This report contains the results of a seismic survey on the Nerrima Dome, a major structure within the Fitzroy Basin and near its south-western boundary. The dome is situated near the Fitzroy River about 100 miles south-east of Derby in the West Kimberley district of Western Australia. The Nerrima Dome has been mapped at the surface in Permian sediments and is a complex structure. It was desired to determine if the dome existed at depth and, if not, the structure at depth, with a view to locating a site for a deep drilling test. The target beds for such a test are Devonian and/or Ordovician sediments over which the Permian sediments are believed to lie unconformably. Reflection methods were tried and proved unsuccessful and the survey was carried out using refraction methods. Although the structure underlying the dome has not been clearly shown, the refraction method has indicated that it is complex and does not conform with the domal structure at the surface. There appears to be a major unconformity at comparatively shallow depth (2000 ft). The deep structure (7000 ft) although apparently less complex than that immediately below the unconformity, also bears no obvious relation to structure at surface. The results so far obtained are reasonably conclusive in showing that no simple dome-like structure of large magnitude exists under the Nerrima Dome.

This report deals with the results of 25,000 ft. of boring over an area of 15 sq. miles. Twenty-six coal seams were identified and named. Total reserves of all seams with band-free thickness greater than 4.0 ft. are 200,000,000 tons. Net open-cut reserves (to 9:1 ratio) of 7,500,000 tons over an area of 400 acres were tested and defined on four seams. All work in the Howick Area was done in the period March, 1952, to June, 1953.

The area described in the report lies between latitudes 12°48' and 12°56' S., and longitudes 130°56' and 131°11'E. Most of the mapped region lies between the Stuart Highway and the North Australian Railway. The investigation of this area is still in the early stages and has consisted of general geological mapping, and detailed investigation (including drilling) of areas found to have been radioactive during airborne scintillometer surveys carried out in 1952. At Brodribb and Ella Creek superficial hematite-rich deposits have been found to be radioactive to the extent of up to ten times background, but drilling of this type of deposit at Brodribb has not yet proved the existence of payable primary ore. Further drilling is proceeding. A new discovery at Ella Creek in July this year gave high radioactivity over a length of about 300 ft. and two pits sunk to a depth of 3 ft. of this line have shown counts of 5,000 per minute and 10,000 per minute respectively. The field geologists recommend further testing here. In the Frazer area, laterite, which contains a belt of radioactivity up to eight times background, is known to exist, but, apart from limited trenching, has not yet been adequately tested.

Legacy product - no abstract available

The object of this tour was to study ore deposits and methods of exploration in Africa and North America as well as to attend, as Official Delegate of the Commonwealth of Australia, the 19th International Geological Congress held at Algiers in September, 1952. A considerable amount of information was gained concerning ore deposits in the countries visited and this information should be of assistance in the search for further metal deposits in Australia. At the international Congress useful work was achieved and contact was made with a large number of geologists in various parts of the world. These contacts will facilitate the exchange of information between Australia and foreign geologists. The itinerary followed the attached as an Appendix to this report.

Part of 4th March, as well as 5th March, were spent at Carcoar, New South Wales, in inspecting the radioactive deposits in that locality and in observing the use of a helicopter, loaned by the R.A.A.F., as a means of prospecting for radioactive minerals. The writer was accompanied by R.S. Matheson of the Geological Section of the Bureau, and J. Daly and a party of geophysicists were also present at Carcoar at the time of this inspection. The present note is supplementary to the report by R.S. Matheson (1952/65) which includes plans of the Carcoar area and the radioactive deposits, and should be read in conjunction with that report.

The area investigated, of approximately 16 square miles, is 10 miles east of Singleton in the Parishes of Sedgefield and Marwood, County of Durham and in the Parish of Belford, County of Northumberland. The Bureau on Mineral Resources drilled 5 rotary cored bores, as shown on BMR Map N14/109, to 150 ft., 301 ft., 167 ft. 1 in., 202 ft. 8 in. and 131 ft. respectively. The result of drilling was total absence of coal. This may be seen in the attached logs.

An area of approximately 32 square miles in the vicinity of Rye Park has been mapped in greater detail than that of previous regional surveys. Three possible tungsten-bearing areas have been delineated as warranting magnetometric and plane-table surveys. An extension of each of these three areas is indicated. Attention is drawn to copper, tin, silver, lead, and zinc mineralisation of the area, and it is considered that there are possibilities of finding payable orebodies containing these metals.

As a result of a suggestion that electric logging might be employed successfully in coal exploration, a Geophysicist from Melbourne visited Field Headquarters, Muswellbrook and ran electric logs in holes which are being drilled in this district. The equipment consisted of a Widco Logger with one movable electrode capable of measuring Resistivity to a depth of 500 feet. An adaption has been made to this equipment to enable Self Potential to be measured. The details of work done are listed in Table 1 and the results of the logging as compared with the usual method of core-logging are summarized briefly hereunder.

During 1951 three separate sets of La Cour pattern Quartz Horizontal Magnetometers were received from the Danish Meteorological Institute. These instruments which are only semi-absolute, were calibrated at the Rude Skov Magnetic Observatory against the standard adopted by that observatory. As the Australian observatories are based on the International Magnetic Standard housed at Cheltenham near Washington, U.S.A. (hereinafter referred to as I.M.S.) it was decided to compare them against the Toolangi magnetometer as soon as possible after their arrival in Australia. Moreover, as the stability of these instruments depends on the torsion properties of a quartz fibre and on the magnetic moment of a magnet, regular comparisons should be made with an absolute magnetometer and the results used to control drift that might occur. The comparisons made immediately after the arrival of the instruments in Australia would thus constitute a starting point in the future control of the Q.H.Ms. [An account is given of work done between 1951 and 1952. Results are appended.]