RB 2018/00015 Gawler Craton Airborne Geophysical Survey Region 2A, Murloocoppie – Enhanced geophysical imagery and magnetic source depth models. (Data zip file available from SAMRef)
Published: 01 Jun 2018 Created: 15 Nov 2024 Revised: 20 Dec 2024

This report presents the results of a study jointly conducted by the Geological Survey of South Australia and CSIRO Mineral Resources which aimed to enhance the expression of geological structure in geophysical images and to derive depth to...

This report presents the results of a study jointly conducted by the Geological Survey of South Australia and CSIRO Mineral Resources which aimed to enhance the expression of geological structure in geophysical images and to derive depth to magnetic source estimates over Region 2A of the Gawler Craton Airborne Survey; viz. the Murloocoppie area. The study was based on magnetic field data acquired during February-May 2017 by this airborne magnetic and radiometric survey commissioned by the Geological Survey of South Australia, that have been combined with ground gravity data from the South Australian state gravity database. The 2017-18 PACE Copper Gawler Craton Airborne Survey (GCAS) provides both higher resolution and more consistent mapping of the magnetic field than are available from previous coverage by multiple geophysical surveys of lesser extent. Advantages of the new survey data are quite evident upon inspection of the primary total magnetic intensity (TMI) data, but it is through the enhancement of that TMI data to assist in recovery of geological information that the advantages are most clearly expressed. Many of the enhancements presented in this report are necessarily of limited application to the TMI data previously obtained across the Gawler Craton area, mainly because of known numerous insufficiencies and imperfections in those data, and they would be hampered by the unavoidable effects of abrupt signal strength contrast that appear on passing between survey datasets acquired on different line spacings, flying heights or flight-line orientations. The GCAS data acquisition consistency and close line spacing therefore support higher resolution and more confident source depth mapping from the magnetic field data. Local magnetic field variations arise exclusively from ferromagnetic minerals which may only constitute of the order of 2% or less of the rock (even for what are considered strongly magnetised rocks), while lateral variations in geology which have no associated variation in magnetisation have no direct expression in the magnetic field imagery. In contrast, gravity data respond to variations in density, to which all components of the rock contribute. Gravity field variations therefore provide a complementary mapping of geology. Suitable combinations and contrasts of gravity and magnetic fields provide more diagnostic information about the subsurface than does the sum of the two fields processed and imaged independently. The output of this study is a collection of images and digital data products, downloadable herein, which have been generated to facilitate geological interpretation. The products are not themselves interpretive, but provide more direct access to interpretation than do directly measured datasets treated alone. These products, and in particular the magnetic source depth estimates, are designed to provide the genesis of a ‘live’ resource which can be progressively upgraded rather than simply being replaced when further studies are undertaken in the area, the depth solution database is added to, or when new drillhole information is reported.

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About this record

Record No 2018d051203
Topic Geoscientific Information
Type of Resource Document
Category Type
Document Type Exploration Initiative - Collaborative Exploration
Contributor CSIRO Earth Science and Resource Engineering;DPC Resources and Energy Group. Geological Survey of South Australia;Geoscientific Information Strategy Team;South Australia’s 4D Geodynamic and Metallogenic Evolution Team
Sponsor
Tenement
Tenement Holder
Operator
Geological Province
Mine Name
Stratigraphy
Commodity
    Notes
    Notes: Includes, in Appendix 2, the senior author's 322 inversion model magnetic source depth solutions generated from traverses over discrete anomalies discerned in the gridded TMI data.  For the purpose of mapping a possible top-of-basement...

    Notes: Includes, in Appendix 2, the senior author's 322 inversion model magnetic source depth solutions generated from traverses over discrete anomalies discerned in the gridded TMI data. For the purpose of mapping a possible top-of-basement depth surface, the modelled anomaly source depth solutions have been assigned to three populations: - source depths that are considered likely to be generated from magnetisations arising at or near the basement/cover unconformity (233 solutions); - source depths that seem to be too shallow to be due to magnetisations arising from there (27 solutions); and - source depths that seem to be too deep to be due to magnetisations arising from there (62 solutions). The downloadable content to this report includes the following value-add data renditions and products: a) Grids (.ers) and grid images (geotiff) - TMI - RTP of TMI - First vertical derivative of RTP TMI - Second vertical derivative of RTP TMI - TMI total gradient (analytic signal) - RTP TMI with tilt filter - Bzz (vertical gradient of magnetic total field vertical component) - Bouguer gravity - First vertical derivative of (pre-conditioned) Bouguer gravity - Pseudo gravity - Pseudo magnetic - Trend - Trend consistency b) Model products (GoCad Tsurf, 3D dxf, and ModelVision tkm) - Magnetic depth-source models - Magnetic depth source solutions - Apparent susceptibility attributed magnetic source depth point set - Gridded depth to basement surface - Triangulated basement surface - Cover thickness c) Vector products (ESRI shape format) - Edge vectors (worms) from magnetic and gravity data - Contours - Basement surface contour vectors Note also: the following are some future survey-wide value-add products being planned for combined GCAS datasets - Lineaments and faults from magnetics and gravity - Magnetisation direction analysis of suitable anomalies - 3D inversion models of key anomalies Geographic Locality: North-central South Australia;2017 Gawler Craton Aerial Magnetic Survey (Region 2A);2017 Gawler Craton Aerial Radioactivity Survey (Region 2A);2017 Gawler Craton Aerial DEM Survey (Region 2A) Doc No: RB 2018/00015

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    Language English
    Metadata Standard ISO 19115-3

    Citations

    Use constraints License
    License Creative Commons Attribution 4.0
    Persistent identifier https://pid.sarig.sa.gov.au/document/2018d051203
    Citation Foss, C.A.;Gouthas, G.;Wise, T.;Katona, L.F.;Hutchens, M.F.;Reed, G.D. 2018. RB 2018/00015 Gawler Craton Airborne Geophysical Survey Region 2A, Murloocoppie – Enhanced geophysical imagery and magnetic source depth models. (Data zip file available from SAMRef). Exploration Initiative - Collaborative Exploration
    https://pid.sarig.sa.gov.au/document/2018d051203

    Technical information

    Status
    Maintenance and Update Frequency
    Geographic Reference GDA2020 (EPSG:7844)
    Geo bounding box {"type":"Polygon","coordinates":[[[133.5,-29],[135,-29],[135,-27.5],[133.5,-27.5],[133.5,-29]]]}
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