Uranium geology in the Athabasca and a comparison with other Canadian Proterozoic basins

CIM Bulletin, Vol. 75, No. 840, 1982

R.J. McH. CLARK, LA. HOMENIUK and R. BONNAR, Eldorado Nuclear Limited, Ottawa, Ontario

The Athabasca Basin has been the scene of an intense exploration effort since the late 1960s, resulting in the establishment of this area as one of the major uranium districts in the world.The Athabasca Group is of Helikian age and unconform-ably overlies metamorphic rocks of Aphebian and Archean age. Most of the known uranium deposits have a close spatial relationship with the unconformity, graphitic meta-sediments, major northeast-trending structures and the basin edge. It should be noted that, in regard to the latter, some of the Cluff Lake deposits are exceptions.The pre-Helikian rocks underlying the Athabasca Group have been divided into six lithostructural domains. The known uranium deposits are concentrated in the Wollaston and Mud-jatik domains in the southeastern portion of the basin.The orebodies typically have a narrow high-grade portion below the unconformity and a broader, lower-grade disseminated zone in the overlying sandstone. Over-all grades average over 1% U3O5 and our estimate of known reserves totals more than 400 million pounds of contained U3O8. Some of the deposits have high concentrations of other metals, including nickel, arsenic, cobalt and gold. Ubiquitous chlorite and clay alteration is characteristic of the orebodies.Other Proterozoic basins in Canada of similar ages and having analogous geological settings to the Athabasca have received far less attention. Although little of the known uranium mineralization in these basins is related to the Helikian unconformity, there may be an exploration potential for deposits similar to those of the Athabasca basin.

Keywords: Mineral exploration, Uranium geology, Athabasca Basin, Proterozoic basins, Rabbit Lake deposit, Cluff Lake deposit, Key Lake deposit, Fond du Lac deposit, Baker area, Thelon area, Hornby Bay area, Dismal Lakes area, Sibley Group, Animikie Group, Sims Formation, Baffin Island, Ramah Group, Labrador Trough, Seal Lake area, Bathurst Inlet, Martin Formation, Sakami Formation, Avalon Zone, Circum-Ungava Geosyncline, Nonacho Group.