the Kwanika and Chuchi copper-gold deposits

·       Historical drilling intersected multiple small dykes of monzonite associated with anomalous copper mineralization

·       Relogging of historical drilling by Orogen highlights an approximate 500 by 500 metre zone with indicators of the top of an alkalic porphyry copper-gold system

Orogen’s technical team believe vectoring into copper-gold mineralization from the tops of alkalic porphyry copper-gold systems represents a significant exploration opportunity in British Columbia as all major discoveries to date are eroded to the level of the mineralizing intrusion (2). 

Major porphyry copper-gold systems including Newcrest’s Cadia-Ridgeway mines in New South Wales, Australia and Vale S.A.’s Onto copper-gold deposit in Indonesia, which were discovered where mineralizing intrusions occur at depth, provide excellent analogues to generate porphyry targets such as the Onjo property.


Figure 1: Onjo Property located in central British Columbia

About the Onjo Property

The 97 square-kilometre Onjo property is located 70 kilometres north of Fort St James and 10 kilometres west of Centerra’s Mount Milligan mine (Figure 1) within the Quesnellia arc, host to several significant alkalic copper-gold porphyry deposits. The Onjo property occurs on the same magnetic trend that hosts the Mount Milligan mine, the Chuchi deposit and Northwest Copper Corp.’s Kwanika deposit (Figure 2).

The Onjo claims are predominantly underlain by the Witch Lake Diorite which intruded andesitic volcaniclastics of the Quesnel terrane. The geology and geochemistry of the property is largely covered by glaciofluvial and lacustrine sediments with rare outcrops of an extensive copper-gold skarn, a focus of shallow diamond drilling in the early 1990’s. Historic drilling also identified multiple occurrences of thin monzonite dykes associated with minor potassic alteration and copper anomalism, an analogous host rock to the Mount Milligan mine mineralization. 

Relogging of the historic drill core by Orogen identified multiple indicators of the top of an alkalic porphyry system including garnet skarns, copper-gold skarns, late barren lithocap, magnetite and hematite replacement of pyroxenes and copper bearing leakage structures. These features are highlighted over a 500 by 500 metre region prospective for a buried alkalic porphyry copper-gold system.

Additional exploration plans include airborne geophysical survey across the principal target area to delineate prospective monzonite plugs within the larger diorite body for drill target generation.

Onjo copper-gold project British Columbia Orogen Royalties
Figure 2: Magnetic Trend in the Quesnellia Arc (3)

1.   https://www.centerragold.com/operations/mount-milligan/history

2. https://www.youtube.com/watch?v=NPefg5Ruk6w&t=3297s

3.     http://www.geosciencebc.com/major-projects/quest/

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