Minerals Alert August 2008

  1. New Gravity Anomaly Grid of the Australian Region
  2. Update on geophysical data releases
  3. National Geochemical Survey of Australia update
  4. Useful Geoscience Australia websites
  5. About Minerals Alert

1. New Gravity Anomaly Grid of the Australian Region

Geoscience Australia has recently released new gravity anomaly grids of the Australian Region. The gravity grid was produced from 1.4 million onshore gravity stations and 10.5 million offshore gravity stations derived from satellite altimetry. The gravity grid incorporates improvements made to the data in the Australian National Gravity Database (ANGD). In 2008 data in the ANGD were changed to the new Absolute Gravity Datum 2007 (AAGD07) superseding the previous ISOGAL84 datum. This new gravity datum was the end result of several years work by Geoscience Australia in creating an absolute datum for the Fundamental Gravity Base Station Network. Other improvements to the ANGD involved the use of ellipsoid heights relative to the GRS80 ellipsoid instead of geoid ground heights, the closed form of the theoretical gravity formula, the closed form equation for the Bouguer correction and a second order approximation for the Free Air correction. These improvements were made to provide more accurate Free Air and Bouguer anomalies and to remove long wavelength errors from the gravity data introduced when using geoid heights in place of ellipsoid heights.

Two grids have been produced. One grid covers the region from 8° S to 52° S and 100° E to 170° E. Data for the offshore region were sourced from the Marine Gravity from Satellite Altimetry dataset available from Scripps Institution of Oceanography, California, United States of America. This grid is a combination of Bouguer gravity anomaly values for the onshore stations and free air gravity anomaly values for the offshore region. The other grid of Bouguer gravity anomaly values covers Continental Australia only. Both grids have a cell size of 0.008333333 degrees (approximately 800 metres).

The new grids can be obtained free of charge using the Geophysical Archive Data Delivery System GADDS.

For further information, email Mario Bacchin; or phone within Australia: 02 6249 9308, International: +61 2 6249 9308.

2. Update on geophysical data releases

View the current status of Geoscience Australia's geophysical survey data acquisition.

Data will be available via GADDS on 7 August 2008 on The West Musgrave gravity survey.

For further information, email Murray Richardson or phone within Australia: 02 6249 9229, International: +61 2 6249 9229.

3. National Geochemical Survey of Australia update

The National Geochemical Survey of Australia (NGSA) aims to produce the first geochemical atlas of Australia based on the multi-element analysis of transported regolith samples collected at the outlet of around 1400 large catchments covering 91% of the continent. The project, which is a collaborative venture with the geological surveys of all States and the Northern Territory under the National Geoscience Agreement umbrella, started in January 2007. Recent progress includes:

  • sample collection nationally has reached 65%
  • sampling is completed in Tasmania, Victoria and New South Wales
  • 25% of the total samples will be submitted for analysis before the end of September 2008
  • the project will be the subject of an invited keynote address at the 33rd International Geological Congress held in Oslo later this month.

View background information on the NGSA project and an updated map of sampling progress as at 30 June 2008.

For further information, email Patrice de Caritat; or phone within Australia: 02 6249 9378, International: +61 2 6249 9378.

4. Useful Geoscience Australia websites

Geoscience Australia's website provides easy access to a comprehensive range of satellite data of interest to mineral explorers.

5. About Minerals Alert

For more information contact Mike Huleatt on +61 2 6249 9087 or email mike.huleatt@ga.gov.au.

To view past editions of Geoscience Australia's Minerals Alert, visit the Minerals Alert Newsletter Archive.

Topic contact: media@ga.gov.au Last updated: October 4, 2013