Developments and directions in 3D mapping of mineral systems using geophysics

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(See Geoscience Australia website - https://www.ga.gov.au/products/servlet/controller?event=GEOCAT_DETAILS&catno=70386 ). “Developments and directions in 3D mapping of mineral systems using geophysics” by Richard Lane (Geoscience Australia, richard.lane@ga.gov.au). Presented at “Science at the Surveys” (Melbourne, Victoria, Australia, 22 March 2010). The primary author would like to acknowledge the assistance of many people who have provided material and thoughts for this presentation, with special mention of Richard Chopping, Marina Costelloe, David Hutchinson, Nick Williams, and Lesley Wyborn. This presentation material will be included in a lecture that will be given in various South Pacific locations during 2011 as part of the Society of Exploration Geophysicists “Honorary Lecture Program” sponsored by Shell (http://www.seg.org/).

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Developments and directions in 3D mapping of mineral systems using geophysics

  1. 1. Developments and directions in 3D mapping of mineral systems using geophysics Richard Lane ( richard.lane@ga.gov.au ) Onshore Energy and Minerals Division Geoscience AustraliaScience at the Surveys, 22 March 2010
  2. 2. The DARPA Transparent Earth Project 2010-2015 has a vision that eloquently describeswhat we want to do!“… determine the physical, chemical, and dynamic properties of the Earth down to 5 km depth”  A global 3D volumetric model of physical/chemical properties and their variations with time  Data from multiple sensors inverted to estimate the properties  Changes determined at local scales and propagated back into the global model(N.B. DARPA = US Department of Defense - Defense Advanced Research Projects Agency) Science at the Surveys, 22 March 2010
  3. 3. These are the separate chapters in thispresentation but the issues are all interrelated1. Modelling and interpretation methods / Rock properties2. Next generation geophysical data acquisition3. Computing challenges • High performance computing (HPC) • Data and software interoperability • Visualisation and communication of 3D objects Science at the Surveys, 22 March 2010
  4. 4. 1. Modelling and interpretation methods / Rock propertiesRock properties are the keyThey are the link between geophysics and geology Science at the Surveys, 22 March 2010
  5. 5. Gravity or magnetics Rock property models Inversion ( Geologically constrained ) ( Litho- and alteration interpretation ) Rock property knowledge Geological observations Geological predictions Geological mapping( Adapted from slide by Nick Williams ) © Geoscience Australia
  6. 6. GA carry out lithological and alteration mappingusing several different methods.Some are based on property models derived though inversion a. Thresholding b. Qualitative alteration mapping c. Quantitative alteration mapping d. Multi-property litho-classificationOthers are based on litho-modelling methods that use geological subdivisions rather than properties as the primary variables e.g., GeoModeller, VPmg, IGMAS, ModelVision, etc Science at the Surveys, 22 March 2010
  7. 7. Thresholding of density inversion results from NW Queensland Blue = low density ≈ granite Orange = high density ≈ mafic/ultramafic/Fe-rich/sulphides( Adapted from slide by Richard Chopping ) © Geoscience Australia
  8. 8. Qualitative and quantitative alteration mapping results for the Ernest Henry-Eloise area Qualitative method Quantitative method( Adapted from slide by Richard Chopping ) © Geoscience Australia
  9. 9. Measurements of complementary rock properties allow multi-property regions to be defined for each rock type for use in litho-classification. HistogramsMagnetic susceptibility (SI) Ultramafic Sulphides Granite Mafic Density (g/cm3) Density (g/cm3) ( Adapted from slide by Nick Williams ) © Geoscience Australia
  10. 10. Outcrop mapping GSWA & GA ( Adapted from slide by© Geoscience Australia Nick Williams )
  11. 11. Litho-classification voxet model ( Adapted from slide by© Geoscience Australia Nick Williams )
  12. 12. Litho-classification voxet model ( Adapted from slide by© Geoscience Australia Nick Williams )
