Abstract: A method of exploration for deposits of oil, gas and of other minerals in the earth including geothermal energy, which is based on the existence of electrotelluric currents that are generated spontaneously by such deposits because of the geochemical modifications caused by their presence within rocks in the proximity of such deposits, which method consists in measuring the magnetic perturbations created by said electrotelluric currents in the normaly existing earth magnetic field.When such electrotelluric currents exist, closed line-integrals of the earth magnetic field performed at or near the earth's surface so not vanish and the residual values of such integrals are a direct function of the magnitude and of the polarity of the electrotelluric current flux densities generated by the underground mineral deposits sought.