McFAULDS LAKE AREA
Ontario Airborne Geophysical Surveys Airborne Gravity Gradiometer and Magnetic Data Geophysical Data Set 1068
Ontario Geological Survey Ministry of Northern Development, Mines and Forestry Willet Green Miller Centre 933 Ramsey Lake Road, 7th Floor Sudbury, Ontario P3E 6B5 Canada and
Natural Resources Canada 615 Booth Street Ottawa, Ontario, K1A 0E4 Canada
Report on McFaulds Lake Airborne Geophysical Survey Geophysical Data Set 1068
CONTENTS
CREDITS ...... 2 DISCLAIMER ...... 2 CITATION...... 2 1. INTRODUCTION ...... 3 2. SURVEY LOCATION AND SPECIFICATIONS...... 4 SURVEY LOCATION...... 4 SURVEY SPECIFICATIONS...... 5 3. AIRCRAFT, EQUIPMENT AND PERSONNEL...... 7 AIRCRAFT AND GEOPHYSICAL ON-BOARD EQUIPMENT ...... 7 BASE STATION EQUIPMENT ...... 8 FIELD PERSONNEL ...... 8 4. DATA ACQUISITION...... 9 GENERAL STATISTICS ...... 9 5. DATA COMPILATION AND PROCESSING...... 11 PERSONNEL ...... 11 BASE MAPS ...... 11 PROCESSING OF BASE STATION DATA ...... 11 PRE-PROCESSING OF THE POSITIONING DATA ...... 11 PROCESSING OF THE POSITIONAL DATA ...... 11 PROCESSING OF MAGNETIC DATA ...... 12 PROCESSING OF GRAVITY DATA...... 12 FIRST AND SECOND VERTICAL DERIVATIVE OF THE RESIDUAL MAGNETICS ...... 14 KEATING CORRELATION COEFFICIENTS ...... 14 ADJUSTMENT TO THE RESIDUAL TOTAL MAGNETIC FIELD 200 M GRID OF CANADA ...... 15 6. FINAL PRODUCTS...... 16 7. QUALITY ASSURANCE AND QUALITY CONTROL...... 18 SURVEY CONTRACTOR ...... 18 QA/QC GEOPHYSICIST...... 19 MNDMF ...... 20 REFERENCES ...... 21 APPENDIX A. TESTING AND CALIBRATION...... 22 APPENDIX B. FIELD OPERATIONS SUMMARY ...... 29 APPENDIX C. PROFILE ARCHIVE DEFINITION ...... 30 APPENDIX D. KEATING CORRELATION ARCHIVE DEFINITION ...... 37 APPENDIX E. GRID ARCHIVE DEFINITION...... 38 APPENDIX F. GEOTIFF AND VECTOR ARCHIVE DEFINITION...... 39
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CREDITS This survey was carried out as a collaborative project between the Ontario Geological Survey (OGS) and the Geological Survey of Canada (GSC). The project was jointly funded by the Targeted Geoscience Initiative IV (TGI-4) and by the Ontario Government.
List of accountabilities and responsibilities: Jack Parker, Senior Manager, Precambrian Geoscience Section, Ontario Geological Survey (OGS), Ministry of Northern Development, Mines and Forestry (MNDMF) – accountable for the airborne geophysical survey projects, including contract management Régis Dumont, Geophysicist, Geological Survey of Canada, Natural Resources Canada –project management, quality assurance (QA) and quality control (QC) (GSC portion) Edna Mueller, Senior Geophysicist, Paterson, Grant & Watson Limited (PGW), Project Leader and QA/QC Geophysicist under contract to MNDMF – responsible for QA/QC (OGS portion) Shane Hefford, Geophysicist, Geological Survey of Canada, Natural Resources Canada –QA/QC deliverable products Tom Watkins, Data Manager, Information & Marketing Services Section, Ontario Geological Survey, MNDMF – manage the project-related hard-copy products Desmond Rainsford, Geophysicist, Precambrian Geoscience Section, Ontario Geological Survey, MNDMF – manage the project-related digital products Fugro Airborne Surveys Corp., Ottawa, Ontario – data acquisition and data compilation
DISCLAIMER To enable the rapid dissemination of information, this digital data have not received a technical edit. Every possible effort has been made to ensure the accuracy of the information provided; however, Natural Resources Canada and the Ontario Ministry of Northern Development, Mines and Forestry do not assume any liability or responsibility for errors that may occur. Users may wish to verify critical information.
CITATION Information from this publication may be quoted if credit is given. It is recommended that reference be made in the following form:
Ontario Geological Survey and Geological Survey of Canada 2011. Ontario airborne geophysical surveys, gravity gradiometer and magnetic data, grid and profile data (ASCII and Geosoft® formats) and vector data, McFaulds Lake area; Ontario Geological Survey, Geophysical Data Set 1068.
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1. INTRODUCTION The survey was flown under two separate contracts, between Fugro Airborne Surveys (FAS) and the GSC and between FAS and the OGS, covering different parts of the survey area. The airborne survey contracts were awarded through a Request for Proposal and Contractor Selection process. The system and contractor selected for each survey area were judged on many criteria, including the following:
applicability of the proposed system to the local geology and potential deposit types aircraft capabilities and safety plan experience with similar surveys QA/QC plan capacity to acquire the data and prepare final products in the allotted time price-performance
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2. SURVEY LOCATION AND SPECIFICATIONS
Survey Location The McFaulds Lake area is located in northwestern Ontario approximately 50 km east of the town of Webequie (Figure 1). The McFaulds Lake region is host to the “Ring of Fire” which is the term applied to a westward-concave Archean greenstone belt on the west edge of the James Bay Lowland in far northwestern Ontario (Figure 2). The roughly north-south-trending greenstone belt curves westward to form an arcuate-shaped belt. It is composed of mafic metavolcanic flows, felsic metavolcanic flows and pyroclastic rocks and a suite of layered mafic to ultramafic intrusions that trend subparallel with and obliquely cuts the westernmost part of the belt, close to a large granitoid batholith lying west of the belt. The major layered intrusion at its base, hosts Ni-Cu-PGE deposits of exceptional grade as well as overlying stratiform chromite deposits further east and higher in the layered intrusion stratigraphy. This main layered intrusion has been dated by the Jack Satterly Geochronology Laboratory for Noront Resources Ltd at about 2735 Ma. This is the same age as the felsic metavolcanic rocks that host the Cu- Zn deposits further east at McFaulds Lake (2737±7 Ma), implying that the layered intrusion near the base (western edge) of the belt would likely have served as a heat engine for these synvolcanic, hydrothermally generated Cu-Zn (VMS) deposits. The greenstone belt lies partially under a thin (few metres thick) cap of flat-lying Paleozoic carbonate rocks that thicken eastward.
Figure 1. McFaulds Lake region survey block flown with the Fugro Airborne Surveys gravity gradiometer and magnetic system shown in black outline.
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Figure 2. General geology of the McFaulds Lake area extracted from MRD 126 – Revision 1 (Ontario Geological Survey 2011), with locations of mineral deposits.
