GEOCHEMICAL SURVEY REPORT

ELECXRO-YAGNETIC SURVEY REPORT

THE PAB MINERAL CIAIMS

VERNON M I N I N G DI’IISION, B.C.

8 2 L / l W / \ O d

50- 3 O ‘ d llSo58’1/\/

FOR

EDblAIu3 i’EXCHER OF ENLERB?, B.C.

AND

J.S. A D J G C N OF CALGARY, ALEERTA.

BY

TABLE OF CONTENTS

PilOPERTY .......................................... 1

LOCATION AND ACCESS ................................ 1

GEOLOGY ........................................... 1

S A W L I N G PROCEDURE ................................ 2

ELECPRC-PAGNETIC S U I i v E p ........................... 3

CONCLUSIONS AND R E C O I N D A T I O X S ................... 3

INCLUSIONS

INDEX MAP

GEOCHEMICAL SURVEY FA?

ASSAY RETORTS

STATEMENT OF COSTS

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INT2ODUCTION

I n my 1979 Report on the Peacher Claims I recommended completion

of the Geo-chem Survey in the eastern portion of t h e survey area. T h i s surveg

was completed and the r e s u l t s suggested a l a r g e r claim block be staked t o

cover the possible area of mineralization.

Two claim blocks were staked of 18 u n i t s each over and around the

o r ig ina l f i v e claims. an extended geo-chem survey was done along with an

electro-magnetic survey using a iionka EM 16 Instrument. Some trenching was

a l so undertaken.

PROPERl'Y

The property cons is t s of two claims:- PAE 1 and PAE 4. Eoth claims

have been reduced t o 12 u n i t s each. The west six u n i t s of PAE 4 ( 3WlS t o 3116s )

have been dropped along with the e a s t six u n i t s of PAB 1 ( 3ElS t o 3 ~ 6 s 1. This

report is based on t he 12 remaining u n i t s of PAB 1 and the 12 remaining u n i t s

of PAB 4.

The claims were staked and recorded by:-

PAB 1

PAB 4

-- by J.S. Adamson, of Calgarg, Alberta.

-- by Fdward Peacher, of %derby, B.C.

LOCATION AND ACCESS

The PAE 1 and the PAE 4 Claims a r e located approximately 8 miles

eas t and South of Enderby, E.C. An allweather road i s taken 4 miles eas t and

then 4 miles south, passing over t he Northeast corner of PAB 4.

GEOLCGY

The claims l i e on t he South slopes of t he Shuswap Siver Valley

a t elevations between 1500 and 4500 f e e t , (450 t o 1400 m. ) The area i s

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heavily wooded and covered by t h i ck overburden on t he lower slopes.

Outcrops a r e r a r e and make surface prospecting d i f f i c u l t .

The mineralized area l i es on t he contact between t h e Tertlarg

Volcanics and the Konashee Formation.

The Konashee Formation is made up of low grade Metamorphic

rocks - phy l l i t e s , quar tz i tes , limestones, and intraformational conglo-tss.

The Ter t ia ry cons is t s of volcanics and sediments.

These two rock types suggest t he poss ib i l i t y of contact metasomatic type

and oien type copper occurrences in t h e area.

Good grades of copper were taken from a road cut , and the

geo-chem survey shows a l a rge mineralized extension which unfortunately

is generally covered by overburden.

* GEC-CHEM SAMPLING

An extensive geo-chem survey was completed and sampling was

carr ied out in t h e following manner. The ex is t ing locat ion l i n e running

south to north was extended from the o r i g i n a l 2000 foo t t o 3200 feet . a l l

a reas indicated on Kap #2 werecanpleted a s s h m . Latera l s were run a t

200 f o o t intervals .

The gr id i s located on port ions of PAB 4, u n i t s 1N-46, and lsr-5S:

and PAB 1, u n i t s 1%4S and IELSS.

Samples were taken a t 25 f o o t i n t e rva l s along the l a t e r a l s a s

shown on t he gr id Map #2. A l l samples were taken from t h e 'B' zone a t a

depth of 8 t o 12 inches. (20 t o 30 cm.)

were taken from the clays and gravels a t t he base of t h e peat. A l l samples

were assayed ty Loring Laboratories located in Calgary, Alberta. An 80

mesh was used for a l l samples and t h e assaying was done by hot acid

digestion and atomic absorption spectroscopy.

