Exploration of chrome ore in Southwestern Turkey by VLF-EM

M. Bayrak

Geophysical Engineering Department, Istanbul University, Avcilar Campus, 34850 Istanbul, Turkey

E-mail: mbayrak@istanbul.edu.tr

(Received 21 May 2001; accepted 30 August 2001)

Abstract: Geophysical exploration for chrome ore deposits is rather complicated, and integrated geophysical methods should be used. For an integrated data interpretation respective data sets has been collected from VLF-EM (“Very Low Frequency”-electromagnetic), induced polarization (IP), gravity, magnetic and self potential (SP) data in southwestern Turkey. This area is known for its occurrence of chrome ore. VLF-EM parameters such as the apparent resistivity, phase, real and imaginary components of the vertical magnetic field and tilt angle of the magnetic polarization ellipse were acquired using 16 kHz (GBR, Rugby, England) radio signal. Mapping of the VLF-EM resistivity, phase, real component of vertical magnetic field and filters (Fraser filter, 1969 and Karous and Hjelt filter, 1983) yields good results in distinguishing conducting ore bearing fault zones within the resistive ultrabasic rocks. The dominant feature of the reconnaissance mapping is that the low values of resistivities (<100 Ohm.m) extend in about N 25o E direction. This characteristic direction correlated with the extension of known chrome occurrences in the field. Displaying of the VLF-EM real 2-D current density pseudosections along three profiles, secondary currents were followed with depth in the ground.

Key Words: Chrome Ore, VLF-EM, Integrated Geophysics, Southwestern Turkey