Survey Specifications The airborne survey and noise specifications in the McFaulds Lake region survey were as follows: a) traverse line spacing and direction flight line spacing is 250 m flight line direction is 135° maximum deviation from the nominal traverse line location could not exceed 50 m over a distance greater than 2000 m minimum separation between two adjacent lines could be no smaller than 175 m or larger than 325 m b) control line spacing and direction control line direction is 045° at regular 2500 m intervals, perpendicular to the flight line direction along each survey boundary (if not parallel with the flight line direction) maximum deviation from the nominal control line location could not exceed 50 m over a distance greater than 2000 m
Report on McFaulds Lake Airborne Geophysical Survey 5 Geophysical Data Set 1068 c) terrain clearance of the aircraft nominal terrain clearance is 100 m altitude tolerance limited to 15 m, except in areas of severe topography altitude tolerance limited to 10 m at flightline/control line intersections except in areas of severe topography d) aircraft speed nominal aircraft speed is 55 m/sec aircraft speed tolerance limited to 10 m/sec, except in areas of severe topography e) magnetic diurnal variation could not exceed a maximum deviation of 3 nT peak-to-peak over a chord of 60 seconds f) magnetometer noise envelope in-flight noise envelope could not exceed 0.1 nT, for straight and level flight base station noise envelope could not exceed 0.1 nT g) re-flights and turns all re-flights of flight line segments intersected at least two control lines all turns at the end of flight lines or control lines took place beyond the survey or block boundaries h) gravity standard deviation of half the difference between the two independent complements could not exceed 5 Eötvös for any survey line average speed along each survey line could not exceed 62 m/s if turbulence values exceeded 98 Gal for any survey line, or 88.2 Gal for three consecutive survey lines, the aircraft would return to base
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3. AIRCRAFT, EQUIPMENT AND PERSONNEL
Aircraft and Geophysical On-Board Equipment – Aircraft C-GGRD Aircraft: Cessna 208B
Operator: Fugro Airborne Surveys
Registration: C-GGRD
Mean Survey Speed: 54 m/s
Digital Acquisition: Fugro Digital Acquisition System (FASDAS) The Fugro FASDAS is a data acquisition system executing propriety software for the acquisition and recording of location, magnetic and ancillary data. Data are presented both numerically and graphically in real time on the VGA display providing on-line quality control capability.
FALCON™ AGG Data Acquisition System (ADAS) The Fugro DAS provides control and data display for the FALCON™AGG system. Data are displayed in real time for the operator and warnings displayed should system parameters deviate from tolerance specifications. All FALCON™ AGG and laser scanner data are recorded to a removable hard drive.
Gravity Gradiometer: The FALCON™ AGG System is based on current state-of-the-art airborne gravity gradiometer technology and has been optimized for airborne broad band geophysical exploration. The system is capable of supporting surveying activities in areas ranging from 1000 ft below to 13,000 ft above sea level with aircraft speeds from 70 to 130 knots. The FALCON™ AGG data streams were digitally recorded at different rates on removable drives installed in the FALCON™ AGG electronics rack.
Magnetometer: Scintrex CS-3 single cell caesium vapour, tail stinger installation, sensitivity = 0.005 nT, sampling rate = 0.1 s, ambient range 20,000 to 100,000 nT. The general noise envelope was kept below 0.1 nT. The nominal sensor height was ~100 m above ground.
Electronic Navigation: NovAtel OEMV-3G, 1 sec recording interval, with a resolution of 0.00001 degree and an accuracy of 5 m.
Laser Scanner: Riegl LSM-Q140i-80, 2-400 m measurement range, accuracy of 50 mm, laser wavelength of 0.9 μm, scan angle range is ±40°, scan speed of 20 scans/s.
Radar Altimeter: King KRA405, accuracy 2%, resolution 1 m, range 0 to 2500 ft, 0.1 sec recording interval.
Camera: Panasonic WVC484 digital video camera, Bullet digital video recorder.
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Base Station Equipment Magnetometer: Scintrex CS-2 single cell caesium vapour, mounted in a magnetically quiet area, measuring the total intensity of the earth's magnetic field in units of 0.01 nT at intervals of 0.5 sec, within a noise envelope of 0.20 nT.
GPS Receiver: NovAtel dual frequency Propak V3-L1/L2, measuring all GPS channels, for up to 12 satellites.
Computer: Laptop, Pentium model.
Field Personnel The following Fugro Airborne Surveys personnel were on-site during the acquisition program.
Cessna 208B: C-GGRD Andrew Campbell Pilot Cameron Sutcliffe Pilot Jesse Clayton Pilot Philippe Viotto Pilot Shawn Cowan Pilot Daniel MacDonald Electronics Technician and Operator Jason Loranger Electronics Technician and Operator Derek Rowney Aircraft Maintenance Engineer Jamie Harrison Aircraft Maintenance Engineer Todd Boughner Aircraft Maintenance Engineer
General project management was the responsibility of Jim Taggart, Fugro Airborne Surveys, in Ottawa, Ontario.
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4. DATA ACQUISITION The aircraft (C-GGRD) and airborne crew first mobilized to Webequie, Ontario (the base of operations) on January 25, 2011. This was followed by one day of setup, safety briefings, and ground runs. Data acquisition started on January 26, 2011 and continued well, averaging one flight per day, with few weather days. The high sensitivity magnetic base stations were set up at the Webequie logistics base camp, well away from cultural interference, in the field. The GPS base station antennas were mounted to the cabins at the Webequie logistics base camp. The exact location of the primary GPS base station was 52°58′05.08″ N and 87°22′07.12″ W at an elevation of 165.87 metres above the geoid. The exact location of the secondary GPS base station was 52°58′04.83″ N and 87°22′06.82″ W at an elevation of 164.93 metres above the geoid.
General Statistics Survey dates January 26, 2011 to March 14, 2011 Total km flown 19,733 km of gravity gradiometry and magnetics Total flying hours 171:30 (hours:minutes) Production hours 163:06 (hours:minutes) Number of production days 26 days Number of production flights 33 flights Bad weather days 2 days Magnetic diurnal days 1 day Testing and calibration 2 days Equipment breakdown 12 day Aircraft breakdown/maintenance 7 days Average production per flight 598 km per production flight Average production per hour 121 km per production hour Average production per day 759 km per production day
The following tests and calibrations were performed prior to the commencement of the survey: - Magnetometer lag - Magnetometer heading (cloverleaf) check - Magnetometer figure of merit (FOM) check - GPS navigation lag and accuracy check - Altimeter calibration
These tests were flown over the Geological Survey of Canada’s calibration range at Bourget, Ontario located near Ottawa.
Details of these tests and their results are given in Appendix A.
All digital data were verified for validity and continuity. The data from the aircraft and base station were transferred to the PC’s hard disk. Basic statistics were generated for each parameter recorded. These included the minimum, maximum and mean values, the standard deviation and any null values located. Editing of all recorded parameters for spikes or datum shifts was done, followed by final data verification via an interactive graphics screen with on-screen editing and interpolation routines.
The satellite navigation system with real time correction by CDGPS was used to ferry to the survey site and to survey along each line. Co-ordinates for the survey block were supplied by MNDMF and NRCan to establish the survey boundaries and the flight lines. Any other aircraft operating in the area were notified about the location of the survey block and flying height for safety concerns.
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The accuracy of the flight path guidance system is variable; depending on the number and condition of satellites employed, the raw GPS accuracy was for the most part better than 10 metres. Real-time correction using the CDGPS (broadcast services) improves the accuracy to about 3 metres or less.
A video camera recorded the ground image in AVI format along the flight path. A video display screen in the cockpit enabled the operator to monitor the flight path during the survey.
Checking all data for adherence to specifications was carried out in the office by an experienced Fugro Airborne Surveys data processor.
