A geophysical test survey was made at the Mt. Brown Copper Mine, Karangi, N.S.W in October, 1954. The survey was undertaken by the Bureau of Mineral Resources at the request of the Mt. Brown Copper Mining Company, supported by the New South Wales Department of Mines, to assist in prospecting the leases for additional ore reserves. Reopening and developing the present workings is uneconomical without further prospects. Self-potential, electromagnetic and radioactive methods were used in the survey. The magnetic results show a distinct pattern, but this appears to be unrelated to the known deposit and cannot be interpreted satisfactorily until a regional geological survey of the area has been made. It is recommended that this be done. No self-potential anomalies or electromagnetic indications which could be caused by an ore body, were obtained in the surveyed area. Parts of the area were unsuitable for electromagnetic work because of the effects of electric power lines. The very weak variations observed in the self-potential values are accounted for by small local surface effects. .Random radioactive readings over the area gave no indications of radioactivity above background level.

On the recommendation contained in a preliminary report issued by the Bureau of Mineral Resources in 1952, a magnetic survey was made of several deposits of magnetite in the parishes of Puggoon and Tallawang, near Gulgong, N.S.W. The magnetic results are compared with test results from the quarry at the nearby Tallawang deposit and it is shown that the small deposits studied are not likely to be of sufficient interest to the present lease-holders. Attention is directed to the Tallawang deposit where it is possible that further development of the known ore-bodies, will expose additional reserves of magnetite. A detailed magnetic survey of the area is recommended.

Self-potential and magnetic surveys made in the vicinity of the Mount Cleveland Tin Mine, near Waratah, Tasmania, are described and discussed. The first survey, which is described in Part I of this report, was made in April and May, 1953, at the request of the Department of Mines, Tasmania. The object of the survey was to ascertain whether geophysical methods could detect the known area of mineralisation and, if so, whether any additional areas of mineralisation could be discovered. Results of the first survey show that the geophysical anomalies, particularly the self-potential ones, coincide with the old mine workings. The anomalies over Luck's and Hall's workings, however, cover larger areas than the actual mine workings, thus indicating that further sulphide mineralisation may exist beyond these old workings. Anomalies not related to the old workings appear in an area north-west of Deep Creek, between traverses O and R. Both self-potential and magnetic methods revealed anomalies along these traverses between 350.E and 650.E, where geological investigation has also shown mineralisation to exist. Based on the results of the first survey, the grid was extended and surveyed to the north-east and south-west in March and April, 1954. This second survey, which is described in Part 2 of the report, shows that the anomaly connected with Henry's workings does not extend to the north-east, but terminates sharply between traverses P and Q. Some additional anomalies were recorded in the north-eastern extension of the grid, but in the south-western extension there was no geophysical evidence of mineralisation. It is suggested that further mining exploration work should be concentrated mainly near the former mine workings and in the area to the north-west of Deep Creek, between traverses O and R. Some prospecting trenches should also be put down to test the minor anomalies in the north-eastern part of the area.

In response to applications by the Tasmanian Department of Mines and the interested company, Eagle Metal and Industrial Products Pty. Ltd., Tasmania, a geophysical investigation, including self-potential, electromagnetic and magnetic surveys, has been made over the copper-nickel deposits of the North Dundas Field, situated about 5 miles north-east of Zeehan, Tasmania. The nickel ore occurs in the foot-wall of north-striking ultrabasic dykes. The ore shoots already worked had proved very rich but quite small. Important results were obtained in the Cuni North Area only. Conductive indications which appear to be due to mineralization extend over a length of 800 to 1000 feet. The line of mineralization is intersected by cross faults. Drilling targets for five short diamond drillholes are given. Further exploration should be confined mainly to this area. The geophysical results indicate that mineralization farther south is limited in extent and perhaps of no economic interest.

