Horizontal gravity components measured by the Sander Geophysics’ AIRGrav system in the East Kimberley 2016 aerogravity survey were released on 20 April 2017. The horizontal component datasets and a short supplementary technical report by Sander Geophysics have been added to the survey data package that can be downloaded from the Geo Downloads website.
The horizontal component data complement the vertical gravity data released on 23 February 2017 and can be used to provide an estimate of the variation of the gravity vector and gradient tensor over the survey area. Note that the gravity components are defined using an east–north-up system where the normal gravity of the earth is a vector pointing upwards.
Figure 1 shows images of the three components of the 2500m-spatially filtered ‘gravity anomaly vector’ as measured in Cartesian coordinate space (Gx, Gy, Gz). The values used have been taken from the following located datasets:
|Component||Path in data package||Channel name|
Also shown in Figure 1 are the Cartesian components transformed to spherical coordinates as total magnitude, azimuth from north, and inclination from the vertical, where:
Figure 2 shows images of the six independent components of the anomaly tensor computed as the gradients of the measured Gx, Gy, Gz values in each of the three directions:
Also shown in Figure 2 is an image of the 3D analytical signal,
The derived images in Figures 1 and 2 in georeferenced jp2 format and their source grids in ERMappper format are also included in the updated survey data package under the ‘Derived_grids’ directory.
Figure 1. East Kimberley 2016 aerogravity survey — anomaly vector data
Cartesian coordinates (top); spherical coordinates (bottom); 100 km grid lines
Figure 2. East Kimberley 2016 aerogravity survey — anomaly tensor data
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Report 161 Geochronology of the Rudall Province, Western Australia: implications for the amalgamation of the West and North Australian Cratons
by DW Maidment
U–Pb zircon dating of igneous and metasedimentary rocks from the Rudall Province has revealed aspects of an extended, multiphase history that has implications for models of the assembly of Proterozoic Australia. Detrital zircon dating has identified metasedimentary units of possible Neoarchean to early Paleoproterozoic age, and a possible cover succession deposited after c. 1794 Ma.
The Krackatinny Supersuite in the eastern part of the province yields ages of 1589–1549 Ma and has a range of geochemical compositions consistent with emplacement in a magmatic arc or a rift developed in thickened continental crust. Felsic magmatism and high-grade metamorphism at 1330–1285 Ma reflects a major tectono-thermal event, and possibly dates the Yapungku Orogeny, previously considered to have taken place at c. 1800–1765 Ma. This event has been linked with the amalgamation of the West and North Australian Cratons, and might indicate assembly later than previously thought. Go to DMP eBookshop to download a free PDF copy and accompanying zipped data files.
Report 161 Geochronology from the Rudall Province, Western Australia: implications for the amalgamation of the West and North Australian Cratons
Plus accompanying downloadable zip files
by Maidment, DW
Record 2017/4 Geological reconnaissance of the southern Murraba Basin, Western Australia
by Haines, PW and Allen, HJ
Record 2017/6 TARGET 2017, Perth, Australia: abstracts
edited by Wyche, S and Witt, WK
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