  13. 13. Some useful references for the work shownabove. GA Record 2009/29 https://www.ga.gov.au/products/servlet/controller?e vent=GEOCAT_DETAILS&catno=69581 Ph.D. thesis by Nick Williams Williams, N. C., 2008, Geologically-constrained UBC– GIF gravity and magnetic inversions with examples from the Agnew-Wiluna greenstone belt, Western Australia: Ph.D. thesis, University of British Columbia, 478p. http://hdl.handle.net/2429/2744 Selected papers Williams, N. C., 2009, Mass and magnetic properties for 3D geological and geophysical modelling of the southern Agnew–Wiluna Greenstone Belt and Leinster nickel deposits, Western Australia: AJES, 56, 1111 – 1142. Williams, N.C., and Dipple, G.M., 2007, Mapping subsurface alteration using gravity and magnetic inversion models: In Milkereit, B., Proceedings of Exploration 07: Fifth Decennial International Conference on Mineral Exploration, 461-472. Science at the Surveys, 22 March 2010
  14. 14. GeoModeller 3D geological mapping and litho-inversion example : Capel and Faust Basins 10 km Water (1.03 g/cm3) GA-302 Line 019 Build a 3D geological model from each generation of 2D Upper sediment (1.90 g/cm3) seismic interpretation Middle sediment (2.20 g/cm3) Use 3D visualisation to aid Lower sediment (2.40 g/cm3) structural analysis Evaluate each model using Basement (2.70 g/cm3) gravity data and litho- + … Mantle (3.10 g/cm3) Simplified seismic interpretation inversion 450 km 520 km Seismic line locations 3D geological model (Water and Basement units not shown) © Geoscience Australia
  15. 15. Start GeoModellerlitho-inversion Load geological and property models geometry optimisation Propose changes to the models process Fail Apply geological tests Pass Fail Forward model and apply geophysical tests Pass (Modifications rejected, (Modifications accepted and saved) revert to previous models) Continue? © Geoscience Australia Finish
  16. 16. 200 km Colour range of 45 mGal for each imageObserved data Calculated data * * Based on the model at proposal 4 million Geometry optimisation of vertical gravity to refine basin thickness (and Moho interface) (mGal)Misfit © Geoscience Australia
  17. 17. Geometry optimisation to refine basin thickness (and Moho interface) Images of basin thickness (m) Colour range of 0 to 5 km shown in both imagesPrior model 285 km Water (1.03 g/cm3) Sediments (2.42 g/cm3) 30 km Basement (2.70 g/cm3) Mantle (3.05 g/cm3) Animation of model evolutionPosterior model Frames at 20k intervals, 0 to 4M proposals Vertical section 302-02, Vertical exaggeration 5 : 1 © Geoscience Australia
  18. 18. 2. Next generation geophysical data acquisitionRegional airborne electromagnetic surveys (AEM)Airborne gravity surveys (AG)Airborne gravity gradiometer surveys (AGG)We require better facilities and methods to characterise the many different systems that are available or under development Science at the Surveys, 22 March 2010
  19. 19. Location of the Kauring Test Site shown on aregional vertical gravity image. Perth * (Geodetic projection, GRS80 Spheroid, GDA94 Datum) © Geoscience Australia
  20. 20. A ground gravity survey was carried out in 2009 to providehigh quality semi-regional and detailed data for the KauringTest Site, WA. m ~ 100 k Kauring © Geoscience Australia
  21. 21. A regional view of the ground gravity data (~150 x 150 km,2 km spacing) reveals terrain boundaries and broadgeological subdivisions. (MGA50 projection, GDA94 Datum) © Geoscience Australia
  22. 22. A semi-regional view of the ground gravity data (~20 x 20km, 500 m spacing) reveals geological units with higherresolution. (MGA50 projection, GDA94 Datum) © Geoscience Australia
  23. 23. “Airborne Gravity 2010” WorkshopPart of the 2010 ASEG-PESA Conference 22nd August 2010 in the Blackwattle Bay Room, Level 1 Crown Plaza Darling Harbour Register on http://www.aseg-pesa2010.com.au/Themes – Operating airborne gravity and gravity gradiometry systems – Systems under development – Advances in processing and interpretation software – Complementary technologies Science at the Surveys, 22 March 2010
  24. 24. 3. Some of the computing challenges …High performance computing (HPC)Data and software interoperabilityVisualisation and communication Science at the Surveys, 22 March 2010