At the request of Australian Magnetite Pty. Ltd. of Melbourne and with the approval of the New South Wales Mines Department a geophysical survey was carried out over a lease held by that Company near Gulgong, New South Wales, in the Parish of Puggoon in the County of Bligh. The area is situated about 7 miles north of Gulgong where the Company operates a mill for crushing, fine grinding and concentrating magnetite ore. The pulverized, concentrated magnetite is used in the heavy liquid separation and cleaning of coal. The present supply of magnetite ore comes from the magnetite mine at Tallawang, about 12 miles from Gulgong. As a results of increasing difficulties in mining this deposit, the best part of which has already been stoped out, Australian Magnetite Pty. Ltd. is desirous of opening up and developing a new and suitable deposit in order to ensure the necessary continuous supply of ore to the mill. The deposit of magnetite in the Parish of Puggoon is partly exposed in outcrops and in a trench, and is probably of lens-like form. It occurs in a Silurian formation. The task set for the geophysical survey was to determine the full extent of the deposit and its approximate shape before a decision was made on a position for a new opencut.

Results are given of a geophysical test survey made at three localities on the Newcastle coalfield in August, 1952, to determine whether intrusive doleritic dykes could be located by the magnetic method. Knowledge of the position of the dykes would assist in planning the lay-out of underground workings and of surface roads. The results showed only slight variations of the magnetic field, but some weak anomalies of less than 100 gammas were recorded. The position of these anomalies coincides with the inferred position of the basic dykes near the surface. The variation in the shape of anomalies suggests non-uniformity of the magnetic properties and shape of the dykes. The magnetic method might be helpful in determining the position and extent of the dykes beyond the areas where they are known, but supporting evidence from other geophysical methods such as the gravity of electric resistivity methods may be needed to verify the magnetic results.

This dataset includes magnetotelluric (MT) sounding data collected in July 2019 in the Silverton Caldera complex, Colorado, in the Southern Rocky Mountain Volcanic Field, by the U.S. Geological Survey (USGS). Along with geologic mapping, airborne magnetics, airborne electromagnetics, and audiomagnetotellurics, the USGS collected MT data at 24 sites along five profiles ranging from 2 to 5 kilometers in length: across Red Mountain of the Silverton caldera, within the caldera in Eureka Graben, across the south-eastern margin of the caldera along Arrastra Gulch, across the southern margin of the caldera along the western margin of Kendall Mountain, and across the south-western margin of the caldera along South Fork Mineral Creek. The data included here are for MT station MTEG06 located in Eureka Graben.

This dataset includes magnetotelluric (MT) sounding data collected in July 2019 in the Silverton Caldera complex, Colorado, in the Southern Rocky Mountain Volcanic Field, by the U.S. Geological Survey (USGS). Along with geologic mapping, airborne magnetics, airborne electromagnetics, and audiomagnetotellurics, the USGS collected MT data at 24 sites along five profiles ranging from 2 to 5 kilometers in length: across Red Mountain of the Silverton caldera, within the caldera in Eureka Graben, across the south-eastern margin of the caldera along Arrastra Gulch, across the southern margin of the caldera along the western margin of Kendall Mountain, and across the south-western margin of the caldera along South Fork Mineral Creek. The data included here are for MT station MTEG06 located in Eureka Graben.

This dataset includes magnetotelluric (MT) sounding data collected in July 2019 in the Silverton Caldera complex, Colorado, in the Southern Rocky Mountain Volcanic Field, by the U.S. Geological Survey (USGS). Along with geologic mapping, airborne magnetics, airborne electromagnetics, and audiomagnetotellurics, the USGS collected MT data at 24 sites along five profiles ranging from 2 to 5 kilometers in length: across Red Mountain of the Silverton caldera, within the caldera in Eureka Graben, across the south-eastern margin of the caldera along Arrastra Gulch, across the southern margin of the caldera along the western margin of Kendall Mountain, and across the south-western margin of the caldera along South Fork Mineral Creek. The data included here are for MT station MTEG07 located in Eureka Graben.

This dataset includes magnetotelluric (MT) sounding data collected in July 2019 in the Silverton Caldera complex, Colorado, in the Southern Rocky Mountain Volcanic Field, by the U.S. Geological Survey (USGS). Along with geologic mapping, airborne magnetics, airborne electromagnetics, and audiomagnetotellurics, the USGS collected MT data at 24 sites along five profiles ranging from 2 to 5 kilometers in length: across Red Mountain of the Silverton caldera, within the caldera in Eureka Graben, across the south-eastern margin of the caldera along Arrastra Gulch, across the southern margin of the caldera along the western margin of Kendall Mountain, and across the south-western margin of the caldera along South Fork Mineral Creek. The data included here are for MT station MTEG07 located in Eureka Graben.