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Koocanusa: Purcell Basin Copper Beds

Overview First Nations Engagement Purcell Basin Copper Beds Copper-Bearing Lithologies Koocanusa Data Centre

Basin Model

Formation of Copper Beds in the Purcell Basin

The images below walk you through a simplified model of how the Purcell Basin formed and then subsequently became infilled with sediments and igneous rocks through half a billion years of geological processes. Use the arrows to navigate through.

Stage 01

1.5 Billion Years Ago (Aldridge Formation)

As the ancient supercontinent of Nuna breaks apart, a rift forms and splits ancestral North America from what will become Siberia and Australia. The rift forms a depression that becomes the Purcell Basin, infilled with a deep sea. The sediments interact with volcanism from the rifting and form deposits such as the Sullivan Mine hosted in the Aldridge Formation.

Stage 04

1.4 Billion Years Ago (Sheppard Formation)

As the volcanism ceases, the crust deflates, and the waters return to the basin forming a broad but very shallow sea. These form ideal conditions for reefs made of mounds of cyanobacteria called “stromatolites” which we find fossilized across the project site. Unlike the older layers of sand and silt, the Sheppard Formation is dominated by carbonates and dolomitic rocks.

Stage 05

840 Million Years Ago

Over half a billion years pass and more sediments build up in the basin creating immense pressures. The brines trapped between grains start to circulate as they are squeezed, and their caustic nature dissolves metals from the rocks and transports them to focused traps. Some access the polymetallic Aldridge Formation, while others can only scavenge the basalts, forming the “West” and “East” divisions we see today.

Purcell Basin formation, stage 1 of 6: 1.5 Billion Years Ago (Aldridge Formation)

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Koocanusa: Purcell Basin Copper Beds

Formation of Copper Beds in the Purcell Basin

1.5 Billion Years Ago (Aldridge Formation)

1.45 Billion Years Ago (Creston-Revett)

1.42 Billion Years Ago (Nicol Creek Formation)

1.4 Billion Years Ago (Sheppard Formation)

840 Million Years Ago

Copper Formation Today

Koocanusa: Purcell Basin Copper Beds

Formation of Copper Beds in the Purcell Basin

1.5 Billion Years Ago (Aldridge Formation)

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