Geology of Uranium Deposits

Uranium deposits world-wide can be grouped into 14 major categories of deposit types based on the geological setting of the deposits (OECD/NEA & IAEA, 2000). Australian uranium deposits can be grouped into 6 of these categories, with some mineralisation in two further ones:

Unconformity-related deposits - Unconformity-related deposits arise from geological changes occurring close to major unconformities. Below the unconformity, the metasedimentary rocks which host the mineralisation are usually faulted and brecciate. The overlying younger Proterozoic sandstones are usually undeformed.

Unconformity-related deposits constitute approximately 33% of the World Outside Centrally Planned Economies Area (WOCA)'s uranium resources and they include some of the largest and richest deposits. Minerals are uraninite and pitchblende. The main deposits occur in Canada (the Athabasca Basin, Saskatchewan and Thelon Basin, Northwest Territories); and Australia (the Alligator Rivers region in the Pine Creek Geosyncline, NT and Rudall River area, WA).

Unconformity-related deposits constitute a major proportion (20%) of Australia's total uranium resources, and much of Australia's total production since 1980 has been mined from two of these deposits - Nabarlek (now mined out) and Ranger 1 & 3.