ELECTRICAL METHODS OF GEOPHYSICAL EXPLORATION OF MINERAL DEPOSITS.pptx

Various electronic methods for geophysical mineral exploration

1. ELECTRICAL METHODS OF GEOPHYSICAL EXPLORATION OF MINERAL DEPOSITS PRESENTATION BY: ANKITA SAHOO M.Sc. 1 st year (2 nd 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., E lasticity D ensity M agnetism E lectrical conductivity R adioactivity

4. Different types of geophysical exploration 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:- Self polarization method Equipotential method Electromagnetic method Resistivity method 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 VOLTAGE TIME CURRENT ON CURRENT OFF t0 t1 t2 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

21. THANK YOU