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  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 nT apart in 50,000 nT field

345 346 Frequency, KHz 347

Narrow, symmetrical lines a key enabler of the technology Affect sensitivity and gradient tolerance … GEM developed gradient optimization procedures (2002) Sweep and “lock” on to first line

Potassium Principles -- Polarization 3

Spontaneous decay

2 1

RF Depolarization

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

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 5V EM Trigger input (On in 50 ms, Off 20 ms) • Data Acquisition (GEM Console or DAS) • Continues operation close to Transmitter Coil (minimum distance 1.5m

optimum 3m) • RS-232 Data Transfer (Optional) • GPS (20 Hz)

UAVs – Part of The Future  Unmanned Airborne Vehicles (UAV) offering new platforms for magnetic readings  Offer 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 pT /  Hz @ 20 samples per second • Resolution: 0.0001 nT • Absolute Accuracy: +/- 0.1 nT • Dynamic Range: 10,000 to 120,000 nT • Gradient Tolerance: 30,000 nT /m • Sensor Angle: Optimum angle 30  between sensor head axis and field vector • Heading Error: <0.05 nT between 10  rotation about axis to 80  and 360  full

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 ...