Samples taken in swampy a reas

-3-

The sampling was done by J.S. Adamson, and K.L. Burns of

Calgary, and Cyril and Jim Peacher of Enderby, B.C. Stnadard geo-chem

bags were used a s supplied by Loring Laboratories L t d of Calgary. A l l

bags were marked and t i e d a t t he sample location. All assays were paid

f o r by J.S. Adamson, K.L. Burns, and Cyril Peacher.

ELECPROYAGNEl'IC SURVEY

The survey was done with a Ronka EN 16 ins t rument by James

Adamson and Kieth Eurns under t he d i rec t ion of t h e author, during t h e

week of t he 14th t o t h e 18th of August 1980. The t ransmi t te r a t SeaUle

was used f o r t h i s VLF instrument,for a l l readings. A l l data was f i l t e r e d

using the D.C. Fraser method. h s c r i p t i v e data i n the enclosed pocket.

The survey was done over t he same gr id a s t h e geo-chem a t 50 foo t

, i n t e rva l s a s shown on Nap $3. The geo-chem survey has been superimposed

on t h i s map t o co r re l a t e t he two surveys.

Trenching was done on the PAB 4 Claim on u n i t 4S1W, and on

t he PAB 1 Claim

used t o d r i l l t he holes f o r blasting. The work was done on the 4,5,and6th

of June, and the 21, 22, and 28 of June 1980, by Cyril and James Peacher of

Enderby, B.C.

on u n i t s 132.5 and 1E3S. An At las Copco Cobra d r i l l was

CONCLUSIONS AND ELECOWJ3EIIXTIONS

The Geo-Chem Survey shows readings up t o 50 times background

norms of 25 ppm f o r copper. The width of mineralization i s up t o 800 f e e t

wide an$ is Jver 3200 f e e t long. The Electromagnetic Survey done on t he

same grid ind ica tes tha t the gee-chem mineralization is l i e i n g t o t h e e a s t

of the deep seated electromagnetic anomally. The overburden covering the

the electromagnetic anomally is much th icker than where the geo-chem

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shouing is located, and a s a r e s u l t

electromagnetic survey anomellies arepxact ical ly no b e t t e r than t h e norms.

The presence of good copper values in the geo-chem mineralized area and

t h e strong electromagnetic reading t o t h e west would seem t o ind ica te the

poss ib i l i t y of a deep seated ore body.

t h e geochem readings over t h e

I would recommend addi t iona l magnetometer readings over t he

electromagnetic anomolons a reas and if t h e results confirm an iron content

I would recommend an exploratory hole be d r i l l e d in to anomally 'B' IJap #3 a t a locat ion t o be determined a f t e r t h e magnetometer survey has been

correlated.

C E R T I F I C A T E

THIS IS TO CERTIFY t h a t I A.D. van der Lee,

- 1. AM a res ident of Calgary, Alberta, and l i v e a t 8212 10th St. S.W.

- - 2. AM a Graduate of t h e University of Calgary, B. Sc. 1971, and have

spent one year i n Graduate Studies i n 1972, a t t he University of Calgary.

3. AM a Member of the Professional h g . Geologists and Geophysicists of

Alberta.

- 4. Have no i n t e r e s t d i r e c t or i nd i r ec t i n the propert ies h o r n a s t h e

' PAB Claims.

5. Pave wri t ten t h i s report on a personal examination of t h e property

and t h e G.S.C. Reports per ta ining t o t h i s area.

A.D. d z - L - van d s r Lee, P. GEOL.

STEEL SURVEIC PIN at S.E. Comer of

\

...... Am: ...... NL.. .Ke.ith..BYz?s .... . . . . ... . P

\ifiQrt b'' ASSAY @F

LORING LABORATORIES

SAMPLE No.

LTD.

% cu

'?Lock C h h s "

Cliff

26CQN-ll5OE

03

* 23

i 3 - Merebe &ertifu THAT THE ABOVE RESULTS ARE THOSE I

ASSAYS MADE BY ME UPON THE HEREIN DESCRIBED SAMPLES. . . .