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5. DATA COMPILATION AND PROCESSING
Personnel The following personnel were involved in the compilation of data and creation of the final products: Jim Taggart Project Manager Mike Pearson Processing Manager David Murray Processing Supervisor Eric Rooen Processor/Product Preparation Darren Wilson Processor/Product Preparation Wayne Irvine Processor/Product Preparation
Base Maps Base maps of the survey area were supplied by Natural Resources Canada.
Projection description: Datum: North American Datum 1983 (NAD83) Local Datum: (4 m) Canada Ellipsoid: GRS80 Projection: UTM (Zone 16N) Central Meridian: 87° W False Northing: 0 m False Easting: 500,000 m Scale factor: 0.9996
Processing of Base Station Data The recorded magnetic diurnal base station data are converted from raw binary to ASCII and loaded into a Geosoft® OASIS database. After initial verification of the integrity of the data from statistical analysis, the appropriate portion of the data is selected to correspond to the exact start and end time of the flight. The data are then checked and corrected for spikes using a Median and Hanning noise filter of 0.5 seconds width. The filtered base station data are imported into the master airborne database based on common GPS time stamps. The long wavelength component of the diurnal signal is then extracted through an averaging filter of 71 seconds width.
Pre-Processing of the Positioning Data (GPS) The raw GPS data from both the aircraft and base station are recovered as binary files. The latitudes, longitudes and altitudes are converted from the WGS84 spheroid to the local map projection and datum (NAD83) in both geographic (decimal degree) and UTM (metre) co-ordinates. A point-to-point speed calculation is then done from the final X, Y co-ordinates and reviewed as part of the quality control. The flight data are then cut back to the proper survey line limits and a preliminary plot of the actual flight path is done and compared to the planned flight path to verify the navigation.
Processing of the Positional Data The positional data, which includes the radar altimeter, the laser scanner and the real-time corrected GPS elevation values, are checked and corrected for spikes using a fourth difference editing routine. The raw radar altimeter data are converted to metres using the calibrations determined from the altimeter flight test. There were no periods of poor satellite visibility that may affect the resolution of the GPS elevation values. The digital terrain elevation is computed by subtracting the laser scanner values from the differentially corrected GPS elevation values. Following a QC inspection, the DEM channel is gridded.
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Processing of Magnetic Data The binary raw data are reformatted and loaded into the Geosoft® OASIS database. After initial verification of the data by statistical analysis, the values are adjusted for system lag. The data are then checked and corrected for any spikes and gaps on the screen using a graphic profile display. Interactive editing, if necessary, is done at this stage. Following this, the long wavelength component of the diurnal is subtracted from the data and the mean diurnal value of each line added back as a pre-levelling step. A preliminary grid of the values is then created and verified for obvious problems, such as errors in positioning or bad diurnal. Appropriate corrections are then applied to the data, as required.
The final levelling process is applied to the data from the tail sensor. The first step consists of upward or downward continuing the magnetic values to the height of the drape surface used to fly the survey to compensate for the altitude variation of the aircraft. This is achieved by approximating the continuation (upward/downward) of the magnetic profile values using the Taylor expansion series. The process is applicable as long as the continuation distance remains small in comparison to the depth of the sources. This is the case for this survey since the standard deviation of the aircraft altitude with the drape surface is only 2.45 m compared to a minimum survey altitude of 100 m. (Pilkington and Thurston 2001). The final step is the tie line levelling which consists of calculating the positions of the control points (intersections of lines and tie lines), calculating the magnetic differences at the control points and applying a series of levelling corrections to minimize the mis-closures to zero and to do this to a maximum of intersections as possible. On this data set, 92.6% of the intersections were closed to zero. The grid of the traverse lines including control lines data, where intersections closed, is then calculated and checked for residual errors. Any gross errors detected are corrected in the profile database and the levelling process repeated. The grid was generated using the minimum curvature algorithm (Briggs 1974).
The International Geomagnetic Reference Field (IGRF) is calculated from the 2010 model year extrapolated to (March 1, 2011) at the mean survey altitude of 275 m asl and removed from the levelled values.
The residual total magnetic grid is then adjusted to the residual total magnetic field 200 m grid of Canada (see section 5 “Adjustment to the Residual Total Magnetic Field 200 m Grid of Canada”). This channel is then gridded using the minimum curvature algorithm at a cell size of 50 m.
Processing of Gravity Data The raw gravity data are extracted and checked by statistical analysis for performance evaluation including the use of a graphic profile display of data plots. LiDAR data are also verified to ensure valid returns and complete data coverage without gaps. Data are then compiled including system lags for further processing.
Post-processing is done to remove the effects of aircraft acceleration by modelling the acceleration of the gradiometer environment and removing sensitivities from the output. The gradient data are demodulated and filtered along line using a 6-pole Butterworth low-pass filter with a cut-off frequency of 0.18 Hz.
Gravity self-gradient is then calculated to reduce the time-varying gradient response from the aircraft and platform. The measurements from the gimbals on which the gradiometer is mounted provide the data for this calculation.
Final laser scanner processing includes using differential GPS and the gradiometer inertial navigation system data for pitch, roll and heading to reference the data to create an accurate digital terrain model. This model is used to remove the terrain effects for the absence of mass in relation to each data collection point and is calculated over a distance of 10 kilometres.
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The two corrected curvature components of the gravity tensor collected GNE (Northeast) and GUV, where GUV = (GEE-GNN)/2, are levelled using a least-squares minimisation of differences at survey line intersections.
Final transformation of the levelled data into gravity and components of the full gravity gradient tensor is accomplished using both the Fourier domain transformation and Equivalent source transformation.
Using the Fourier method, the data must be downward-continued and, in order to maintain stability, the data are low-pass filtered using a cut-off wavelength that is the smallest stable value considering variations in altitude and line spacing. The output generates all gravity tensor components.
The flight surface on which the data are collected is an irregular draped surface. To make possible the transformation of the horizontal curvature gradients GNE and GUV using Fourier domain potential field transfer functions requires that the data be located on a flat horizontal surface.
To achieve this, the data are piece-wise upward-continued to the top grazer, that is the peak elevation present in the flight surface. Following the transformation, the data are then moved back to a smoothed version of the flight surface via potential field continuation.
During the Fourier processing, the GNE and GUV data are first combined to produce data of the complex compound function GUV + i·GNE. The compound function is then converted to gD and GDD (and the other tensor components via similar formulae) according to the following equations: 2 2 1/2 -1 (kE + kN ) GD = FT 2 · FT []GUV + i·GNE ( kE,kN 0,0) (kE - i·kN)
-1 (kE + i·kN) GDD = FT · FT []GUV + i·GNE ( kE,kN 0,0) (kE - i·kN)
where kE, kN are the wave-numbers corresponding to the East and North directions FT, FT-1 specify the Fourier and inverse Fourier transform operations
The Equivalent source method relies on a smooth model inversion to calculate the density of a surface of sources and from these sources; a forward calculation provides the gradient tensor GDD and vertical gravity gradient gD data.
The sources are a layer of plates. The size of these plates is determined from the line spacing and usually a plate size of ¼ line spacing is used.
The source surface is also a smoothed version of the terrain surface and is located at an arbitrary depth below the terrain surface. Previous data sets have shown that placing the source surface at a depth equivalent to one line spacing below the terrain surface produces output gD and GDD data containing frequency and wavelength content closely matching those data resulting from the Fourier transformation.
