Spontaneous Polarization Studies*

An offshore self‐potential array, towed behind a small boat, has recorded anomalies of up to −300 mV. These anomalies were related to conductive onshore deposits, and appear to be caused by offshore extensions of the deposits. Along with locating onshore deposits and their offshore extensions, the system may be useful for locating offshore deposits with no onshore extension. The background noise level of the system typically is a few tenths of a millivolt, allowing reliable recording of one millivolt gradient anomalies under average sea conditions.

Section: Offshore Depositmentioning

confidence: 99%

“…This mechanism does not require the minerals of the deposit to react chemically, as they serve only as the medium to transfer electrons toward a region of more oxidizing Eh. A laboratory experiment demonstrating that an Eh gradient across a conductive body can cause current flow in the body was performed by Becker and Telford (1965).…”

Section: Offshore Depositmentioning

confidence: 99%

Offshore Use of the Self‐potential Method*

Corwin

1976

“…Finally it is recognized that mechanisms other than the geochemical model are required to explain SP-anomalies in sedimentary basins (e.g. Becker and Telford 1965). Anomalies related to groundwater migration have been identified by Bogoslovsky and Ogilvy (1973), and fault planes are readily defined in regions subject to geothermal activity (e.g.…”

Section: Sp-fieldsmentioning

confidence: 99%

Self Potential and Current Channelling*

Cull¹

1985

CULL, J.P. 1985, Self Potential and Current Channelling, Geophysical Prospecting 33, 46& 467.Anomalies in self potential (SP) are usually explained in terms of geochemical activity. However, there are other sources of current which cause complications in the interpretation. In particular, DC telluric currents can be generated outside the survey region. Contrasts in resistivity cause current channelling and secondary voltages can be induced by leakage. The effect can be demonstrated using network theory and internal sources can be emphasized by subtraction. Joint surveys are required to demonstrate correlations with apparent resistivity.

“…A great deal of field evidence deriving from borehole measurements (e.g. Becker and Telford 1965;Parasnis 1970; Logn and Bolviken 1974;Kayal, Datta and Madhusudan 1982) suggests that it is fundamentally unsuited to model the mineral self-potentials inside the source body itself. Additionally, the simple source distributions employed by the model have also been criticized for being obscure in terms of the underlying electrochemical causation (Fitterman 1978;Sill 1983;Eskola and Hongisto 1987).…”

Section: Introductionmentioning

confidence: 99%

A RECONCILIATION OF MATHEMATICAL MODELS FOR SPONTANEOUS MINERALIZATION POTENTIALS¹

Furness

1993

Two methods for computing spontaneous mineralization potentials in the region external to the source body are reviewed. The first of these is a long‐established technique in which the causation is assumed to be a distribution of simple current source on the boundary of the mineralization. The second is a more recent technique which assumes a surface distribution of current dipole moment (double layer) along the boundary of the source body. The former technique is a special case of a more general spontaneous potential (SP) model in which the source is a density of current dipole moment (current polarization) distributed throughout the mineralization. As far as the potentials in the region external to the source body are concerned this current polarization can be simply related to an equivalent double layer source function, i.e. the potential discontinuity produced over the boundary of the mineralization by an equivalent double layer model. This simple relationship suggests an integral equation technique for the exact numerical solution of boundary value problems appropriate to the polarization model for spontaneous mineralization potentials. The technique is applied to exploring the justification of interpreting mineralization self‐potentials by the traditional approach.