Rejects Retained one month.

Pulps Retained one month unless specific arrangements made in advance.

Licensed Assaver of Briiiah Columbia

....

.........

TO: . A . & - B . R F s ~ . ~ S . . ~ . ~ ~ .~612..~.lackb~..ILsa.s.~E.~~ '?Ltz+xf..!!Lbe.ea... .. T.2G.2R2 .......

.......................................................

ATTN: Mr. Keith Burns ......................................................................

$ , ifiLQ P be A S S A Y

SAMPLE No.

"Soil Samples"

1 8 o o N - 1 2 2 %

18ooS-1300E

17033 32ooN- 4COE

4253 . 45m

i / ' 47 53

-

Rejects Retained one month.

Pulps Retained one month unless specific arrangements made in advance.

File No. .... 19118.~ ...................

Date may.^ 8, A.9-m ............ Samples . ~-5oil .......................

LORING LABORATORIES LTD.

Page # 2

PPM PPM cu zn

37 45 47 L? 53 39 40 32 49 31 27 32 33 48 50 32 30 57 34 23 28 85 20 31 39 38 30 47

94 81 58 62 64 65 73 82 66 58 60 56 61 68 88

107 - 187' 156 ' 105 ' 158 ~

270 ' 152 1

240 ' 130 '

52 78 83 50

3 Berebg Qertifu THAT THE ABOVE RESULTS ARE THOSE - ASSAYS MADE BY ME UPON THE HEREIN DESCRIBED SAMPLES . , . .

ATTN: M r . Keith Burns ........ . . ........... .. ............. . . . . . . . . . . .... . .. .. . . . . . . . . . . . . . . . . .

$ ,if,iGq P &i' ASSAY

LORINC LABORATORIES LTD.

SAMPLE No.

32ooN- 5m 5253 5 5m 5753 600E 6253 65oE 6753 70% 7253 75oE 7753 w)(3E 8253 85m 8753 9 m 92 53 95aE 97 53

1WoE 1029 l05OE 10753 ll00E 11253 115oE 11753 12m 12253 125OE

Page # 3

m m cu Zn

42 68 47 53 39 54 26 50 21 53 21 40 31 21 21r 17 23 26 23 19 27 20 14 14 19 20 22 11 29 27 2L 5 i 18 12 16

64 70 70 56 52 76 51 53 42 4.4 42 68 16 45 w 46 55

80 87 9i

103 * 26 70 3 perpbg &ertifu THAT THE ABOVE RESULTS ARE THOSE -

ASSAYS MADE BY ME UPON THE HEREIN DESCRIBED SAMPLES . . . .

Rejects Retained one month.

Pulps Retained one month unless specific arrangements made in advance.

- ........... &:&m:.2#!~~&&& Licenaed Assayer of British Columbia

SAMPLE No.

152% 155a 15753 16ooE 16253 165OE 16753 170% 17253 175E 17753 180% 18253 W O E 18753 19OoE

. 19253

.195OE 19753 2 m 20253

Page # 4

PPM PPM cu Zn

78 28 30 65 32 81 27 63 28 61 23 58 23 62 22 62 25 58

94 18

w 63 103 91 81 80 61 90 73 89 67 72 44 82 44 90 63 84 103 76 45 62 44 80 53 83 43 143 93 197 -- 30 180

108 52

37 46 24 97

41 105 - 74 65

3 7pjerobp &ertifu THAT THE ABOVE RESULTS ARE THOSE -. ASSAYS MAOE B Y ME UPON THE HEREIN DESCRIBED SAMPLES . . . .

Rejects Retained one month.

Pulps Retained one month unless specific arrangements made in advance. --

Licensed Asaayer of Britiah Columbia

STATEMENT OF COSTS FOR CLAIMS PA9 1 AND PAB 4 f o r 1980-81.

- PAB 1 PAB 4

Yap No. M82L/7W ?482L/W 60 1 1

Minine Rec. No. 142051E 14 ia

Record No. 814

Claim Owner

PA8 1 ....... J.S. Adamson

PAB 2 ....... Edward Peacher

The above Claims were recorded a t Vernon, B.C. Karch 26 1980.

