Uranium mineral systems: processes, exploration criteria, and a new deposit framework

Australia holds the world's largest resources of uranium recoverable at low cost, principally in the uranium-rich Olympic Dam iron oxide Cu-Au (IOCG) deposit together with the Ranger and Jabiluka unconformity-related deposits and Yeelirrie surface-related deposit. Despite this impressive inventory, resources of several other styles of uranium deposits appear to be under-represented in Australia relative to geologically similar regions elsewhere in the world. In particular, Australia has no known giant uranium deposits hosted by Mesozoic or younger sedimentary basins, although recent discoveries in the Frome Embayment have significantly increased total resources of `sandstone' uranium in the region. Major deposits directly related to magmatic processes also appear to be under-represented, given the abundance of unusually uranium-rich igneous rocks in Australia. The Australian Government's Onshore Energy Security Program (OESP 2006-2011) is providing pre-competitive geoscientific data and new area selection concepts to assist in reducing exploration risk and to support an assessment of onshore energy and uranium potential.
This report examines the key processes controlling where and how uranium mineralisation occurs in Australia and elsewhere. Based on this process understanding and on descriptions of well-documented systems, we develop generalised models of three distinct families of uranium mineral systems, including exploration criteria. The purpose of the report is to present a revised framework for a fresh assessment of Australia's uranium mineral potential. This systems-based approach, when combined with empirical data, provides a means of identifying previously unrecognised uranium provinces or districts.
The report has three parts. First, the fundamental chemical controls on uranium transport and deposition in aqueous geological systems are reviewed. Second, a new scheme of classification of uranium deposits is proposed (see below). Third, each of three families of uranium mineral systems, plus hybrid systems, is described in terms of ore-forming processes, essential components of the mineral system, and mappable criteria. Exploration models for key systems are presented in figures and tables.