Self potentials at the Joma pyrite deposit, Norway

Abstract

SP-patterns both in drill holes and at the surface are separated into two parts: 1. (1) a general trend indicating the dipole pattern in the country rock around the deposit with maximum potential variations approximately 200 mV; and 2. (2) alternating potentials, with minima down to −800 mV in the massive sulphides, the steep gradients of which indicate EMF's at the country-rock/sulphide interfaces. Sulphides and country rock are supposed to constitute galvanic cells of which the sulphides represent dipole electrodes, and the pore water of the country rock the electrolyte. The redox potential of the pore water decreases with depth. Separation of the SP potential pattern into two dipole systems offers possibilities for: 1. (1) locating possible extentions of ore bodies with depth; li(2) rough estimations of tonnage of total ore bodies if the tonnage of upper parts are known; and 2. (3) estimations of sulphide contents of ore sections without analyzing drill cores or drilling cuts. The concept of the galvanic cell indicates that electrochemical processes to some extent control the dispersion of chemical elements around ore deposits.