The equivalent source method does not calculate all tensor components as does the Fourier method. Those calculated are gD, GDD, GNE and GUV.
The limitations of gravity gradiometry in reconstructing the long wavelengths of gravity can lead to differences in the results of these two methods. The merging of the gD data with the regional gravity from the 2 km Canada Gravity Database removes these differences.
The regional data are low-pass filtered using a cosine squared filter with cut-off at 30 km tapering to 20 km. The AGG gD data are high-pass filtered using a cosine-squared filter with cut-off at 30 km tapering to 20 km.
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First and Second Vertical Derivative of the Residual Magnetics The calculation of the first and second vertical derivative grids was done in the frequency domain without any low-pass filtering
Keating Correlation Coefficients Possible kimberlite targets are identified from the residual magnetic intensity data, based on the identification of roughly circular anomalies. This procedure is automated by using a known pattern recognition technique (Keating 1995), which consists of computing, over a moving window, a first-order regression between a vertical cylinder model anomaly and the gridded magnetic data. Only the results where the absolute value of the correlation coefficient is above a threshold of 75% were retained. On the magnetic maps, the results are depicted as circular symbols, scaled to reflect the correlation value. The most favourable targets are those that exhibit a cluster of high amplitude solutions. Correlation coefficients with a negative value correspond to reversely magnetised sources.
The cylinder model parameters are as follows: Cylinder diameter: 200 m Cylinder length: infinite Overburden thickness: 27.5 m (average) Magnetic inclination: 77° N Magnetic declination: 8° W Window size: 20 × 20 cells (1000m × 1000m) Magnetization scale factor: 100 Model window grid cell size: 50 m
An example of the model’s magnetic response is shown in Figure 3.
It is important to be aware that other magnetic sources may correlate well with the vertical cylinder model, whereas some kimberlite pipes of irregular geometry may not. The user should study the magnetic anomaly that corresponds with the Keating symbols, to determine whether it does resemble a kimberlite pipe signature, reflects some other type of source or even noise in the data, e.g., boudinage (beading) effect of the minimum curvature gridding. All available geological information should be incorporated in kimberlite pipe target selection.
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Figure 3. Vertical cylinder anomaly model used for Keating correlation. Top of cylinder outlined in blue. On the McFaulds Lake survey, the grid cell interval is 50 m and contour interval is 1 nT.
Adjustment to the Residual Total Magnetic Field 200 m Grid of Canada In summary, the levelled 50 m grid of the residual total magnetic grid was upward-continued to 305 m to be compared to the Canada grid. The difference grid was calculated and filtered to eliminate the short wavelengths. The resulting trend grid was then subtracted from the original residual total magnetic field grid, producing the adjusted grid. The trend grid was also subtracted from the levelled line data in the database. The theoretical aspects of the levelling methodology were fully discussed in Gupta et al. (1989) and Reford et al. (1990).
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6. FINAL PRODUCTS The following products were delivered to MNDMF and NRCan:
Map Products at 1:50,000 Scale Colour residual magnetic field grid with contours, plotted with flight path on a planimetric base Colour shaded image of the first vertical derivative of the residual magnetic field, plotted with Keating kimberlite coefficient anomalies and flight path on a planimetric base Colour conformed vertical gravity grid with contours, plotted with flight path on a planimetric base Colour vertical gravity gradient grid with contours, plotted with flight path on a planimetric base
Profile Database Gravity gradiometry database at 8 samples/s in Geosoft® GDB and ASCII format.
Magnetic database at 10 samples/s in both Geosoft® GDB and ASCII format.
Kimberlite Coefficient Database Keating kimberlite coefficient anomaly database in both Geosoft® GDB and ASCII CSV formats.
Data Grids Data grids, in both Geosoft® GRD and GXF formats, gridded from co-ordinates in NAD83 of the following parameters: Digital elevation model Residual magnetic field from the tail sensor Total magnetic field from the tail sensor First vertical derivative of the residual magnetic field from the tail sensor Second vertical derivative of the residual magnetic field from the tail sensor Drape surface for Fourier reconstruction, smoothed flight surface Drape surface for equivalent source construction, 100 m above terrain Fourier-derived vertical gravity (no terrain correction) Fourier-derived vertical gravity (terrain correction density 2.2 g/cc, 250 m cutoff wavelength, conformed & not conformed) Equivalent source–derived vertical gravity (terrain correction density 2.2 g/cc, conformed & not conformed) Fourier-derived GNE curvature gravity gradient (terrain correction density 2.2 g/cc, 250 m cutoff wavelength) Fourier-derived GUV curvature gravity gradient (terrain correction density 2.2 g/cc, 250 m cutoff wavelength) Fourier-derived GND horizontal N-S gravity gradient (terrain correction density 2.2 g/cc, 250 m cutoff wavelength) Fourier-derived GED horizontal E-W gravity gradient (terrain correction density 2.2 g/cc, 250 m cutoff wavelength) Fourier-derived GEE gravity gradient (terrain correction density 2.2 g/cc, 250 m cutoff wavelength) Fourier-derived GNN gravity gradient (terrain correction density 2.2 g/cc, 250 m cutoff wavelength) Fourier-derived GDD vertical gravity gradient (terrain correction density 2.2 g/cc, 250 m cutoff wavelength) Equivalent source–derived GDD vertical gravity gradient (terrain correction density 2.2 g/cc)
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GeoTIFF Images of the Entire Survey Colour residual magnetic field grid on a planimetric base Colour shaded image of the first vertical derivative on a planimetric base Colour conformed vertical gravity on a planimetric base Colour vertical gravity gradient on a planimetric base
DXF Vector Files of the Entire Survey Flight path Keating correlation (kimberlite) anomalies Residual field magnetic contours Conformed vertical gravity contours Vertical gravity gradient contours
Project Report Provided in both Microsoft® Word and Adobe® PDF formats.
Flight Videos The digitally recorded video from each survey flight are provided in a compressed binary format.
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7. QUALITY ASSURANCE AND QUALITY CONTROL Quality assurance and quality control (QA/QC) were undertaken by Fugro Airborne Surveys, PGW (QA/QC Geophysicist), the MNDMF and NRCan. Stringent QA/QC is emphasized throughout the project so that the optimal geological signal is measured, archived and presented.
Survey Contractor Important checks are required during the data acquisition stage to ensure that the data quality is kept within the survey specifications. The following lists in detail the standard data quality checks that were performed during the course of the survey.
Daily Quality Control Navigation Data: • The differentially corrected GPS flight track is recovered and matched against the theoretical flight path to ensure that any deviations are within the specifications (i.e., deviations not greater than 50 m from the nominal line spacing over a 2 km distance). • All altimeter data (radar and GPS elevation) are checked for consistency and deviations in terrain clearance are monitored closely. The survey is flown in a smooth drape fashion maintaining a nominal terrain clearance of 100 metres, whenever possible. A digital elevation trace, calculated from the laser scanner and the GPS elevation values, is also generated to further control the quality of the altimeter data. • The laser scanner data are examined for continuity and any gaps in the returns. Complete coverage of all survey lines is checked by looking at both profile and gridded data. • The synchronicity of the GPS time and the acquired time of the geophysical data is checked by matching the recorded time fields. • A final check on the navigation data is done by computing the point-to-point speed from the corrected UTM X and Y values. The computed values should be free of erratic behaviour showing a nominal ground speed of between 55 m/s with point-to-point variations not exceeding ±10 m/s.
