The Northern Territory is an integral part of the great Australian Pre-Cambrian shield which underlies almost the whole of Western Australia and the Northern Territory, much of South Australia and portions of New South Wales and Queensland. In most parts of the Continent, Pre-Cambrian rocks were welded into a stable shield before the end of Pre-Cambrian time, and in the Northern Territory itself the structural framework was established, and most of the mineral deposits introduced by an orogeny which terminated geosynclinal sedimentation about the end of the Lower Proterozoic. This discussion of the structure of the Territory in relation to mineralization is mainly concerned with Pre-Cambrian, and in particular with Lower Proterozoic rocks. Only a broad outline of the subject is given here.

The samples from Margaret Bay were collected by H.B. Owen during a recent visit to the northern coast of Australia. The collection was made with the hope that microfossils may be found in the rocks which were collected from a twenty foot section exposed at Margaret Bay. The results of the micropalaeontological examination are discussed herein.

Ore reserves in the Geiger-Main and Whip Lodes at Radium Hill have been calculated from up-to-date plans and assay data provided by the South Australian Mines Department and results obtained agree closely with estimates made by the Mines Department. Tonnage of ore (not including dilution) to 600 feet depth on Geiger-Main and Whip Lodes and to 400 feet in Main Lode South block is estimated at 337,500 tons containing 938 tons U3O8, corresponding to an approximate average of 160 tons U3O8 per 100 feet of vertical depth. The data used, method of calculation, and results, are discussed at length in this report.

The presence of bauxite on one of the Wessel Islands was established in 1949 when specimens of laterite collected from various parts of the Arnhem Land coast were analysed. In October, 1951, the writer spent two days on Marchinbar Island and examined several small laterite residuals and part of one large deposit. The characteristics and distribution of the laterite are discussed in this report.

Gravity observations were made at quarter-mile intervals along the road that joins Bullara and Giralia homesteads. This road crosses the northern end of the Giralia anticline normal to its axis. A seismic reflection profile, which is described in B.M.R. Record 1951 No. 62, has also been run along this road and it is possible to compare the gravity results with the seismic. Gravity station elevations were determined with an accuracy of within 0.1 of a foot and the gravity observations have been reduced to Bouguer anomalies using an elevation correction factor of 0.062 milligals per foot. The results are shown in the form of a profile on the accompanying plate. The surface profile is also plotted and the positions of some of the seismic shot points are shown alongside the gravity station numbers. These results are discussed in this report.

This report presents the results of a gravity reconnaissance survey which was carried out under the writer's supervision during the last quarter of 1950. The report describes in some detail the methods adopted in carrying out the field work and the errors to which the results are subject. The results are discussed only briefly and the interpretation given must be regarded as a preliminary one subject to modification as further data are accumulated in extending or otherwise adding to the reconnaissance.

This report provides a summary of volcanic activity in the volcanic centres of New Guinea for the year 1951. Extended descriptions are given of ongoing investigations and the volcanological observations made at Rabaul, Mt. Lamington, and other significant volcanoes.

On May 3rd, and again on June 1st, the author visited the Cotter dam to investigate a reported loss of water from the fault on the northern side of the wall. This report gives an account of these visits, together with the author's observations and conclusions in relation to the reported water loss.

Samples from three localities in New South Wales were received for micropalaeontological examination. The results of these examinations are described in this report.

The Treasure Mine, Hatches Creek, is believed to have been discovered in 1914 and has been one of the most consistent producers of wolfram to the present time. This report gives an account of the economic geology of the mine. The ore type, reefs and workings, ore localization, and ore reserves are described.