Geo-chem bags, f lagging and supplies ..............................5 9.5 2

h r i n g Lab. Assays, 6 cu + zn ..................................... 12.90

n I, 90 cu + zn .225.00 II .................................. " 11 11 6 pb ........................................... 9.30 306.72

Geo-chem Sampling

Labour 2 men 2 days 0 96.00 each ................................ .384.0@

%cording 1 man 2 days 3 96.00 ................................. ..192.00

4 X 4 2.days a t 36.00 ........................................... 72.00

Chain Saw 2 days 13 12.50 ......................................... 25.00

Board 2 X 2 20.00 .............................................. 80.00 753.00

Trenchinr:

30 Cu. yds. 6 46.00 ............................................ 1380.00

Gas d r i l l 6 days 2 20.00 ....................................... 120.00

4 X 4 6 days G 36.00 ........................................... 216.00

Chain Saw 6 days (4 12.50 ....................................... 75.00

Board 6 days X 2 X 20.00 ....................................... 240.00 ZO3l.OO

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Electrc-mametic Survey 292 readings

2 men 4 days 0 96.00 ......................................... 768.00

%cording 1 man 2 days a t 96.00 .............................. 192.00

4 X 4 4 days @ 36.00 ......................................... 144.00

Instrument 4 days @ 25.00 ..................................... 100.00

h a r d 4 days X 2 X 20.00 ..................................... 160.00 1364.00

Geologist .. Remrt .......................................... 250.00

2 days on the site &I 200.00 ............................. 400.00 650.00

Trivel 205 of 189.00 ................................... 37.80 37.80

T o t a l costs ......... 5 142.52

"6". .. , -.-- , -

'VLF-EM Data Processing 0. c. FRASER. Chief GeophysicM Geophysical Engineering and Suneys rKeevil Mining Group Limited),

Limited,

~ ~ l s M - - d i ~ a n g l e data or- yield m m p l u ,patterxu which r q u i r e considerable scndy for a pr0op.r interprb tation. A method W a e dereloprd which allows field oper- ,uarS LU transform t he nomamtounble dip anpla into c o n ~ m , m l r l ~ d a a produanp nmductor pattam which are immedim&dy apparent to upLnn t ion paraomel untrained in VLV.~:M interpretation.

c l a c to thr tnn of a condneter. t h e e allowing drill hole6 to b.

yLE'-hM contoured data &"ally peak

i&m'l nccuralely. Hoverer. a dau generally should noc bt rr.4 dune. to select drill -&gels b e c a w strueturc) ma, ha mftiuently conduc t i~c to yield s M n s anomalia. m..r muenetie and/or rertiad-looo EDI corrsht io~ mar

tn;[Gnnaonta. For c~ample , t!m Rntlgouche orebody in the Bpthumc camp.of Il.r Bromrriek yielded a VLF-EX anomnlr as dutrnct xs that om,Lund by IP. although the w- Jd not r a m n d to rcrftzal- or horimntal-lmo EM.

...

field personnel, and simply involves additions and aub- tractions. Both magnetic and VLF-EX data can be collected

bp a single individilabar parl of a m u n d evaluation program. The VL.F-EX method can pmvida contour maw which ma7 be as useful to expioration geologists 8s magnetic maps. The key to the usafulnoss,. how- enr. lies in the data processing. b e n u s e raw dip angie data frequently are more confusing than eluci- dating. This point is illustratad in Figra-u I, which presents d igang le data fmm the Tamagami mine in Ontario. Clearly, the complex pattern r equ i r a some tborght for proper interpretation. Conversely. Fig- ure 3 provides a conductor pattern -hi& is immediat- ely apparent eFen to those untrained in VLF-EM in- tcrpntation. It is obtained from the dah of Figwe I, using the method described in the Appendir The con- toured units ore exprused in degreu. Only the posi- tive quantities are contoured.