Magnetometer Data: • The diurnal variation is examined for any deviations that exceed the specified 3 nT peak-to-peak over a 60 second chord. Data are re-flown when this condition is exceeded, with any re-flown line segment crossing a minimum of two control lines. A further quality control done on the diurnal variation is to examine the data for any man-made disturbances. When noted, these artefacts are graphically removed by a polynomial interpolation so that they are not introduced into the final data when the diurnal values are subtracted from the recorded airborne data. • The integrity of the airborne magnetometer data is checked through statistical analysis and graphically viewed in profile form to ensure that there are no gaps and that the noise specifications are met. • A fourth difference editing routine is applied to the raw data to locate and correct any small steps and/or spikes in the data. • Any effects of filtering applied to the data are examined by displaying, in profile form, the final processed results against the original raw data, via a graphic screen. This is done to ensure that any noise filtering applied has not compromised the resolution of the geological signal. • On-going gridding and imaging of the data is also done to control the overall quality of the magnetic data.
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Gravity Data: • During data acquisition, the average turbulence for a line must be less than 98 Gal or the pilot ceases production and returns to base. If three consecutive lines have turbulence in excess of 88.2Gal, the pilot also would return to base. • The post-mission compensation of the data is completed to verify proper operating parameters for the gradiometer throughout the flight. • Statistical analysis is performed to ensure noise values on both independent complements on all lines are below 5 Eötvös. Data are also checked for gaps and anomalous spikes.
Near-Final Products Near-final products of the profile and gridded navigation and magnetic data were made available to the QA/QC Geophysicist, for review and approval, prior to demobilization.
Quality Control in the Office Review of Field Processing of Gravity and Magnetic Data: The general results of the field processing are reviewed in the profile database by producing a multi- channel stacked display of the data (raw and processed) for every line, using a graphic viewing tool. The gravity, magnetic and altimeter data are checked for spikes and residual noise.
Review of Levelling of Magnetics: The results of the initial levelling of the magnetics are reviewed, using imaging and shadowing techniques. Any residual errors noted are corrected and the levelling re-applied to the profile data.
Creation of Second Vertical Derivative: The second vertical derivative is created from the final gridded values of the total field magnetic data and checked for any residual errors using imaging and shadowing techniques.
Interim Products: Archive files containing the raw and processed profile data and the gridded parameters are provided to the QA/QC Geophysicist for review and approval.
Creation of 1:50,000 Scale Maps: After approval of the interim data, the 1:50,000 scale maps are created and verified for registration, labelling, dropping weights, general surround information, etc. The corresponding digital files are provided to the Data Manager for review and approval.
QA/QC Geophysicist The QA/QC Geophysicist reviewed the data during data acquisition, focusing initially on the data acquisition procedures, base station monitoring and instrument calibration. As data were collected, they were reviewed for adherence to the survey specifications and completeness. Any problems encountered during data acquisition were discussed and resolved.
The QA/QC checks included the following:
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Navigation Data: • appropriate location of the GPS base station • flight line and control line separations are maintained, and deviations along lines are minimized • verify synchronicity of GPS navigation and flight video • all boundary control lines are properly located • terrain clearance specifications are maintained • aircraft speed remained within the satisfactory range • area flown covers the entire specified survey area • real-time corrected GPS data do not suffer from satellite-induced shifts or dropouts • GPS height and radar/laser altimeter data are able to produce an image-quality DEM • GPS and geophysical data acquisition systems are properly synchronized • GPS data are adequately sampled
Magnetic Data: • appropriate location of the magnetic base station, and adequate sampling of the diurnal variations • heading error and lag tests are satisfactory • magnetometer noise levels are within specifications • magnetic diurnal variations remain within specifications • magnetometer drift is minimal once diurnal and IGRF corrections are applied • spikes and/or drop-outs are minimal to non-existent in the raw data • filtering of the profile data is minimal to non-existent • in-field levelling produces image-quality grids of total magnetic field and higher order products (e.g., second vertical derivative)
Gravity Data: • turbulence values are within specifications • noise values for each complement does not exceed specifications • spikes and gaps are minimal to non-existent • proper time stamp verified with ancillary data • gradiometer environmental conditions are within acceptable operating conditions
The QA/QC Geophysicist and NRCan reviewed interim and final digital and map products throughout the data compilation phase, to ensure that noise was minimized and that the products adhered to the QA/QC specifications. This typically resulted in several iterations before all digital products were considered satisfactory. Considerable effort was devoted to specifying the data formats and verifying that the data adhered to these formats.
NRCan and MNDMF NRCan prepared all of the base map and map-surround information required for the hard-copy maps in consultation with the MNDMF. This ensured consistency and completeness for all of the geophysical map products. The base map was constructed from digital files of the 1:50,000 scale NTS map series.
MNDMF worked with the QA/QC Geophysicist and NRCan to ensure that the digital files adhered to the specified ASCII and binary file formats, that the file names and channel names were consistent, and that all required data were delivered on schedule. The map products were carefully reviewed in digital and hard-copy form to ensure legibility and completeness.
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REFERENCES Briggs, I. 1974. Machine contouring using minimum curvature; Geophysics, v.39, p.39-48.
Gupta, V., Paterson, N., Reford, S., Kwan, K., Hatch, D. and Macleod, I. 1989. Single master aeromagnetic grid and magnetic colour maps for the province of Ontario; in Summary of Field Work and Other Activities 1989, Ontario Geological Survey, Miscellaneous Paper 146, p.244-250.
Keating, P.B. 1995. A simple technique to identify magnetic anomalies due to kimberlite pipes; Exploration and Mining Geology, v.4, no.2, p.121-125.
Ontario Geological Survey 2011. 1:250 000-scale bedrock geology of Ontario; Ontario Geological Survey, Miscellaneous Release—Data 126 – Revision 1.
Pilkington, M. and Thurston, J.B. 2001. Draping corrections for aeromagnetic data: line-versus grid-base approaches; Exploration Geophysics, v.32, no.2, p.95-101.
Reford, S.W., Gupta, V.K., Paterson, N.R., Kwan, K.C.H. and Macleod, I.N. 1990. Ontario master aeromagnetic grid: A blueprint for detailed compilation of magnetic data on a regional scale; abstract in Expanded Abstracts, Society of Exploration Geophysicists, 60th Annual International Meeting, San Francisco, v.1, p.617-619.
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APPENDIX A. TESTING AND CALIBRATION
Cessna C-GGRD Lag Calibration Time offset (lag) is determined by flying perpendicular to a magnetic feature in opposing directions. A total of four passes were flown. Lag is then calculated based on distance between magnetic anomaly peaks (opposing directions) and speed. Data are then lagged by this amount of time to confirm that the magnetic anomaly peaks are lined up.
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Report on McFaulds Lake Airborne Geophysical Survey 23 Geophysical Data Set 1068
Radar Altimeter Calibration The radar altimeter was calibrated by acquiring altitude data from several passes over a flat surface (e.g., tarmac, lake). The radar data should show a linear relationship with the GPS height. A regression used to determine the linear equation that converts the radar data from its measured form in millivolts to metres above terrain.
