Chap. 10] 

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1J50 



ELECTRICAL METHODS 

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803 



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fr 



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teo" 

 w 



v>x\\y//%\vy//9^\v^v/x\vy/Vxswvx^^//»^^^ 



P/afe 



Fig. 10-118. Model experiment on horizontal plate, showing variation of am- 

 plitude and phase of horizontal component across cable (after Friedl). 



By the same technique as that 

 illustrated in Fig. 10-119, numer- 

 ous ore bodies have been located 

 in the Swedish fields, among them 

 being the large gold (arsenic 

 copper) deposit of Boliden. In 

 northern Canada and Newfound- 

 land electromagnetic-inductive 

 methods have likewise been very 

 successful. Fig. 10-120 shows the 

 results of a dual coil ratiometer 

 survey.^"^ Amplitude ratios and 

 phase differences of the vertical 

 field were measured at successive 

 locations 20 meters apart. The 

 position of the conductor is indi- 

 cated by the peaks in the ratio and 

 phase gradient curves. A method 



of calculating the in-phase and quadrature components of the vertical 

 intensity (Zp and Zq) from the phase differences and amplitude ratios 

 is indicated in the calculation form. By combining electromagnetic 



W 30 



Fig. 10-119. Electromagnetic indica- 

 tions on Menstrask Lake, verified by dia- 

 mond drilling (after Sundberg, Lundberg, 

 and Eklund). 



"« H. Hedstrom, A.I.M.E. Tech. Publ. No. 827, 1937. 