A ~ ~ ~ 1 1 0 0 XAS BEEX D-9 ( F A e r . 1969) which .I

ennblk somewhat noisr, noncontorrrable dip-angie data to be transformed ~ILW l e s noisy, contourable data. T h i s data pmetssing .3 performed routinely by . . . --

IU *I=

D. C. F R A S E R obtained a Bachelor's and s J h t e r ' s degree in p+ologg a t the Unilmsity of New Brunmick and, in 3 6 6 , a PhS. degree in gr?e physics Y the University of Califor- nia at k k e i a y . He h u performed m a m i nn induced polarization. re- sisti%+tp- magneti~, gravity and electrouzugaetia, induding the design of new mterpretatipn metho& em- ploying. m part, dimtal fitering and cornla-* techniques. F&cently. he has kuE .inrolved to a considerable

C x b n t jn mapping conductivfzf inhomogeneitin, Srst e t h gfcund equipment as a problem, and ?hen *th arbnrna equipment in eoUzvwration with Bamnger Re-

FIGURE 1 -,Diq-rngle --EX data in the ,ricinitp d the Temagami mine. The arrow dc f tnn the pnmrry field direction from the trdnamitter at Seattle, W d i n g t o n (after Fmser. 1969).

&Ah Limited. 3r. Fnuer has worked ?u several petroleum and min-

ing comprnies and currenL? b chief gcoph?sidst of Geo phyaicnl Engineering + so173p. Limited, a member of the society of E+oratron II&ophys$tts and of the CIX,

Y nut ora lden t of t h Canadian b l o r a t i o n Geo-

.$Yp ,(,( . . a 04

FIGURE 2 - Contoured YLF-EX datz, in dew-, M calculated from the map of.Figure 1 (after Fmmer. 19691.

i . .. . .

. , ~ : ~. -. .- - .. . ~. .

-. . . i ' L ... loop corklation also coincides with a magnetic ano- ' ' maly, and probably is due to magnetic sulphides. It .. .

FIELD EX4JIPLES ' -. -

The foilowing field examples were & s e n to illus- trate the three primary uses to whi&.VLF-EX h u been aixplied by Geophysical Engineering and Surveys Limited. .

T2tere.iie c e ~ h i enviroiments wh& VLF-EX': General Prospecting. .

General prospecting or g m m d evaluation Prodd" ern be used as an aitunatc to IP. Thore - the a- the most common USE for VLF-EX Ground often m '.. vironment. &mcteriz& by m i v e o r ha*& disse- obtained which Only gcnaral to minated suiphidu which occur within 300 feet of surr exploratbn, as Then there is insuffiti-t g d o d d face and yet do not respond to convcntionpl E X zp information repording the specific b X e t sought In w w considered to b. the ma$ suitable geophysical such Ow. m @ e t i C and method for the detection of such bodies (Hallof, 1967). tinely performed without the guidance of a zmhys i - ' Howe\-er, it is wcll worth M n g in these cist. VLF-EN condueton Ua tested by Short trawrs- es with vertical-loop EM. The anomaly paems Zen- savings tbat result if the method t ruponoivL suhsbntial XS eost an envimnments because 02 the v u y

erally are s u f f i d d y dear 90 that a P P b P * bench- -1% Figuzr 6 i l l r r e b a --EM O V ~ . ing, driying o r abandonment wiU k decided without the ~ e s t i p o u h ~ omw7 in the the area ,,f N- c o m u l ~ g a mh.pSi&+ b P t i 0 - occur

. .. Bmrmick. Figure 5, showing IP ehargrabiHtJr con- pat tern become complex. '.. tours, allows a comparison to be made of the relative Figure 3 i l l u m a t u a survey in which tsro strong merits of IP and W - E X for this tppe of m i n d -

TLiLF-E3I conductors wen obtained. The sourhem ano- ization. The Restigouche body did not respond to vw- maly has vert id- lwp EX correlation and the north- tical- or horhntal-loop EX beeause of the hi& wha-

are

-- ___. . "ULS' S Y ~ , ~ " I I , I I S I , " u-...,=- ... *_._..". ,---.I - -- -_ ~. ~

'\\.auld not be as amenable to the use of VLF-EX in . w' 1

i.e.. for general prospecting. mopping of-structures and as a judicious alternote to IP, form our primary , ' $lace .of IP. 2 truly disseminated

C 0 t p m v j d e b - w * w e y T h d , applicitions of n F - E x to prnperty eraluation. errect. as n-as found to be the case or e brecua .