GPSZ-Elevation vs Radar
350
300
250
200
150 GPSZ-Elevation (m) 100
50
0 -4500000 -4000000 -3500000 -3000000 -2500000 -2000000 -1500000 -1000000 -500000 0 Radar (mV) y = -0.000073248x + 0.566473376
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GPSZ-Elevation vs Radar
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300
250
200
150 GPSZ-Elevation (m) GPSZ-Elevation 100
50
0 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 Radar (m) y = 1.00000380x - 0.00000215
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Magnetometer Calibration The calibration of the magnetometer was carried out at the Bourget test site established by the Geological Survey of Canada near Ottawa. Aeromagnetic survey system calibration is flown in a “cloverleaf” pattern. This pattern allows the airplane to fly two passes in all four directions (N, S, E, W) while crossing over a single intersection point. For each pass (at the intersection point), magnetic data are recorded for both the airplane and on the ground (Bourget, Ontario). These data are then used to determine error values on each magnetometer for each direction as well as heading error effects.
A map showing the accuracy of all flight passes over the target intersection point is also shown below.
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Report on McFaulds Lake Airborne Geophysical Survey 27 Geophysical Data Set 1068
Magnetometer Figure of Merit Test Aircraft movements induce spurious magnetic fields, which are removed from the magnetic data by the compensator. The efficiency of this removal can be evaluated by conducting a test called a Figure of Merit (F.O.M.). The aircraft flies a series of three manoeuvres of ±10° rolls, ±5° pitches and ±5° yaws in each of the traverse and control line directions in a magnetically quiet zone (low magnetic gradient). The peak-to- peak amplitudes of the responses obtained on the magnetometer compensated channel are determined for each of the three manoeuvre types and for each of the four directions. The twelve values are then summed giving the Figure of Merit. This F.O.M. must be less than 1.5 nT for all sensors (wingtips and tail) or corrective action must be taken to minimize these spurious magnetic fields on the survey aircraft. The F.O.M. is determined at the beginning of the survey and repeated monthly or if a major change in aircraft or magnetometer equipment has occurred. The F.O.M. tests performed during the survey are presented hereafter.
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APPENDIX B. FIELD OPERATIONS SUMMARY The survey was performed by one aircraft, a Cessna 208B with registration C-GGRD, which flew all survey lines.
Job Summary
Maintenance 38%
Survey 52%
Setup 4%
Weather 6%
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APPENDIX C. PROFILE ARCHIVE DEFINITION Geophysical Data Set 1068 is derived from surveys using magnetic systems mounted on fixed wing platforms and carried out by Fugro Airborne Surveys Corp.
Data File Layout The files for the McFaulds Lake region Geophysical Survey 1068 are archived on a single DVD-ROM and sold as single product, as outlined below:
Type of Data Magnetic Grid/Vector and Profile data Format (DVD-R) ASCII and Geosoft® Binary 1068
The content of the ASCII and Geosoft® binary file types are identical. They are provided in both forms to suit the user’s available software. The survey data are divided as follows:
DVD - 1068 Line Data Archives: - ASCII Profile data - Profile database of magnetic data (10 Hz sampling) in ASCII (XYZ) format - Profile database of gravity gradiometry data (8 Hz sampling) in ASCII (XYZ) format - Profile database of Keating correlation (kimberlite) in ASCII (CSV) format
- Binary Profile data - Profile database of magnetic data (10 Hz sampling) in Geosoft® GDB format - Profile database of gravity gradiometry data (8 Hz sampling) in Geosoft® GDB format - Profile database of Keating correlation (kimberlite) in Geosoft® GDB format
Grid Files: - ASCII (GXF) grids - Digital elevation model - Residual magnetic field - Residual magnetic field (warped to 200 m Canada Grid) - Total magnetic field - First vertical derivative of the residual magnetic field - Second vertical derivative of the residual magnetic field - Drape surface for Fourier - Drape surface for equivalent source - Fourier-derived vertical gravity (no terrain correction) - Fourier-derived vertical gravity (terrain corrected, conformed & not conformed) - Equivalent source–derived vertical gravity (terrain corrected, conformed& not conformed) - Fourier-derived GNE curvature gravity gradient (terrain corrected) - Fourier-derived GUV curvature gravity gradient (terrain corrected) - Fourier-derived GND horizontal NS gravity gradient (terrain corrected) - Fourier-derived GED horizontal EW gravity gradient (terrain corrected) - Fourier-derived GEE gravity gradient (terrain corrected) - Fourier-derived GNN gravity gradient (terrain corrected) - Fourier-derived GDD vertical gravity gradient (terrain corrected) - Equivalent source–derived GDD vertical gravity gradient (terrain corrected)
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- Geosoft® Binary (GRD) grids: - Digital elevation model - Residual magnetic field - Residual magnetic field (warped to 200 m Canada Grid) - Total magnetic field - First vertical derivative of the residual magnetic field - Second vertical derivative of the residual magnetic field - Drape surface for Fourier - Drape surface for equivalent source - Fourier-derived vertical gravity (no terrain correction) - Fourier-derived vertical gravity (terrain corrected, conformed & not conformed) - Equivalent source–derived vertical gravity (terrain corrected, conformed & not conformed) - Fourier-derived GNE curvature gravity gradient (terrain corrected) - Fourier-derived GUV curvature gravity gradient (terrain corrected) - Fourier-derived GND horizontal NS gravity gradient (terrain corrected) - Fourier-derived GED horizontal EW gravity gradient (terrain corrected) - Fourier-derived GEE gravity gradient (terrain corrected) - Fourier-derived GNN gravity gradient (terrain corrected) - Fourier-derived GDD vertical gravity gradient (terrain corrected) - Equivalent source–derived GDD vertical gravity gradient (terrain corrected)
TIF Files: - GeoTIFF images (150 dpi) of the entire survey block - Colour shaded residual magnetic field grid on a planimetric base - Colour shaded image of the first vertical derivative on a planimetric base - Colour conformed vertical gravity on a planimetric base - Colour vertical gravity gradient on a planimetric base
Vector Files: - DXF - Flight path - Keating correlation (kimberlite) anomalies - Residual field magnetic contours - Conformed vertical gravity contours - Vertical gravity gradient contours
Report: - Logistics, processing and product documentation (Microsoft® Word and Adobe® PDF formats)
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Co-ordinate Systems The line data archives are provided in two co-ordinate systems: - Universal Transverse Mercator (UTM) projection, Zone 16N, NAD83, Canada local datum - latitude/longitude co-ordinates, NAD83, Canada local datum
The gridded data are provided in one UTM co-ordinate system: - Universal Transverse Mercator (UTM) projection, Zone 16N, NAD83, Canada local datum
Line Numbering The line numbering convention for survey 1068 is as follows:
• Line numbers in both the magnetics and gravity databases are 5 digits with the last digit indicating part or revision number: i.e., Line 10010 is the first line of the survey followed by line 10020; should line 10010 be in two parts the first is 10010 and the second is 10011. Should line 10020 have been reflown, it will be in the database as line 10021.
• The same convention is used for the labelling of the control lines. In the Geosoft® OASIS montaj™ binary databases, survey lines are designated with a leading character “L” and control lines are designated with a leading character “T”.
