Electronic Geophysical Surveys LirJted, 250 South Fell Avenue, North Burnahy 2, B. C. Telenhone:

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1 L GEOWG GEOPIIYSICAL SEPORT #IlO of the Gaichon Contact Group of Claims!. 1 mile NNbJ of Max&$ Lake, B.C. 50 North Vest for 4": "~ II' George Saarse Aup,, Aug. 29, 1964 D. L. Hings, P. Eng. -1 i Electronic Geophysical Surveys LirJted, 250 South Fell Avenue, North Burnahy 2, B. C. Telenhone:

2 ELECTRONIC GEOPHYSICAL SURVEYS LIMITED Vancouver. B.C. March 18th INTRODUCTION The Geomag method is a means of measuring telluric current distribution laterally by magnetic instrumentation. Geomag constitutes a means of measuring in the atmosphere, the influence of current distribution in the ground to derive resistive values. Geomag Characteristics The Geomag method is based on the premise that the diurnal magnetic variations in the declination and inclination are a result of the earth s telluric field influencing the earth s magnetic field. The relative readings from each station are determined by observing a sequence of several readings to establish a mean value. This value is representative of the local telluric current influence, on the I and D angles of the magnetic field. The arbitrary resistive profile is obtained from the phase relation of the I and D profiles from the traverse readings. Readings obtained under two diurnal conditions establish the static magnetic value. The more familiar ground contact method of magnetotelluric surveying, utilizing the oscillatory potentials or micropulsations. depends upon the interpretation of synchronous passive wave recording. The Geomag method utilizes the mean DC level between any existing micropulsations, with the relative station I and D readings along the traverse being interpreted from periods of synchronous monitoring control. The advantages of the greater depth measurements from tellurics are combined with the faster instrumentation of magnetics in the Geomag method. The limitations of varying azimu.th potentials in the ground contact magnetotelluric method, are a beneficial factor to the Geomag method.

3 Geomag Method -2- March 1Hth GEOMAG METHOD MEASUREMENT AND INTERPRETATION OF MINERAL DEPOSITS A survey involves making accurate measurements of the magnetic field inclination and declination components to form profiles from equivalent spaced stations. These traverse measurements are made quickly and precisely by the Geomag instrument with a special electronic amplifier. A general impression of the survey results may be obtained on site from the direct measurements, but a more detailed interpretation is necessary, to derive specific results of which the system is capable. Telluric Currents, an Anomalous Factor in the Geomag Measurements the report. The following facts concerning telluric currents are pertinent to the rest of (al Telluric currents flow within the earth s surface and extend well into the earth s crust. The current density at any location depends on the distribution of the current, which is directly related to the resistivity of the formations carrying the currents. (bl Telluric currents penetrate to great depths due to their inherently extremely W low frequency. This means that, in the detection system described, ore bodies may also be located at depths that are beyond the range of any system that depends on externally applied energy. (cl Telluric currents will consistently be greater in sulphide ore deposits than in the surrounding rock which is essentially composed of dielectric material. The concentration of polarizing currents associated with the ore body results in the production of an induced secondary magnetic field. (dl The secondary magnetic field set up by the ore body creates characteristic anomalies in the earth s magnetic field components, which are detected by the Geomag system, Technique Since the readings result originally from current flow in conductive ore bodies, they are actually related to the effective impedance of the ore body. The Geomag system, therefore, is capable of measuring relative impedance very neatly and quickly, to great depths, and with no requirement for ground contact electrodes, wires or (I externally induced energy. (The term impedance is used instead of resistivity, which implies metallic ohmic resistance. This, of course, is not the case.1 ~... 3