APPENDIX e e Tribog mine near Batchmana, Ontario.

Interpretation The Data-Processing Technique

prosimatelp 20.000 hz severely limits the depth of ' ..

exploration in areas of conductivm overburden. As 5 e-le, penetration of_tbs-lO&.to-20(Liee-, FIGURE 'I-ESample of the data pra-ing dolat ip- in Illustrating that the contoured qpmtltles arc ohtamed

--- mmms area _____.- often is not -- achieved. simply from addition+ and subtractions p e r f o n d on the

tional conductiritg,. such as the Bathunf-ar-depth . A 50-foot interppl is to avoid o f~q&-At iod -gen~Uy is limited to about 300-feeL This depth xr?i predicted ~m modd curves in F~~~ the problem of near-surface condueton amenring as

deeper conductors. as could occur if tbe station spac- WW, and 2pp-n t o ~ b e true in practicc = o w the. inp -. larger. In ed Dractieo d a b ars eoIlfftrd. ... ':- at 100-foot intei la l , with -foot readings being talc- hestigouche deposit (F igwe 0. .~,-~eri where anomaliu Later. 50-twt arti-

. ' L, ,,-, . '

In - regionrrheze the -.. o w r b u r d e ~ - a - l s s . excep- dip and-.

. - . .

.. - .. .. -i,c -

.-=.; ~ ....... f&l. data are 'interpolated in man-anomalons arm .. .... . __ . . . . . arior ta nuformian the calculations. This Rmadure

CONCLTJDCU'G REiMtLRKs .... - ..... __-_ ~. _..~~ ...,

VLF-ZJI sulseys are exceptionally easy to perform.:.' avoids soma confuGon in the contour pat& which but the dip-angie data may be exceedinglr Cf i cu l t ,would. result from nesr-surface 'geological noise'. to interpret correctly. This latter point has pmduced ~

unfarourable C O ~ e n ~ regarding the Utilit)- of T v - . ~ because the negative q u a t i t i e genera!& E p m e n t EX as a prospecring tool. The data-Pmceasinz method . ano& a&. Cowqurntty, the inclusion of nega- used to transform somewhat. noisy, noneontourable . tive contom \\.ou]d Serve only to confuse the condue- dip angles into less noiw, contourable data grcatb . to r paern Howepy, if a backward crossover w e increases the ralu of surveys. . ..-~.: produced by a geological source, an erroneous inter- ;_The efficiency =+--==? of data flo% is significantlr in- pretation of the contour map and the dipPngle pro-

sormally, onl,. thi-positjve due are

company per- ' files would. result. To date, Such a crossover has not This is b e been recognized on the predominantly in-phase d i g

projects. rather - than requiring a geophysicist to study each dipangle REFERENCES

~

Fraser, D. C., (1969). Contouring of n F - Z X Dau; Ge- physiW, VoL 34: pp. 958967.

Hallof. P. G., (1961) . The Use of Induced Polarization bfcuurrment3 to M:pu!ve Su'phide 'lineralin- tion in Environments IU phxh EX Slethuds Fail; paper presented a t Cansdran C e n t e n d Conference on Mining and Groundwater Geophpiq Xiagara,

map. Contoured '/ZF-EX maps f o F a,dseful complement

to m a p t i c maps. The survey anddata-processing cost is similar to that for a hand-held fluxgate magneto- .. meter. -

For general e ~ ~ l o n t i o n in the Shirld, VLF-EX con- ductors generally should be tested with. vertical-loop :. E31 to separate massive sulphides (and graphitej from - *me k h n i q u e i3 rnalopou~ to passing the dip-angle && conductire structures. As such Structures can be through a bandpass filter which (1) completcip remom mapped with VLF-EN. this provides mother use for DC bias and m d y attenuates long \=ye Ln&s. (2) the Further, masive oI,d heavily disse- completely remore Nyquist fnwencr no=% (3) P& shifts all frequencies by 90 dezrecs and (4) has thr minatd sulpbidri. which do not respond to conwn- bandpnsa center& at a \vavc length of f i ~ t i m e the tional EX. wili yield VLF-EM anomalies as distincy; sation gpa~ing. .::-. . .

