Palaeozoic sedimentation, tectonics and mineralisation in the Mt. Lyell area (Tasmania) with especial reference to the origin and economic significance of the Lyell schists

The purpose of this thesis is to present the writer's interpretation of the geology of the Queenstown area and to describe the nature and origin of the Lyell Schists, with a view to assisting in any general search for mineralisation on the West Coast of Tasmania and also to assisting in more localised exploration for copper orebodies in mineralised areas. The study has consisted of both regional and detailed field mapping with some laboratory work. Earlier workers in the Queenstown area have disagreed violently on general interpretations and particularly on the Lyell Schists, mainly because the theories have been based entirely on either restricted detailed work or generalised reconaissance work. For the first time, both regional and detailed mapping have been done as units of an overall examination and the two together have thrown new light on the geological picture. As will be shown later, mineralisation and Lyell Schist formation took place during the Devonian Tabberabberan Orogeny; thus the Mesozoic and later geology is of little significance from an economic point of view and will be presented in summary form. The area originally studied is that part of the West Coast Range south of Mt. Sedgwick (see Fig. 1), involving about 300 sq. miles of rugged terrain. This was mapped using aerial photographs of 1 inch = 20 chains scale (or 4 inches = 1 mile) and completion of this work was followed by detailed mapping of the Lyell mine areas in company with the Chief Geologist of the Mt. Lyell Mining and Railway Company. This detailed mapping was done on a scale of 1 inch = 100 ft. and involved an area of a little over 5 sq. miles centred on the West Lyell Open Cut. Further evidence has been brought in from areas further afield that have been mapped by the writer. These are mainly south and west of the West Coast Range, including the Southern Ocean coast, from Cape Sorell to High Rocky Point and the D'Aguilar Range. The general geological picture of this part of the West Coast and the area mapped in more detail is shown in Fig. 2; most of the information relating to the area west of the West Coast Range was supplied by the Hydro-Electric Commission of Tasmania. In conjunction with the field work, over 200 thin sections were made and examined by the writer.