Electric and electromagnetic methods

Question 1

What are these methods used for?

Answer 1

For mineral exploration, hydrological and ground contamination surveys, archaeological surveys.

Question 2

What is special about resistivity (DCR) method?

Answer 2

It uses Direct Current
It investigates variations of electrical resistivity by injecting an electrical current into the ground (using wire) and measuring potential differences

Question 3

What is induced polarisation (IP) method used for?

Answer 3

Used for mineral prospecting specially for disseminated ores which is hard to detect with other geo-electrical methods. Disseminated ore is an ore containing small particles of valuable minerals, spread quite uniformly throughout the host rock

Question 4

What is special about the Self Potential (SP) method?

Answer 4

Used for prospecting for massive ores and relies on natural electro-chemical processes that generates potential differences in the subsurface

Question 5

What is special about the electromagnetic induction (EM) method?

Answer 5

Uses alternating current to produce electromagnetic fields. Surveying usually does not use wires connected to the ground. Currents in cables are alternating (Frequency domain methods) or transient (Time domain methods). Uses intermediate frequency ranges.

Question 6

What is special about Ground Penetrating Radar (GPR)?

Answer 6

Records ground penetrating radar waves (high frequencies), a type of electromagnetic wave, reflected from subsurface. Limited to top few meters of subsurface

Question 7

What is special about MagnetoTelluric (MT) method?

Answer 7

Utilizes natural low frequency sources which provide deep penetration of the current system into the ground