Tomography of self-potential anomalies of electrochemical nature

Ore deposits and buried metals like pipelines behave as dipolar electrical geobatteries in which the source is due to (1) variation of the redox, pote ntial with depth, (2) oxido-reduction reactions acting at the ore body/grou ndwater contact, and (3) migration of electrons in the ore body itself betw een the reducing and oxidizing zones. This polarization mechanism is respon sible for an electrical field at the ground surface, the so-called self-pot ential anomaly. A new quick-look tomographic algorithm is developed to loca te electrical dipolar sources in the subsurface of the Earth from the analy sis of these self-potential signals. We applied this model to the self-pote ntial anomaly discussed by Stoll et al. [1995] in the vicinity of the KTB-b oreholes drilled during the Continental Deep Drilling Project in Germany. T he source of this self-potontial signal is related to the presence of massi ve graphite veins associated with steeply inclined fault zones within the g neisses and observed in the KTB-boreholes.