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Geophysical response of heavy-mineral sand deposits at Jerusalem Creek, New South Wales

BMR has started evaluating how geophysical methods might assist in exploration for deposits of the heavy minerals rutile, zircon, ilmenite, and monazite. Historically, exploration for these heavy minerals has concentrated on the search for high-grade onshore beach-sand deposits, and has employed surface sampling and shallow drilling. However there is a growing awareness that future exploration targets are likely to be low grade and perhaps either deeply buried or located offshore. Exploration directed towards these targets will require new exploration methods, particularly those which offer remote sensing capabilities. BMR has begun a program of test surveys and laboratory investigations to establish the geophysical response of heavy-mineral deposits. As the first stage of these investigations, airborne and ground geophysical surveys were made over heavy-mineral deposits in the Jerusalem Creek area of NSW during 1975. Jerusalem Creek was chosen for the initial field investigations because of the variety and extent of heavy-mineral deposits in the area. The airborne survey (Fig. 1) was carried out over an area of 200 sq km of coastal plain south of Evans Head, and used magnetic and gamma spectrometer methods. Ground surveys were conducted over the Evans West and GL 10 deposits, using magnetic, radiometric and induced polarization methods. The locations of the Evans West and GL 10 deposits are shown in Figure 1. The Evans West deposit is 2 km in length, 3 m thick, 30 m wide, and is covered by 3 m of overburden. The deposit has a fairly sharp grade cut-off at its boundaries, and averages about 10 percent heavy minerals comprising 36 percent zircon, 35 percent rutile, 25 percent magnetics, minor monazite and other minerals. The magnetic fraction is largely ilmenite. The GL 10 deposit has a similar mineral composition but the deposit consists of several parallel leads up to 40 m wide. The average grade of the deposit is only 1-5 percent, and the deposit is buried under only 0.5 m of cover. The magnetic, radiometric and induced polarization methods were used because the mineral assemblage of the Jerusalem Creek deposits suggests susceptibility, radioactivity and induced polarization contrasts between ore and the surrounding sands. The Evans West and GL 10 deposits were chosen as ground survey sites because extensive mine development drilling provided excellent geological control for the interpretation of geophysical results. To establish the physical properties of heavy-mineral ores and to assist interpretation of the geophysical surveys, laboratory measurements of susceptibility, induced polarization and radioactivity were made of ore and sand samples collected from the Evans West deposit. The surveys at Jerusalem Creek were carried out in close co-operation with Associated Minerals Consolidated (AMA), whose assistance in the planning and carrying out of the survey is gratefully acknowledged.

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Additional Info

Field Value
Title Geophysical response of heavy-mineral sand deposits at Jerusalem Creek, New South Wales
Type Dataset
Language English
Licence Creative Commons Attribution 4.0 International
Data Status inactive
Update Frequency unknown
Landing Page https://data.gov.au/dataset/d758f883-4233-466c-9fd6-9b4bc5fd358a
Date Published 2017-06-25
Date Updated 2017-06-25
Contact Point
Geoscience Australia
clientservices@ga.gov.au
Geospatial Coverage {"type": "Polygon", "coordinates": [[[153.1, -29.5], [153.6, -29.5], [153.6, -29.0], [153.1, -29.0], [153.1, -29.5]]]}
Jurisdiction Commonwealth of Australia
Data Portal Geoscience Australia CSW Harvester
Publisher/Agency Geoscience Australia
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