Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Beach sand deposits along the Australian east coast (Gardner, 1951 a, b) have yielded a large part of the world supply of zircon and rutile since the year 1936. During 1953 the returns from the export of these minerals amounted to more than £2,000,000. In addition the black sands contain a small proportion of monazite, which is a source of cerium and of thorium, a fissionable element that may be used for the generation of atomic power. From a comparatively small beginning the mid-1930's the beach-sand industry grew rapidly during the war and early post-war years. Little was known of the distribution and reserves of the deposits; hence the Bureau of :Mineral Resources undertook a detailed investigation of the coastal area between Southport, Queensland, and Woody Head a little north of the mouth of the Clarence River, New South Wales. The primary object of the survey was to determine the reserves of monazite and therefore of thorium; the reserves of zircon, rutile, and ilmenite were also determined. In this report the source rocks of the sand and heavy minerals are considered in a brief outline of the physiography and general geology of the country between the coast and the main divide. The deposits are described and their origin and distribution discussed in connexion with late Pleistocene and recent changes, in sea level. The reserves and distribution of the heavy minerals arc broadly summarised, and more details of reserves and dimensions of deposits and overburden are given in descriptions of the individual areas.

In July, 1949, the Bureau of Mineral Resources, Geology and Geophysics began an investigation of the geology and mineral resources of the Harts Range Region, Central Australia, an area of about 2,000 square miles between Latitudes 23° 00' south and 23° 30' south, and Longitudes 12:3° 45' east and 135° 30' east. The undertaking was prompted by the discovery of small amounts of radioactive minerals in pegmatites in the eastern portion of the range. It was soon realized that the deposits of radioactive minerals were not of economic size, and the investigation was therefore extended to other mineral deposits, and in particular to the mica deposits of the Harts Range and Plenty River.he Harts Range and Plenty River Mica Field is the most. Important in Australia, and had yielded 859.49 tons of commercial muscovite .valued at £692,794 to the end of 1952. The investigation of the field was carried out in field seasons between July, 1949, and October, 1951. The mica-bearing pegmatites occur in the rocks of the Harts Range Group, a complex of metamorphosed igneous and sedimentary rocks probably of Archaeozoic age.

The Cape Range Structure, which occupies the North-West Cape peninsula, is a closed anticline in Tertiary limestones. The structure is at least eighty miles long and twenty miles wide, and has a vertical closure of 1200 feet and a closed area of 1200 square miles. The physiography is a reflection of the structure-a young fold mountain with mainly consequent, closely-spaced, drainage. The Tertiary sediments were laid down in a shelf area of the southwestern arm of the Indo-Pacific geosyncline. Because of the stability of the adjoining Western Australian shield, they did not attain the thickness of the sediments laid down elsewhere in the Indonesian geosyncline, nor were they affected to the same extent by subsequent tectonic disturbance. Five Tertiary formations are exposed on the Cape Range-the lower Miocene (e-stage) Mandu Calcarenite (265 feet of chalky limestone), the lower Miocene (f1-stage) Tulki Limestone (225 to 420 feet of hard crystalline limestone) and the possibly lower Miocene (f1 to , ?f2stage). Trealla Limestone (18'0 feet of white crystalline limestone), constituting the Cape Range Group; and the possibly lower Miocene Pilgramunna Formation and possibly Pliocene Vlaming Formation, forming the Yardie Group (calcareous sandstone and fine conglomerate up to 300 feet thick). Beneath the Miocene limestones are probably at least 3,000 feet of Cretaceous and Eocene marine sediments and possibly up to 18,000 feet of Permian, Carboniferous, and Devonian marine sediments. In vertical closure and closed area the Cape Range Structure is' the largest in the Carnarvon (North-West) Basin. Potential drainage of oil is unrestricted on the west flank and on the northern two-thirds of the east flank. Further geophysical (gravity and seismic) investigations should be carried out so as to try to determine the thickness of sediments and the shape of the structure in depth.