4 Geomag Method -3- March 18th Resistive Strata u Since the readings are related to impedance, the system is not restricted to ore bodies that are electrically conductive. It is only necessary that the sulphide per- centage of the deposit, be of a different impedance than the rock formation. An oil reservoir, for instance, is of dielectric material of very high impedance and resists the flow of telluric currents through it. However, the current that would normally flow through the location of the oil field, is therefore concentrated around the periphry. The situation is, therefore, a reversal of the previous condition with conductive ore bodies, but the results are arrived at by a similar interpretation procedure. The angular distortions (i.e. inclination and declination readings) are much smaller from oil fields than mineral deposits, but measurements nevertheless are made just as quickly and precisely. A vast number of successful surveys attests to the overall accuracy of the system. Differential A refinement of technique in the Geomag measurements involves making a survey at w two different specified times of day. The two sets of readings relate to the morning and the afternoon telluric current differential measurement that is recorded and pro- cessed. This measurement clearly distinguishes between current induced polarization and the earth s magnetic field polarization. Magnetic Influence Magnetically susceptible and polarized ore bodies will obviously also be detected very readily by this system. The survey technique is the same but the results are modified for a more intense magnetic polar character of the ore body. It has been found that the boundaries of a magnetically polarized deposit, show extreme changes in the declination and are thereby more definitely defined. Conductive ore bodies also have well defined edges, but also involve a dipole derived from the telluric current flow, and the magnitude of change is much less. These characteristics are of great value in determining the nature of an ore body with reference to the presence or absence of magnetic material. W Note: The term * conductive as used here, does not imply that the ores referred to are conductors in the sense that metallic copper is a conductor. The requirement is that an ore deposit be more susceptible to current polarization (or is of lower impedance) than the surrounding rock.

5 E. G. s. --.&z?ma~ REPOR T No. 110 Guichon Contact, Mamit Lake, B. C. September 23, TABLE OF CONTENTS - Survey Statistics I General......, Conclusion Resistive Contours l Surface Contours Horizontal & Vertical Profiles ;.y (';~~+ /j. >.("& Cd j" i_,,_ L ' 4 c-4 I'fkd /J' '. &: <?,*,s /cl/. ~; J 2-' - T Department of Miners and,petroleum Resources I t.ko.~ 8% E5ZSSMENT REPORT x..?.&. MAP

6 CI P ELECTRONIC GEOPHYSICAL SURVEYS LIMITED Geomag Geophysical Report #llo on the Guichcn Contact, Mamit Lake, 5. C. GEOPHYSICAL RESEARCH ANO EXPLORAT, N September 23, The Geomag Survey was conducted by our ground crew surveflng along traverse lines set forth by the Contractor George Saarse. A surface footage of 19,0& feet or plan footage of 17,881 feet with the total number of 102 setups and 83 stations are shown in the Plan 110-l of the Resistive Contours, and 110-Z of the Surface Contours, herein enclosed. The xork diotributicn was as follows: 4 man days on survey instruments 4 man days staking 9 man days cutting line 4 man days plotting 1 office day 22 Total Field Days Total: 6 man days interpretation, preparing plans and reports kin Days - The survey was commenced on August 12th, with the field work completed August 29th, l%k.

7 Geomag Report #llo, Guichon Contact, Han&t Lake, E. C September 23, 1961r The surface topography consisted of working largely draw having relatively Under these conditions, pretation compensation of the resistive along a steep slopes to the west as shown on Plan llo-2. the surface contour plan is essential for inter- contours shown in Plan IlO-1. No geological information being available, the interpretation is based strictly upon instrumentation. Relating to the stations on Plan 110-1, the anomalous condition on the south end of the survey extending between the anomaly Al and B2 indicate the rock formations being very close to the surface or out- cropping. These anomalies, when combined with linear anomalies Ll, L2, in Plan 110-2, form a wedge toward station 60. The anomalies Al, B2, are on the outside of the wedge suggesting considerable alteration at this point, It would appear that the linear anomaly Ll may coincide with the foot wall of the low resistance area outlined in anomalies Al, A2, A3 and Ah. If this is the case, the "A" anomalies with the exception of Al, may be the result of the low resistive to the north and east. conclusion The relatively economical geological investigation. areaa at increasing depth shallow coverage of Al, Bl and B2 should permit The strike of A2, A3, and Ah co- incides closely with topographical low of stations 59, 65, 67 and 75 and may have some geological significance. It is recommended that the southern anomalies be investigated geologically in order to further evaluate the causes of the deeper anomalies to the north. ELECTRONIC GEOP

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