Integrated Geochemical and Geophysical Approach to Mineral Prospecting – A Case Study on the Basement Complex of Ilesa Area, Nigeria - Advances in Data, Methods, Models and Their Applications in Geoscience - page 81

conductive overburden seriously suppresses response from basement conductors,
andrelatively small variations in overburden conductivity or thickness can themselves
generate significant VLF anomalies. For this reason, VLF is more effective in areas where the
host rock is resistive and the overburden is thin.
In the VLF method, two orthogonal components of the magnetic field were measured, and
normally the tilt angle, α, and ellipticity, e , of the vertical magnetic polarization ellipse are
derived. Real (in-phase) and imaginary (quadrature) are used in the Karous - Hjelt Fraser
filter (KHFFILT) programme. These components are based on the tilt angle, (α) and
ellipticity (e) as:

Re =tan (α) 100% and Im = e 100%. (1)

VES No Layer Resistivity

(Ω -m)

Layer thickness
(m)

Curve type Remark

1 231

368
892
233

3. 77
6. 01
13. 50
-

AK AMP*

2 127

439
104
324

0. 59
2. 23
13. 28
-

KH AMP

3 795

202
455
3065

1. 03
11. 45
7. 68
-

HA AMP

4 407

257
49
320

0. 60
2. 11
4. 87
-

QH GMU

5 350

177
445
238

1. 13
1. 80
36. 43
-

HK GMU

6 550

1195
1804
186

0. 50
6. 28
25. 03
-

AK SEC

7 330

455
2212
319

1. 26
6. 16
22. 82

AK QQS

*AMP = AmphiboliteGMU = Gneiss and Migmatite Undifferentiated
QQS = Quartzite/Quartz Schist SEC= Schist and Epidiorite Complex
Table 5. Geoelectric layer parameters of the study area