Development of Airborne Potassium Magnetometer Dr Ivan Hrvoic

Development of Airborne Potassium Magnetometer Dr. Ivan Hrvoic, Ph. D. , P. Eng. President, GEM Advanced Magnetometers Exploration 2007 & KEGS

Overview · Airborne Trends in Mineral Exploration · Why Develop Potassium? · Solutions and Examples · Fixed Wing · Helicopter and EM · UAV · Summary

Airborne Trends in Mineral Exploration Last 5 years has seen a number of key trends that affect the implementation of any new airborne technology: 1. High Resolution Data 2. More Information from Data 3. Better Positioned Data 4. Safe Acquisition 5. Cost Effective Acquisition

Why Develop Potassium? Reflects industry trends: • High Resolution – Sensitivity, Sampling, Low Heading Error • Good Gradient Measurements – Absolute Accuracy • Positioning – Integrate with GPS • Safety – Implement on Any Platform • Cost Effective – Gradient Arrays

Potassium Principles -- Spectal Lines 4 Narrow Spectral Lines approximately 100 n. T apart in 50, 000 n. T field Narrow, symmetrical lines a key enabler of the technology 345 346 Frequency, KHz 347 Affect sensitivity and gradient tolerance … GEM developed gradient optimization procedures (2002) Sweep and “lock” on to first line

Potassium Principles -- Polarization Absorption Light Polarization 3 Spontaneous decay 2 1 RF Depolarization

Potassium Principles -- Sensor Circular Polarizer Photo measurement K-lamp Filter Potassium bulb

Solutions and Examples. Fixed Wing – Solutions • Sensor (Single or Multiple) • Electronics • Pod and / or Stinger • Data Acquisition Console (GEM or 3 rd Party) • Pilot Guidance (Optional 3 rd Party) • RS-232 Data Transfer (Optional) • GPS • Altimeter (Optional)

Fixed Wing -- Installation

Helicopter – Solutions • Sensor (Single or Multiple) • Electronics • Towed Bird (Single or Multiple Sensors) • Tow Cable • Data Acquisition Console (GEM or 3 rd Party) • RS-232 Data Transfer (Optional) • GPS

Helicopter – Magnetics Data Silver exploration, Mexico

Gradiometers - Rationale • Focusing on increased spatial resolution and detail; small anomalies on the flanks of large features can be clearly resolved • Vertical gradient information used in vertical gradient maps, analytic signal maps and Euler products • Longitudinal and horizontal gradient used to improve the accuracy and resolution of magnetic maps • Detection of even the smallest source can be achieved with a line spacing of up to 2 times height above magnetic source (Scott Hogg, et al, 2004)

Tri-Directional Gradiometer – Bird Fins are spaced at 120 degrees to allow for simple calculation of gradients in all three directions: • Average magnetic field of the two lower fins falls beneath the upper fin sensor to allow for vertical gradient calculation • Average of all three sensors falls in the centre of the bird shell to allow for simple determination of along-track gradient • Two lower fins used to calculate across-track gradient

Tri-Directional Gradiometer -- Bird

Tri-Directional Gradiometer Data

Improved Resolution of Small Targets

Raw Profiles – Vertical Gradient Data

Helicopter EM – Solutions • Sensor (Magnetometer or Gradiometer) • Support for 5 V EM Trigger input (On in 50 ms, Off 20 ms) • Data Acquisition (GEM Console or DAS) • Continues operation close to Transmitter Coil (minimum distance 1. 5 m optimum 3 m) • RS-232 Data Transfer (Optional) • GPS (20 Hz)

UAVs – Part of The Future ØUnmanned Airborne Vehicles (UAV) offering new platforms for magnetic readings ØOffer advantages of high resolution data, low level surveys over remote and offshore targets, reduced operator risk

UAV – Components • Sensor (Single or Multiple) • Electronics • Data Acquisition Console (GEM or 3 rd Party) • RS-232 Data Transfer (Optional) • GPS (20 Hz)

Base Stations – Capabilities Overhauser or Potassium base stations available for effective elimination of diurnals: • Precise time synchronization of airborne and base station units using a built-in GPS option • Multiple modes of operation: • Flexible (up to 30 periods) • Daily (specify daily hours) • Immediate (start instantly)

Potassium – Specifications • Sensitivity: 4 p. T / Hz @ 20 samples per second • Resolution: 0. 0001 n. T • Absolute Accuracy: +/- 0. 1 n. T • Dynamic Range: 10, 000 to 120, 000 n. T • Gradient Tolerance: 30, 000 n. T /m • Sensor Angle: Optimum angle 30 between sensor head axis and field vector • Heading Error: <0. 05 n. T between 10 to 80 and 360 full rotation about axis

SUMMARY • Airborne magnetics – Industry always seeking new technologies with additional benefits • Potassium offers substantial improvements in sensitivity and in other parameters • Results demonstrate the effectiveness of the system for high resolution magnetic and gradiometric mapping

Thank you for your attention. . .