Profile Data The line data archives are provided in two formats, one ASCII and one binary:
ASCII These files were compressed using the WinZip® utility: ASCII XYZ file of magnetic data, sampled at 10 Hz - MCFMAG.xyz ASCII XYZ file of gravity gradiometry data, sampled at 8 Hz - MCFGRAV.xyz
Binary Geosoft® OASIS montaj™ binary database file (no compression) of magnetic data, sampled at 10 Hz - MCFMAG.gdb Geosoft® OASIS montaj™ binary database file (no compression) of gravity gradiometry data, sampled at 8 Hz - MCFGRAV.gdb
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The contents of MCFMAG.xyz/.gdb (both file types contain the same set of data channels) are summarized as follows:
Channel Name Description Units gps_x_raw raw GPS X metres gps_y_raw raw GPS Y metres gps_z_raw raw GPS Z (orthometric) metres gps_x_final differentially corrected GPS X (NAD83) decimal-degrees gps_y_final differentially corrected GPS Y (NAD83) decimal-degrees gps_z_final differentially corrected GPS Z metres above sea level x_nad83 easting in UTM co-ordinates using NAD83 metres y_nad83 northing in UTM co-ordinates using NAD83 metres long_nad83 longitude using NAD83 decimal-degrees lat_nad83 latitude using NAD83 decimal-degrees heading line heading degrees drape drape surface metres above sea level radar_raw raw radar altimeter metres above terrain radar_final corrected radar altimeter metres above terrain height calculated laser scanner clearance metres above terrain dem digital elevation model metres above sea level fiducial fiducial seconds flight flight number – line_number full flight line number (flight line and part numbers) – line flight line number – line_part flight line part number – time_1980 UTC time since January 6, 1980 seconds time_utc UTC time seconds time_local local time seconds after midnight date local date YYYYMMDD height_mag magnetometer height metres above terrain mag_baseA_raw raw magnetic primary base station data nanoteslas mag_baseB_raw raw magnetic secondary base station data nanoteslas mag_baseA_final corrected magnetic primary base station data nanoteslas mag_baseB_final corrected magnetic secondary base station data nanoteslas fluxgate_x X-component field from the compensation fluxgate nanoteslas magnetometer fluxgate_y Y-component field from the compensation fluxgate nanoteslas magnetometer fluxgate_z Z-component field from the compensation fluxgate nanoteslas magnetometer mag_raw_tail raw magnetic field from tail sensor nanoteslas mag_comp_tail compensated magnetic field from tail sensor nanoteslas mag_lag_tail compensated, edited and lag corrected magnetic field nanoteslas from tail sensor mag_diurn diurnal correction nanoteslas mag_diurn_tail diurnally corrected magnetic field from tail sensor nanoteslas mag_hc height correction nanoteslas mag_hc_tail height-corrected magnetic field from tail sensor nanoteslas mag_int intersection-based levelling correction nanoteslas mag_tot total levelling correction nanoteslas
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Channel Name Description Units mag_gsclevel_tail levelled magnetic field from tail sensor nanoteslas igrf local IGRF field nanoteslas mag_lev_tail residual magnetic field from tail sensor nanoteslas mag_warp_tail residual magnetic field from tail sensor adjusted to nanoteslas the 200 m Canada grid
The contents of MCFGRAV.xyz/.gdb (both file types contain the same set of data channels) are summarized as follows:
Variable Description Units gps_z_final differentially corrected GPS Z metres above sea level x_nad83 easting in UTM co-ordinates using NAD83 metres y_nad83 northing in UTM co-ordinates using NAD83 metres long_nad83 longitude using NAD83 decimal-degrees lat_nad83 latitude using NAD83 decimal-degrees heading line heading degrees drape drape surface metres radar_raw raw radar altimeter metres radar_final corrected radar altimeter metres height calculated laser scanner clearance metres dem digital elevation model metres fiducial fiducial seconds flight flight number – line_number full flight line number (flight line and part numbers) – line flight line number – line_part flight line part number – time_1980 UTC time since January 6, 1980 seconds TURBULENCE Estimated vertical platform turbulence Gal (vertical acceleration Gal) Err_NE NE gradient uncorrelated noise estimate, Eötvös after tie-line levelling Err_UV UV gradient uncorrelated noise estimate, Eötvös after tie-line levelling T_DD Terrain effect calculated for DD using a Eötvös density of 1 g/cc T_NE Terrain effect calculated for NE using a Eötvös density of 1 g/cc T_UV Terrain effect calculated for UV using a Eötvös density of 1 g/cc A_SJT_0_NE Self gradient, jitter corrected NE gradient, Eötvös no terrain correction A_SJT_0_UV Self gradient, jitter corrected UV gradient, Eötvös no terrain correction B_SJT_0_NE Self gradient, jitter corrected NE gradient, Eötvös no terrain correction B_SJT_0_UV Self gradient, jitter corrected UV gradient, Eötvös no terrain correction A_SJT_2p2_NE Self gradient, jitter & terrain corrected NE gradient, Eötvös terrain correction density 2.2 g/cc
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Variable Description Units A_SJT_2p2_UV Self gradient, jitter & terrain corrected UV gradient, Eötvös terrain correction density 2.2 g/cc B_SJT_2p2_NE Self gradient, jitter & terrain corrected NE gradient, Eötvös terrain correction density 2.2 g/cc B_SJT_2p2_UV Self gradient, jitter & terrain corrected UV gradient, Eötvös terrain correction density 2.2 g/cc A_SJT_2p67_NE Self gradient, jitter & terrain corrected NE gradient, Eötvös terrain correction density 2.67 g/cc A_SJT_2p67_UV Self gradient, jitter & terrain corrected UV gradient, Eötvös terrain correction density 2.67 g/cc B_SJT_2p67_NE Self gradient, jitter & terrain corrected NE gradient, Eötvös terrain correction density 2.67 g/cc B_SJT_2p67_UV Self gradient, jitter & terrain corrected UV gradient, Eötvös terrain correction density 2.67 g/cc gD_FOURIER_2p67 Fourier-derived vertical gravity, mGal terrain correction density 2.67 g/cc, 250 m cutoff wavelength GEE_FOURIER_2p67 Fourier-derived GEE gradient, Eötvös terrain correction density 2.67 g/cc, 250 m cutoff wavelength GNN_FOURIER_2p67 Fourier-derived GNN gradient, Eötvös terrain correction density 2.67 g/cc, 250 m cutoff wavelength GDD_FOURIER_2p67 Fourier-derived vertical gravity gradient, Eötvös terrain correction density 2.67 g/cc, 250 m cutoff wavelength GED_FOURIER_2p67 Fourier-derived GED horizontal EW gradient, Eötvös terrain correction density 2.67 g/cc, 250 m cutoff wavelength GND_FOURIER_2p67 Fourier-derived GND horizontal NS gradient, Eötvös terrain correction density 2.67 g/cc, 250 m cutoff wavelength GNE_FOURIER_2p67 Fourier-derived GNE curvature gradient, Eötvös terrain correction density 2.67 g/cc, 250 m cutoff wavelength GUV_FOURIER_2p67 Fourier-derived GUV curvature gradient, Eötvös terrain correction density 2.67 g/cc, 250 m cutoff wavelength DRAPESURFACE_FOURIER Drape surface for Fourier reconstruction, metres smoothed flight surface gD_FOURIER_2p2 Fourier derived vertical gravity, mGal terrain correction density 2.2 g/cc, 250 m cutoff wavelength GEE_FOURIER_2p2 Fourier-derived GEE gradient, Eötvös terrain correction density 2.2 g/cc, 250 m cutoff wavelength GNN_FOURIER_2p2 Fourier-derived GNN gradient, Eötvös terrain correction density 2.2 g/cc, 250 m cutoff wavelength GDD_FOURIER_2p2 Fourier-derived vertical gravity gradient, Eötvös terrain correction density 2.2 g/cc, 250 m cutoff wavelength GED_FOURIER_2p2 Fourier-derived GED horizontal EW gradient, Eötvös terrain correction density 2.2 g/cc, 250 m cutoff wavelength
