This abstract is to be submitted to the Australian Society of Exploration Geophysicists for consideration as a poster to be delivered at the 22nd ASEG conference and exhibition in February 2012.

During 1999 the Australian Geological Survey Organisation (now Geoscience Australia) operated geomagnetic observatories at Alice Springs and Kakadu in the Northern Territory, Canberra in the Australian Capital Territory, Charters Towers in Queensland, Gnangara and Learmonth in Western Australia, Macquarie Island, Tasmania, in the sub-Antarctic, and Mawson in the Australian Antarctic Territory. This report describes instrumentation and activities, and presents monthly and annual mean magnetic values, plots of hourly mean magnetic values and K indices at the magnetic observatories and repeat stations operated by GA during calendar year 1999.

Legacy product - no abstract available

This report describes the operation of the Mawson geophysical observatory from December 1990 to December 1991. It includes a summary of Mawson geomagnetic data from 1 December 1990 to 12 December 1991. It also describes work carried out in compiling variometer data and absolute observations from Davis and Casey, provided by the Auroral and Space Physics section (ASP) of the Antarctic Division (formerly Upper Atmosphere Physics, UAP) to produce mean monthly averages of the quiet field in the manner of the Mawson reports. Geomagnetic field observations performed in the Prince Charles Mountains (PCMs) and on Heard Island during January and February 1992 are presented in a separate report (de Deuge, 1992).

The report describes instrumentation and activities, and presents data collected at the magnetic observatories operated by Geoscience Australia during the 2013–2016 calendar years.

Our knowledge of the crustal architecture of the Yilgarn Craton has increased greatly over the last decade through the increased collection of a wide range of geophysical and geochemical/isotopic data sets. This range in data varies from: - lithospheric-scale studies using distant earthquakes as sources to obtain information on the entire craton down to depths in excess of 350 km, through; - regional-scale studies providing information at the province scale and down to depths of 30-40km, to; - mine- and camp-scale studies - providing information on the local-scale down to the top few kilometres of the crust. Receiver Function and broad-band teleseismic results map significant variations in crustal and upper mantle velocities across the Yilgarn Craton. The results are also providing information on potential velocity differences between the mineralized Kalgoorlie Terrane and the less mineralized Youanmi Terrane. An anomalous high velocity body (>4.8 km/s shear wave) occurs at around 100-120 km depth, and has steps and edges that correspond with mantle-derived magmas and the main gold camps. The fast velocity layer may represent mantle alteration (mapping a gradient), delaminated eclogite layer, or fossil oceanic slab? Maps of crustal age across the craton have been derived from ~250 analyses of granites of all ages. The Nd model age maps show that the granites were separated from the mantle at a range of ages from 3.6-2.7 Ga. Most ages are significantly older than the crystallisation age (200-300 My) so the crust was extensively recycled. The major changes in crustal age map the different terranes of the Yilgarn Craton and are leading to first order prospectivity for gold, nickel and base metals. Deep crustal seismic reflection studies have provided excellent 2D crustal architecture information in the eastern part of the craton, which in turn, have provided information on the region's mineral systems. These seismic data have imaged the numerous shear zones and are critical in defining the gross 3D architecture (maps) of the crust. Magneto-tellurics map the main boundaries of the Kalgoorlie Terrane. These data reveal that the prospective Kalgoorlie Terrane is special (in MT space), and is characterised by a highly conductive (graphite-bearing?) upper crust (along strike from the Super Pit) and a dome or 'upwelling' of conductive mantle beneath. Together these data provide first-order insights into the physical and chemical properties of the Yilgarn Craton. These insights provide geodynamic clues and constraints on why the Yilgarn is so well endowed.

Legacy product - no abstract available

This report describes the operation of the Mawson geophysical observatory from December 1992 to December 1993. It includes a summary of final Mawson geomagnetic data from 1 January 1993 to 30 December 1993. Monthly averages of the quiet field for Davis and Casey stations have also been produced from data provided by the Auroral and Space Physics section (ASP) of the Antarctic Division.

Legacy product - no abstract available

Legacy product - no abstract available