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The thesis describes in detail the area of the uranium lodes in the South Alligator River valley in the Northern Territory of Australia. The four land forms are described, together with the soils developed on them, and the morphological and genetic relationships of the latter are discussed. The published stratigraphy of the area is recapitulated, and some changes of viewpoint are advocated: an unconformity within the Upper Proterozoic rocks is described; the characteristics of the Scinto Breccia unit are ascribed to silicification of diverse stratigraphic units; the allegedly organic origin of calcareous rocks of the Koolpin Formation is disputed; and the lack of obvious signs of unconformity between the Stag Creek Volcanics (Archaeozoic?) and the Lower Proterozoic sequence is pointed out. A petrological study of a collection of rocks from the area is made, and this includes a description of some diaspore-rich volcanics in which the uranium mineralisation appears to be of syngenetic origin. The characteristics of the ore bodies or radioactive prospects are described, together with the ore-deposition controls. An epigenetic origin is postulated for most of the uranium deposits. Exploration techniques employed in the discovery or evaluation of the ore bodies are discussed, and the results are reported of a programme of geochemical testing of stream waters in the drainage basin. It is concluded that, in this area, the geochemical technique has only limited usefulness for the discovery of uranium. The extraction of ore, and its subsequent treatment by solvent-extraction processes is described. An account is given of some other uranium occurrences in northern Australia viz., the Rum Jungle, Mary Kathleen and Pandanus Creek ore bodies, and the radioactive or mineralised prospects at Denham River and Saunders Creek in Western Australia. A general account of theories of emplacement of uranium ore in Australia and elsewhere postulates an epigenetic origin from a magmatic source for most of the Australian deposits, but accepts a sedimentary origin for the uranium associated with conglomerates. A brief historical survey of developments in the uranium industry pays special attention to events in Australia.
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