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Variable Description Units
GND_FOURIER_2p2 Fourier-derived GND horizontal NS gradient, Eötvös terrain correction density 2.2 g/cc, 250 m cutoff wavelength GNE_FOURIER_2p2 Fourier-derived GNE curvature gradient, Eötvös terrain correction density 2.2 g/cc, 250 m cutoff wavelength GUV_FOURIER_2p2 Fourier-derived GUV curvature gradient, Eötvös terrain correction density 2.2 g/cc, 250 m cutoff wavelength gD_FOURIER_0 Fourier-derived vertical gravity, mGal no terrain correction applied, 250 m cutoff wavelength GEE_FOURIER_0 Fourier-derived GEE gradient, Eötvös no terrain correction applied, 250 m cutoff wavelength GNN_FOURIER_0 Fourier-derived GNN gradient, Eötvös no terrain correction applied, 250 m cutoff wavelength GDD_FOURIER_0 Fourier-derived vertical gravity gradient, Eötvös no terrain correction applied, 250 m cutoff wavelength GED_FOURIER_0 Fourier-derived GED horizontal EW gradient, Eötvös no terrain correction applied, 250 m cutoff wavelength GND_FOURIER_0 Fourier-derived GND horizontal NS gradient, Eötvös no terrain correction applied, 250 m cutoff wavelength GNE_FOURIER_0 Fourier-derived GNE curvature gradient, Eötvös no terrain correction applied, 250 m cutoff wavelength GUV_FOURIER_0 Fourier-derived GUV curvature gradient, Eötvös no terrain correction applied, 250 m cutoff wavelength gD_EQUIV_2p2 Equivalent source–derived vertical gravity, mGal terrain correction density 2.2 g/cc GDD_EQUIV_2p2 Equivalent source–derived vertical gravity gradient, Eötvös terrain correction density 2.2 g/cc GNE_EQUIV_2p2 Equivalent source–derived GNE curvature gradient, Eötvös terrain correction density 2.2 g/cc GUV_EQUIV_2p2 Equivalent source–derived GUV curvature gradient, Eötvös terrain correction density 2.2 g/cc DRAPESURFACE_EQUIV Drape surface for equivalent source construction, metres 100 m above terrain
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APPENDIX D. KEATING CORRELATION ARCHIVE DEFINITION
Kimberlite Pipe Correlation Coefficients The Keating kimberlite pipe correlation coefficient data are provided in two formats, one ASCII and one binary: ASCII comma-delimited format - MCFKC.csv Geosoft® OASIS montaj™ binary database file - MCFKC.gdb
Both file types contain the same set of data channels, summarized as follows:
Channel Name Description Units x_nad83 easting in UTM co-ordinates using NAD83 metres y_nad83 northing in UTM co-ordinates using NAD83 metres long_nad83 longitude using NAD83 decimal-degrees lat_nad83 latitude using NAD83 decimal-degrees corr_coeff correlation coefficient percent pos_coeff positive correlation coefficient percent neg_coeff negative correlation coefficient percent norm_error standard error normalized to amplitude percent amplitude peak-to-peak anomaly amplitude within window nanoteslas
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APPENDIX E. GRID ARCHIVE DEFINITION
Gridded Data The gridded data are provided in two formats, one ASCII and one binary: *.gxf - Geosoft® ASCII Grid eXchange Format (revision 3.0, no compression) *.grd - Geosoft® OASIS montaj™ binary grid file (no compression)
The grids are summarized as follows:
All grids are NAD83 UTM Zone 16 North, with a grid cell size of 50 m x 50 m.
- MCFDEM83.grd/.gxf – Digital Elevation Model - MCFRMAG83.grd/.gxf – Residual Magnetic Intensity - MCFR_WRP_MAG83.grd/.gxf – Residual Magnetic Intensity (Warped to 200 m Canada Grid) - MCFTMAG83.grd/.gxf – Total Magnetic Intensity - MCF1VD83.grd/.gxf – First Vertical Derivative of the Residual Magnetic Intensity - MCF2VD83.grd/.gxf – Second Vertical Derivative of the Residual Magnetic Intensity - MCFDFGRAV83.grd/.gxf – Drape Surface for Fourier - MCFDEGRAV83.grd/.gxf – Drape Surface for Equivalent Source - MCF_GD_FFT83.grd/.gxf – Fourier-derived Vertical Gravity (no terrain correction) - MCF_GD_FFT_TC_C83.grd/.gxf – Fourier-derived Vertical Gravity (terrain corrected & conformed) - MCF_GD_FFT_TC83.grd/.gxf – Fourier-derived Vertical Gravity (terrain corrected & not conformed) - MCF_GD_EQS_TC_C83.grd/.gxf – Equivalent Source–derived Vertical Gravity (terrain corrected & conformed) - MCF_GD_EQS_TC83.grd/.gxf – Equivalent Source–derived Vertical Gravity (terrain corrected & not conformed) - MCFGGGNE83.grd/.gxf – Fourier-derived GNE Curvature Gravity Gradient (terrain corrected) - MCFGGGUV83.grd/.gxf – Fourier-derived GUV Curvature Gravity Gradient (terrain corrected) - MCFGGGND83.grd/.gxf – Fourier-derived GND Horizontal N-S Gravity Gradient (terrain corrected) - MCFGGGED83.grd/.gxf – Fourier-derived GED Horizontal E-W Gravity Gradient (terrain corrected) - MCFGGGEE83.grd/.gxf – Fourier-derived GEE Gravity Gradient (terrain corrected) - MCFGGGNN83.grd/.gxf – Fourier-derived GNN Gravity Gradient (terrain corrected) - MCF_GDD_FFT_TC83.grd/.gxf – Fourier-derived GDD Vertical Gravity Gradient (terrain corrected) - MCF_GDD_EQ_TC83.grd/.gxf – Equivalent Source–derived GDD Vertical Gravity Gradient (terrain corrected)
All ASCII .gxf files were compressed using the WinZip® utility
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APPENDIX F. GEOTIFF AND VECTOR ARCHIVE DEFINITION
GeoTIFF Images Geographically referenced colour images, incorporating a base map, are provided in GeoTIFF format for use in GIS applications:
- MCFMAG83.tif – Shaded Levelled Residual Magnetic Intensity with Planimetric Base at 150 dpi (approximately 8.5 m per pixel) - MCF1VD83.tif – Shaded First Vertical Derivative of the Levelled Residual Magnetic Intensity with Planimetric Base at 150 dpi (approximately 8.5 m per pixel) - MCFBOGRAV83.tif – Conformed Vertical Gravity with Planimetric Base at 150 dpi (approximately 8.5 m per pixel) - MCFGGGDD83.tif – Vertical Gravity Gradient with Planimetric Base at 150 dpi (approximately 8.5m per pixel)
Vector Archives Vector line work from the maps is provided in DXF (v12) ASCII format using the following naming convention:
- MCFPATH83.dxf – Flight Path of the Survey Area - MCFKC83.dxf – Keating Correlation Targets - MCFMAG83.dxf – Contours of the Levelled Residual Magnetic Intensity in nanoteslas - MCFBOGRAV83.DXF – Contours of the Conformed Vertical Gravity - MCFGGGDD83.DXF – Contours of the Vertical Gravity Gradient
The layers within the DXF files correspond to the various object types found therein and have intuitive names.
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