13

. . . . . .~

.. . . .

- . .~ .

.. .. ~. . . .~ .. ..~ ~ . .

~. . . , . . . ~ . ~ . .- . .~ .. . . ~~ . . . . . -.- . . -. ... . . ~- .. . .. ' .- - , . . -

. - . . . . . . . ..

CONTOURING OF VLF-EM DATAt

D. C. F R A S E R .

R o s p t c h g for coaducdr; dcpodts with ground VLF-EX instnrmcne hu received con- sidwble impetus with the rcamc development of lightweight receivers. The M e geologic noise componmt, whichraulbfmmtherehrivelyhigh- M t t c d frrqumcy, has ~ e v d some aitio to avoid use of the tcchniqw n e e aho roucindy perform surveys with a VLF-DI unit 6nd that, in SOIUC areas, a 5-degna p d - t ~ - p & anomaly QP be sigdcant, whcrear ~ooda baving smplitnda in cxces of 100 degrees may xcur, as a& Conscquucntly, there is L dpamic range problem w b m pramring the rada as pro6Ia

plotted oa a &Id map h data manipuktion- procedurr ii d a s i b a i

which &oms noisy nonmtourabie data into lar noby mutourable data, thereby diminalinq the dynamic range problem and Rdudng the noise problem. The manipulation is the muit ai the appLicadon of a dScrence -tor to mns form z a d u g r into peaks, and a low-pyj smmthing operator to reduce no& Expaientc hu shown that Bdd penonnd can routinely perform the calculatiolcl which simply inwirc additions and subtractionr

LyTIonucnm VLF-EX datr can be esceedbgiy diF6cnlt ta

interpret beuusealvgcgeolo~cnoisecomponsrt can rault fmm the rdativdy high-aammittcd kcquency of about 20,ooO Hr Routine surveys can *dd udas data dsr +.aI care is taken both in survey proccdrve and in daka prsartz- tioa The purpoae of this paper L to d d e the

swcg procedure and the mericd oi data praen- tation in use by the KecviL-Sining Gmup and to illusuate the advantags of t bs approach.

tivc - water. Skin depth is apprordmadr 3 . 6 4 ' meten, rhuc P is the raknvity 01 .I

homogeneous haifspace in-ohm-at, %the s u m p tion that the frequency is 20,GfM Hr s d that ihu

hallp.cc ir magncticslly nonplarizable. Come- qumtly, depth of cxpiontionir sevady restricted for ovcrburdm ruistivities les than 200 ohm-m.

strce the area to be p r c a p e c € c d n o d ~ s of comiderablc dlrancc from the transmitter sta- tions, the primacy Bdd ir uniform in the yea. alIowing rather simple mathehemptics to be used in

anomaly predictiouand analysk.

962 F n v r

I I '1 OI '1 z1 -'I allows D mothemhtid modd of D dike tn be mnsuuacd becaw the 6dd from aline source k ISOWU.

where k is a positive consat having rhe dimen- sion of length and is dated to the Urnductivir?. and dimensions of the dike, and vhue Ho ii the

j < Forbrrrip,onlyadikcwhichLLvgeindepth primary VLF-EN strength at the dike. The !

i i

: ertmt and in length w i l l be conddacd herein. measured dip an& k

triiuce to the mcuured dip and- because the

The horizontal as. and vertical Zls, second-

only the top Line s o m e of Figure 5a dl con-

o t h a cursent line SOUM are very far away.

6dds ue (Ewe 5b)

a = tan-L[ j =*.

