Wulser and 3 co-authors reported in early 2013 that the sandstone-hosted Beverley uranium deposit is located in terrestrial sediments in the Lake Frome basin in the North Flinders Ranges, South Australia. The deposit is 13 km from the U-rich Mesoproterozoic basement of the Mount Painter inlier, which is being uplifted 100 to 200 m above the basin by neotectonic activity that probably initiated in the early Pliocene.
The mineralization was deposited mainly in organic matter-poor Miocene lacustrine sands and partly in the underlying reductive strata comprising organic matter-rich clays and silts. The bulk of the mineralization consists of coffinite and/or uraninite nodules, growing around Co-rich pyrite with an S isotope composition (δ34S = 1.0 ± 0.3‰), suggestive of an early diagenetic lacustrine origin.
In contrast, authigenic sulfides in the bulk of the sediments have a negative S isotope signature (δ34S ranges from −26.2 to −35.5‰), indicative of an origin via bacterially mediated sulfate reduction. Minor amounts of Zn-bearing native copper and native lead also support the presence of specific, reducing microenvironments in the ore zone. Small amounts of carnotite are associated with the coffinite ore and also occur beneath a paleosoil horizon overlying the uranium deposit.
Provenance studies suggest that the host Miocene sediments were derived from the reworking of Early Cretaceous glacial or glacio-lacustrine sediments ultimately derived from Paleozoic terranes in eastern Australia. In contrast, the overlying Pliocene strata were in part derived from the Mesoproterozoic basement inlier. Mass balance and geochemical data confirm that granites of the Mount Painter domain were the ultimate source of U and REE at Beverley. U-Pb dating of coffinite and carnotite suggest that the U mineralization is Pliocene (6.7−3.4 Ma).
The suitability of the Beverley deposit for efficient mining via in situ leaching, and hence its economic value, are determined by the nature of the hosting sand unit, which provides the permeability and low reactivity required for high fluid flow and low chemical consumption. These favorable sedimentologic and geometrical features result from a complex conjunction of factors, including deposition in lacustrine shore environment, reworking of angular sands of glacial origin, deep Pliocene weathering, and proximity to an active fault exposing extremely U-rich rocks.
The authors concluded that the sandstone-hosted Beverley uranium deposit can be classified in the tabular type according to the Bruneton and Cuney (2010) synthesis. The mineralization is primarily controlled by sedimentologic features which define the flat-shaped mineralized bodies. The deposit is however quite different from the Colorado Plateau-type mineralization (absence of vanadium, more proximal setting), and more similar to the Arlit district deposits in Niger (similar ore grade, Precambrian basement proximity), although some differences occur (lacustrine origin of the Beverley Sands, age of the mineralization).
It is also interesting to note that the economic value of uranium deposits in the province can be decided by sedimentologic features. Beverley is well suited for cost-effective in situ acid-leaching in situ techniques mining because of its favorable hydrogeologic situation and because the host sediments have the right
porosity [i.e. hydraulic conductivity] and mineralogy (e.g., low carbonate and clay contents). At Beverley, these favorable sedimentologic features
result from a very complex history, including lacustrine shores, high porosity [i.e. hydraulic conductivity], angular sands of ultimately glacial origin, and proximity to an active fault exposing basement rocks exceptionally rich in uranium.
[Additional information on the Beverley uranium deposits]
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