  25. 25. Time required for regional gravity and magnetic inversions TOTAL: ~3 months 2 months data management 7. Interpreting results 2 weeks** computing time 2 weeks “science” 1. Synthesising 6. "Final" inversion 2 weeks physical property data 1 day 3 weeks 5. Testing geological 2 weeks 1 week constraints 2. Geophysical data preparation 1 week Continuous North Queensland: 3 weeks inversion 2800 CPU hours iterations (54 hours/day) 3. Choosing Gawler (so far): 4. Building geological inversions 700 CPU hours( Adapted from slide constraints parameters (63 hours/day) by Nick Williams ) © Geoscience Australia
  26. 26. Data stores User Computing Resources (Local computer, local network, online) Knowledge / Experience (Local computer, local network, online) Geology Background prior information Geophysics Rock propertiesData processing Geosoft MATLAB Probabilistic Intrepid Others … How do I navigate through this? 3D geological model (consistent with all data)DET CRC Mineralogy Provenance (Metadata / Audit Trail etc.) / Lithology / Rock property software Gravity Magnetics Electrical EM Seismic Others … Geological mapping Geophysical modelling GeoModeller Gocad 3DMove Vulcan Datamine EVS & MVS GeoModeller UBC-GIF VPmg ModelVision Intrepid Target PA (Profile Analyst) Fugro-LCT GMSys IGMAS Potent Others … Discover 3D Others … © Geoscience Australia
  27. 27. Data stores User Computing Resources (Local computer, local network, online) Knowledge / Experience (Local computer, local network, online) Geology Background prior information Geophysics Rock properties I want to … Discover data setsData processing Download or Link to data View, Analyse & Process Geosoft MATLAB (repeat this) Probabilistic Intrepid Others … Export a result 3D geological model Document the Workflow (consistent with all data)DET CRC Mineralogy Provenance (Metadata / Audit Trail etc.) / Lithology / Rock property software Gravity Magnetics Electrical EM Seismic Others … Geological mapping Geophysical modelling GeoModeller Gocad 3DMove Vulcan Datamine EVS & MVS GeoModeller UBC-GIF VPmg ModelVision Intrepid Target PA (Profile Analyst) Fugro-LCT GMSys IGMAS Potent Others … Discover 3D Others … © Geoscience Australia
  28. 28. Data stores User Computing Resources (Local computer, local network, online) Knowledge / Experience (Local computer, local network, online) Geology Background prior information Geophysics Rock properties Workflow Computing Data Manager Manager Resource Manager Templates / Wizards Availability & Access Controls Recording & ReportingData processing Geosoft MATLAB Probabilistic Intrepid Others … Central Interface Export 3D geological model Discovery (consistent with all data) Visualisation FunctionsDET CRC Mineralogy Analysis Provenance (Metadata / Audit Trail etc.) / Lithology / Rock property software Geophysical Modelling Interface Geological Mapping and Visualisation Interface Gravity Magnetics Electrical EM Seismic Others … Geological mapping Geophysical modelling GeoModeller Gocad 3DMove Vulcan Datamine EVS & MVS GeoModeller UBC-GIF VPmg ModelVision Intrepid Target PA (Profile Analyst) Fugro-LCT GMSys IGMAS Potent Others … Discover 3D Others … © Geoscience Australia
  29. 29. CRC for Deep Exploration Technologies“To improve deep ore discovery by opening upboth greenfields and brownfields search spacethrough quicker, more effective exploration atdepth and through cover” Science at the Surveys, 22 March 2010
  30. 30. Data stores User Computing Resources (Local computer, local network, online) Knowledge / Experience (Local computer, local network, online) Sub‐project 2.3.1 Geology Background prior information Geophysics Rock properties Sub‐project 2.3.3 Workflow Computing Data Manager Manager Resource Manager Su Co Recordingb/‐Reporting Templates Wizards Availability & Access Controls Data processing Int mp & pro erp uter jec Geosoft MATLAB ret  Aid t 2 Probabilistic .3. atiSub‐project 2.3.2 Central Interface ed G Export Intrepid Others … 4 3D geological model Discovery on (consistent with all data) Visualisation  Pr eol Functions Analysis oje ogi Provenance DET CRC Mineralogy ct ( cal (Metadata / Audit Trail etc.) / Lithology / Rock CA   property software GI) Geophysical Modelling Interface Geological Mapping and Visualisation Interface Gravity Magnetics Electrical EM Seismic Others … Geological mapping Geophysical modelling GeoModeller Gocad 3DMove Vulcan Datamine EVS & MVS GeoModeller UBC-GIF VPmg ModelVision Intrepid Target PA (Profile Analyst) Fugro-LCT GMSys IGMAS Potent Others … Discover 3D Others … © Geoscience Australia
