2 Volumes Final Proceedings - Washington 1984.pdf - IARC Research

212hydrochemical samples of the subsurface watersources and information on the geological-pennafrostand hydrogeological conditions, which canlater be studied using more labour-intensiveand comprehensive geophysical techniques. Traditionalgeophysical methods such as longitudinalelectroprofiling (most frequently two-differentialsymmetrical EP) and resistivimetry are themost widely used techniques in the initial stageof investigation (Dastovalov et al. 1979).Longitudinal profiling in the areas of naledformation is conducted along available streamchannels, since experience shows that thedevelopment of through taliks is most probable.The electroprofiling is conducted along the waterline, while for shallow streams and the channels itfollows the bends, crossing the headbands of theicings or subsurface water sources discoveredearlier. Thus, in the areas of subchannel talikicings the electroprofiles are established eitheralong the primary channel or along several channels, meters are used to detect the sources of subaqueousexiting beyond the outline of the naled formation discharge under deep river and lake basins.area. In the areas of flange and slope icing ofsubfrozen ground drainage, longitudinal profilingIn order to conduct traditional electroprofilingfor permafrost-hydrogeological studies in the icingis usually done from the primary river bed up the areas, natural field (NF) electroprofiling, whichstream running along the icing area and exitingbeyond its boundaries. In studies of those icingallows more accurate interpretation of other EPtypes and supplementary information on the zones ofareas, potentially related to the drainage of water subsurface water charging, movement and discharging,from mountain lakes located in upper valleys, the has been tested. an the whole, the informationelectroprofiles are established beginning with the value of this method is not very high and it servesshallow lake waters or the water line in the direc- only an auxiliary function in the overall electrotionof suspected drainage through the icing area, prospecting operations.etc.According to the results of longitudinal profil-In addition to traditional profiling methods usedin geophysical operations, more modern methods ofing, the areas of permafrost development are suf- electroprospecting, such as DEW (dipolar electroficientlydistinguished at ice crust base, well as magnetic profiling) and HFEP (high-frequency elecasthe through and blind taliks formed under the troprofiling), have been tested. A substantialstreams (Figure 2b). Preliminary analysis of the advantage of these methods, as compared with conresultsof longitudinal profiling is followed bythe establishment of individual non-extended transventionalEP, is their higher mobility combinedwith lower labor requirements (a team of 2-3verse profiles through the discovered taliks to persons); this is important for the large-scale anddelineate the taliks in the plan. Resistivimetrydata from longitudinal profiling, which providesinformation about the planned location of subsurfacetime-limited operations carried out in the zone ofBaikal-Amur Railway. The noncontact measurementmethod, which ensures the application under specifiwater sources, are used for the efficient distribu- conditions in areas of large-block deposits (stonetion of these profiles,streams, stone taluses and polygons, etc.), onResistivimetry, one of the most productive and surfaces covered with ice bodies and particularlyinformative geophysical techniques, makes it in operations carried out in winter, is equallypossible to distinguish among numerous occurrences important.of water in the test areas the ones that are related The experience of DEW application in differentto subsurface water discharge. It allows more spe- geological-frozen conditions is on the wholecific hydrochemical sampling, significant reduction indicative of its lower information content andof hydrosamples and preliminary estimation of the resolution as compared with EP the method usingrate of subsurface water mineralization (Afanasenko direct current. Using DE" data, the position ofet al. 1974).different geological and permafrost boundaries inDuring the permafrost-hydrogeological investiga- the plan can be identified, but the qualitativetions carried out in icing and subsurface water interpretation of these data is impeded. Otherdischarge areas, resistivimetry is carried out not substantial disadvantages of the method are theonly as point measurements of individual sources high screening effect of the thawed rocks, whichand other water manifestations (as an auxiliary makes it impossible to use it for studying deepmethod of hydrochemical sampling) but also as a taliks, and the strong dependence of the measuredvariation of stream electroprofiling. In this case values on the earth's surface relief, which resultsresistivimetry, like longitudinal profiling, is in false anomalies, unrelated to the geologicaldonecontinuously along the stream channels, exit- permafrost characteristics of the section. Foring beyond the icing area. Well differentiatedcurves of resitivimetric profiling (Figures 1 and2),which distinctly fix the sites of concentrated subsurfacewater discharge against a total backgroundof depleted solutions, can be obtained. The rateof mineralization of the surface, subsurface andmixed stream waters, together with the relativeoutput of subsurface water sources and a number ofother evaluation data, can be obtained using simplecalculations derived from these curves. Resistivimetricprofiling of a series of profiles having adense river network makes it possible to trace theflooded zones of individual fractures and tectonicdisturbances. These problems are more successfullysolved by magnetometry (Figure 2).Resistivimetric observations are carried outusing special portable meters based on combinedinstruments or electrothermometers and water scoopswith built in 4-electrode units (for water resistancemeasurement) and thermometers or thermo-resistors (for temperature measurement). Theresults of temperature measurements are used forqualitative estimation of surface and subsurfacewater mineralization rate and for their moreefficient identification. Benthonic resistivi-these reasons the DEMP method has not been usedindependently, but as an auxiliary method combinedwith other methods of electroprospecting.The HFEP method, elaborated in VSEGINGEO andtested earlier in Western Siberia (Timofeyev 19771,