Geophysical Surveys

Question 1

Gravity suverys

Answer 1

•gravimeter measures small variations in gravitational field strength in milli gals
•Data corrected for latitude, altitude and topography
•Gravity maps plotted with isogals and anomalies identified
•positive anomaly indicates high density, negative low density

Question 2

Magnetic surveys

Answer 2

•magnetometer used to measure small variations in magnetic field strength in nano Tesla
•minerals rich in iron produce positive anonalies

Question 3

Electromagnetic surveys

Answer 3

•measure ground conductivity by electromagnetic induction
•Em waves induce currents in conducting materials such as metallic ore minerals

Question 4

Electrical resistivity surveys

Answer 4

•two electrodes placed in ground and an electric current is passed through them
•low resistance indicates good conductors and thus metallic ore minerals

Question 5

Geochemical surveys

Answer 5

Stream sediment sampling, soil sampling, water sampling, vegetation sampling

Question 6

Stream sediment sampling

Answer 6

Downstream of source will have anomalous metal values, upstream will have normal metal values

Question 7

Soil sampling

Answer 7

Soil samples on top and downslope of the source will have anomalous metal values, upslope will have normal metal values

Question 8

Vegetation sampling

Answer 8

•biogeochemical surveys analyse the trace element content of selected plant species
•geobotanical surveys involve mapping the distribution of an indicator plant species that can tolerate high concentrations of a particular metal

Question 9

Geophysical surveys

Answer 9

Gravity surveys, magnetic surveys, electromagnetic surveys, electrical resistivity surveys

Question 10

Water sampling

Answer 10

Increase in metal content may indicate presence of metallic mineral deposits nearbly