-J

Lz + 31 + 21 3. Hs, +- H 1

1 $

i

3 k* = tan-'

z Hs. kEo-

3 1 + 272 Ifodd dip profiles cu be computed for various

.As a meurs of tating the effect of the filter 4 operator, a single k value was chosen to yield t !

depths L only by assuming a value fork. I

Hs, = kEo- x: + *l'

j ! i

R E J E C T

6 i C 2. a m C

0

t

965 bntoudng VLF-EM Data

DlUE 2 . 100’ .So’ ‘\,_---

‘IG. 6. Dipang!c (dtrhed) and @ercd (solid) m a for modd d5c and sphm for wed depths oi b-I, w h m i u depth to top of dike snd to center of rphcrr.

t

966 Fn

data station interval, and will lii a deeper conductors. This "geoloeic noise" wlu somewhat confuse the contoured output Cenually, a comparison of the 50-it data station dip angle pro6la with the contoured filtered OuQut sufficu to i n d i a e approximate depth to source and to allow recognition of MWCU deeper than 3M) f t As an rddc, same geophysicists have claimed

that a rusonablc dike mcdd depth estimate can be obtained directly as half tbc distance between dip angle p&, because the v a t i d fidd Hz, perl;r at s-zz. Hon,wer, this formula is not appliable to dipangle data, as be YCD by the dike awa of Egure 6. For this example, thc formula provides erroneous depth atimatm of l50,200,3lS, Us, and 62.5 for true depths of 50, 100,200,300, a i d 500 fL

The s p h d A m d u a i n g sphere in a VLF-EM fidd dl

produce an anomaly to equatiau in Ward (1967). Far a travasc directly over a sphere having ik center at depth z, and run in the direction of the primary fidd Ho, the anomaly is,

(2s' - .J) (9 + ,*)"a

Es, - kHe

-&ere k is a pcsitive constant which uhusta at P/2 , where R is the sphere radius, and where quadrature is ignored. The m d dip angle as a function of station loation r is (where r is m dirrnly o v a the sphere center),

a=tan-( Hs. Es. + Ho )

X o d d dip profiles ~ 1 1 be computed for various depths I only by assuming a vduc for k. The sphere.cnn*a of Figure 6 w m c a saturated b- value for a sphere radius of 50 f: Obviously, a sphere baving its center at a depth of nuta than trice its radius g m d y wi l l not be detect- rblr Hmm-er, the filta opentor aids h the ~ecognitim oi a spherical conductor because it ampries the anomaly, for the small s p h e SLcs

IYT

Usually encountered in nature, assuming data spacing is 50 fi

TOPOGI*PKIC P.EU

Whittla (1969) -fly d k b e d a top- graphic ded which may arise when suunqing with VLF-EM in mountainous regions. The rprdd wavdmgtbr which result from the phe- nomenon he d u u i b a arc n a t l y attcnuted by the filter and generally do not a p p u r on the con- b u d maps. Whittla a d v w t o the w of fin< daivativa to remove the topographic Caccr ne 6lW opmror dacribed h a u n uses rhe fist diilatnce (i.c., the mht duivative) a one of ik companmtt.

MDITKONAL A?PLTUTTONS

The simpti+ of the ulaalations aUovs pracri- ui appiiution of the6lter to any form of ground. geophysical data which yidds zuwosdngs over t n ~ e t s . such as v d d loop EX and . U m q Howver, i t is di5arlt to justify the ysc of rhc filter on v a t i d loop EX data because nother dynamic nnge of anormlia nor geologic noke is l u g r In Afmag, utilization of the filter is noi rcwmmcnded b e u s e of the vaxying direction oi the primup. 6dd.

Airborne VLF-EM systems, which mcvurc panmetas yidding zcrocrossing over tugcis. arc bdng markermi. If the data were collected on magnetic tape, a computer could be used to appiy the filter, thereby allowing contouring of the dati However, in this situation mare saphisti- cated 6lta operators shouid be employed.

If the filter is to be applied to data o tba than . m d W - E M , the sample inrcrvd should 'Jc sdected to QISUIC that the p s b a n d of the filter is comctrdative to the frequency components oi the a n o d e s Mughi

A consideration of gcolo& note and conductor shapa illustrates that VZF-EIf data should be collected at 5 0 4 intervals, and that tbe de. scribed Qto operator should be employed. T h e filtered d a y Then contoured, provides a dau pmentatian which s i m p l i h intqrctation. T h e filter a h a m p M a anomalia from near-surizcc, highly conductjug ore pads which is an important feonrrc in m e r a l mining d i s ~ c t s such as 11

Tribag and Tcmagami, both in Ontario, and in Louvicourt Township of Quebec