Electrical surveys using the method of the natural electrical field; new investigations

Ogilvy, A. A.; Ostrovskij, E. J.; Ruderman, E. N.

doi:10.1007/bfb0011655

Cited by 8 publications

(4 citation statements)

References 30 publications

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“…The anomalous effect of the former is much more dramatic, so that an ore anomaly usually cannot be distinguished. Disseminated sulfide ores almost do not occur in SP fields because of the isolating influence of intergranular substance (Ogil'vi et al, 1987;Ryss, 1983;Semenov, 1974;Sveshnikov, 1967;and others).…”

Section: Regional Metamorphism Of Kordamentioning

confidence: 95%

The Blagodatnoe gold-sulfide deposit (Yenisei Ridge, Russia): the nature of geophysical anomalies and the succession and causes of formation of petrophysical zoning

Kolmakov

2014

Russian Geology and Geophysics

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Data on geophysical fields and petrophysical heterogeneity, parageneses and the thermodynamic conditions and age of their formation, and fluid inclusions were used for the genetic reconstruction of petrophysical zoning at the Blagodatnoe gold-sulfide deposit. Petrophysical associations of the preore and ore stages of the deposit formation are clearly reflected in anomalies of the magnetic and natural electric fields and the aureoles of radioactive elements. At the early preore stage (752 Ma), reduced solutions with high activity of K, enriched in U, Th, and, probably, Au, were supplied to intensely foliated tectonic zones. Their interaction with initial metasedimentary rocks gave rise to contiguous zones of quartz-muscovite and chlorite metasomatic rocks. Accompanying graphitization led to a high electrochemical activity of the metasomatic rocks, which generated anomalies of up to -300 mV in the natural electric field; the most intensely carbonized zones became enriched with U (up to 6.5 × 10 -4 %) and, probably, Au. The quartz-muscovite metasomatic rocks accumulated Th and K (up to 29 × 10 -4 % and 4%, respectively), whereas the chlorite metasomatic rocks accumulated rock-forming elements (particularly Fe), which led to the compaction of these rocks and the acceleration due to gravity in local positive anomalies. The nonmagnetic character of the fresh pre-ore metasomatic rocks suggests the predominantly pyritic composition of early sulfides. At the ore stage (698 Ma), the minerals were deposited from H 2 O-CO 2 -As-S solutions at 560 to 315 ºC. The activity of these solutions caused a redistribution of radioactive elements and a high petrophysical differentiation of the ore-bearing structure. The amplitudes of the anomalies above this structure vary from 500 to 80 nT in the magnetic field and from -130 to +10 mV in the natural electric field. It has been found that the hydrothermal fluid hardly affected the polarization properties of graphitized rocks at the maximum temperatures but caused an intense removal of U and the development of magnetic pyrrhotite after pyrite. The temperature decrease in the mineral-forming system was favorable for the formation of siderite. Carbonaceous schists which experienced carbonatization lost their electrochemical activity. The binding of carbon dioxide in the solid phase influenced the migration capability of trace elements and their zonal distribution. With this evolution of the solution, Th accumulated at the lower levels of the mineralized zone, whereas the upper levels of the deposit became enriched with U. Productive gold-arsenopyrite-pyrite-pyrrhotite paragenesis with anomalous magnetic susceptibility evolved at the ore stage. The late galena-sphalerite-chalcopyrite paragenesis (365 Ma) was of strictly local occurrence and reduced the magnetic susceptibility of ores.

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Section: Regional Metamorphism Of Kordamentioning

confidence: 95%

The Blagodatnoe gold-sulfide deposit (Yenisei Ridge, Russia): the nature of geophysical anomalies and the succession and causes of formation of petrophysical zoning

Kolmakov

2014

Russian Geology and Geophysics

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“…It would be the inverse situation if the source was electrokinetic. We can therefore deduce that SP measurements in the Nsimi watershed are essentially the results of an electrochemical phenomenon, which is characteristic of clay-rich formations (Ogilvy et al, 1988) such as lateritic covers. To confirm this hypothesis, correlations were carried out between SP and percentage of clay in the weathering mantle.…”

Section: Correlation Between Sp and Elevation: Hypothesis On The Sourmentioning

confidence: 98%

Self-potential anomalies in the lateritic cover of the Nsimi watershed in southern Cameroon: origin and influence of electrical and granulometric parameters

Atangana

Nyeck

Bitom

et al. 2003

Journal of Applied Geophysics

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“…On the other hand, in order to invert the measured SP anomaly, which means to calculate the depth of the horizontal flow, it is important to have in mind that the physical system of the subsurface flow at the contact of the two layers is equivalent to a system of dipoles oriented perpendicularly to the contact, as Ogilvy et al [16] have pointed out. Therefore, the inverse problem consists in determining the location of the underground dipole current sources.…”

Section: Introductionmentioning

confidence: 99%

The Self-Potential Anomaly Produced by a Subsurface Flow at the Contact of Two Horizontal Layers and Its Quantitative Interpretation

Skianis

2012

International Journal of Geophysics

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In the present paper the problem of a polarized cylinder with a small cross-section, which is located at the contact of two horizontal layers with different resistivities, is studied. Such a polarization geometry simulates the self-potential (SP) field produced by a horizontal flow at the contact between the two layers. First, the expression of the self potential at the space domain is derived, applying the image technique. Then, the expression for the Fourier transform of the SP anomaly is found and the behavior of the amplitude spectrum is studied. Based on this study, a direct interpretation method at the spatial frequency domain is proposed, in order to calculate the depth of the flow and the reflection coefficient of the stratified medium. Experimentation with a synthetic model shows that the method works well (small deviations between true and calculated values). When the SP curve contains noise, deviations between calculated and true depths are smaller than those between calculated and true reflection coefficients. The proposed method, which is also applied on SP data from a geothermal system (Mauri et al., 2010), may be useful in detecting underground water or heat flows.

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Electrical surveys using the method of the natural electrical field; new investigations

Cited by 8 publications

References 30 publications

The Blagodatnoe gold-sulfide deposit (Yenisei Ridge, Russia): the nature of geophysical anomalies and the succession and causes of formation of petrophysical zoning

The Blagodatnoe gold-sulfide deposit (Yenisei Ridge, Russia): the nature of geophysical anomalies and the succession and causes of formation of petrophysical zoning

Self-potential anomalies in the lateritic cover of the Nsimi watershed in southern Cameroon: origin and influence of electrical and granulometric parameters

The Self-Potential Anomaly Produced by a Subsurface Flow at the Contact of Two Horizontal Layers and Its Quantitative Interpretation

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