Various electronic methods for geophysical mineral exploration

1. ELECTRICAL METHODS OF
GEOPHYSICAL EXPLORATION OF
MINERAL DEPOSITS
PRESENTATION BY: ANKITA SAHOO
M.Sc. 1st year (2nd Semester)
Roll no.-22GEOL013

2. CONTENTS:
 Introduction
 Different methods of geophysical exploration
 Different electrical methods of geophysical
exploration
 Conclusion
 References

3. INTRODUCTION
 Geophysical exploration is associated with
detecting changes in geological conditions that may
be directly or indirectly related to economic mineral
deposit.
 The five important geophysical methods relate to
the five most common characteristics of the earth,
which can be determined from the surface viz.,
i. Elasticity
ii. Density
iii. Magnetism
iv. Electrical conductivity
v. Radioactivity

4. DIFFERENT TYPES OF GEOPHYSICAL
EXPLORATION METHODS
Seismic
methods
Gravity
methods
Electrical
methods
Radioactive methods
Magnetic
methods

5. ELECTRICAL METHODS OF GEOPHYSICAL
SURVEY OF MINERAL EXPLORATION
All electrical methods are widely used in the
exploration work connected with metalliferous
deposits, in prospecting of groundwater and in
investigations done for construction of engineering
structures.
These methods include:
i)electrical conductivity or resistivity
ii)electro chemical activity
iii)dielectric constant( depends on the capacitance of
the rock and its static response to the applied field)

6. The different electrical methods include:-
A. Self polarization method
B. Equipotential method
C. Electromagnetic method
D. Resistivity method
E. Induced polarisation method

7. 1. SELF POLARISATION METHOD
 Also known as “Spontaneous polarisation”
method.
 Utilises natural flow of current.
 Useful for locating elongated magnetite and
sulphide deposits.
 Operates on the fundamental principle that an
ore body undergoing oxidation is a source of
electric current or telluric current.

8. 2. EQUIPOTENTIAL METHOD
 Best suited for shallow deposits.
 Can be used to locate ore bodies in glacial drift and
for determining structures beneath the soil.
 If an ore body is present then there is distortion in the
equipotential lines.
 Hence by noting the distortion in the equipotential
lines, the hidden ore body can be demarcated.

9. 3. ELECTROMAGNETIC METHOD
 More precise and yields greater information.
 When an AC current is passed through a conductor,
induced currents are produced around it. If a
conductor, such as an ore body, within the induced
field it sets up a secondary induced currents around it
which can be measured.
 Used for reconnaissance survey.

10. 4. RESISTIVITY METHOD
 In resistivity method current is passed into the
ground by metallic (Cu) electrodes and potential
difference is measured.
 Apparent resistivity is measured.
 It is carried out using 3 ways:-
A) Wenner configuration
B) Schulmberger configuration
C) Dipole- dipole method

11. A) WENNER CONFIGURATION:

12. Two types of resistivity surveys are carried out:
a) Resistivity trenching or traversing
Used to investigate variations of rock beds in the
horizontal direction at constant depth.
b) Resistivity sounding
The variation is recorded in vertical direction.
Used for greater depth.

13. RESISTIVITY TRENCHING

14. RESISTIVITY SOUNDING

15. B) SCHLUMBERGER CONFIGURATION

16. C) DIPOLE- DIPOLE METHOD

17. 5. INDUCED POLARIZATION METHOD
 It has been observed that in resistivity survey that on
disconnecting the battery from current electrodes the
voltage in potential electrodes doesn't generally drop
to zero immediately but persists for some time with a
continuously decreasing magnitude. This
phenomenon is called IP.

18. TYPES OF I.P. SURVEY :
TIME DOMAIN I.P.
SURVEY
FREQUENCY DOMAIN I.P.
SURVEY
V
V A
V
O
L
T
A
G
E
TIME
CURRENT
ON CURRENT
OFF
t0 t1t2 t3

19. CONCLUSION
The geophysical methods are very useful for mineral
exploration.
They can be implemented with other exploration to increase
the accuracy as well as preciseness.
 The electrical methods can be used for the exploration of
metalliferous deposits of iron( hematite, magnetite), sulphide
deposits etc.
These method can also be implemented for the exploration
of groundwater and also for studying the rock properties
which is important for the construction of engineering
structures.

20. REFERENCES
 Principles of engineering geology- K.M.BANGAR
 Courses in mining geology- R.N.P. AROGYASWAMY
 Essentials of mineral exploration and evaluation-
S.M.GANDHI &B.C.SARKAR
 Mineral exploration principles and applications-
S.K.HALDAR
 Ignou university study material
 Google images