  31. 31. Computation blowout Standard GA study: • 3D gravity & magnetic inversions GA status • 600 km x 600 km to 25 km depth Stone Age Bronze Age Iron Age “Petascale” (Desktop) (Condor) (NCI) Age? Largest on @ current @ higher @ ideal single PC resolution resolution resolution Data spacing/ 3.75 km x 3.75 km 2 km x 2 km 400 m x 400 m 80 m x 80 m model cell size (1 obs. / 14 km2) (1 obs. / 4 km2) (6 obs. / km2) (156 obs. / km2) Number of data 25,600 90,000 2.25 million 56.25 million Number of model cells 640,000 2.25 million 281.25 million 35.1 billion Memory required 3.2 GB 40 GB 115 TB 351 PB Required CPU time 4 hours 48 hours 17 years 52,500 years Run time 2 CPUs: 24 CPUs: 6,000 CPUs: ??? 2 hours 2 hours 12 hours 100 CPUs: ??? 62 days( Adapted from slide by Nick Williams ) © Geoscience Australia
  32. 32. Gravity example : Olympic Dam, SA 10 km 10 km Olympic Dam Olympic Dam Acropolis Acropolis Wirrda Well Wirrda Well Cell size: 2 km x 2 km x 1 km Cell size: 250 m x 250 m x 200 m 1 cell = 320 cells( Adapted from slide by Nick Williams ) © Geoscience Australia
  33. 33. Virtual Exploration Geophysics (Computing) Laboratory Combination of data stores, software and computers Based on the ‘Cloud Computing’ paradigm Users do not need to know where data is stored Resources are available as a fee for service 3D Tools NT Inversion Tools Extend the concept to QLD commercial cloud Visual Mesh isation Tools WA NSW facilities SA VIC TAS GA e.g., Google cloud services, Amazon EC2 and S3, Microsoft Azure, etc.( Adapted from slide by Lesley Wyborn ) © Geoscience Australia
  34. 34. Visualisation and communication of 3D geologicalmaps and geophysical models remains a challenge.Full 3D mapping and GIS programs e.g., gOcadViewers e.g., Geocando, ParaviewGeoCustomised interfaces e.g., VRML, X3DOther e.g., Movies, 3D PDFVirtual globes e.g., Google Earth, WorldWind Science at the Surveys, 22 March 2010
  35. 35. Pro et contra for Google Earth• Provides location and scale context for the content• Input data are in an international OGC standard format – KML and KMZ• Spherical geometry – Latitude, longitude, and elevation (m) – Simple cylindrical projection (Plate Carrée, or EPSG:4326 projection) with WGS84 datum• Includes the 4th dimension (time)• Supports multi-resolution data views• Supports point, line, polygon, and image feature types• Supports use of cloud-based data files• Very large client base• Good interface• Lacks true 3D volumetric object support• Standard viewer does not support sub-surface data Science at the Surveys, 22 March 2010
  36. 36. Google Earth example : Kauring Test Site regionalvertical gravity image © Geoscience Australia
  37. 37. Google Earth example : Kauring Test Site regionaland semi-regional ground gravity observation sites © Geoscience Australia
  38. 38. Google Earth example : Kauring Test Site regionaland semi-regional ground gravity observation sites © Geoscience Australia
  39. 39. Google Earth example : Kauring Test Site regionaland semi-regional ground gravity observation sites © Geoscience Australia
  40. 40. Google Earth example : GAP-P1 global P-wave seismic tomography model sections and slices( GAP-P1 model - See Obayashi et al., 2006 ) © Geoscience Australia
  41. 41. Google Earth example : GAP-P1 global P-wave seismic tomography model sections and slices( GAP-P1 model - See Obayashi et al., 2006 ) © Geoscience Australia
  42. 42. We have reviewed various developments anddirections in 3D geological mapping using geophysicalmodellingWe have seen that anumber of interrelatedissues are beingaddressed.  Modelling and interpretation methods Magnetic susceptibility (SI)  Rock properties  Data  High performance computing  Data and software interoperability Density (g/cm3)  Visualisation and communication Science at the Surveys, 22 March 2010

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