We see clearly th at applying the new proposals in the ISIPS to calculate the ap parent resistivity and polarization values perm its defining research objects in more detail and locatin
Trang 1VNU JOURNAL OF SCIENCE, M athem atics - Physics T XVIII, Nq4 - 2002
T H E A D V A N T A G E S O F T H E N E W P R O P O S A L S
I N T H E I M P R O V E D S Y M M E T R I C I N D U C E D
P O L A R I Z A T I O N S O U N D I N G M E T H O D
Vu D u e M in h
C o lle g e o f S c ie n c e, V N U
A b s t r a c t T h e higher resolution, greater investigating depth, increasing reliability of ge ology forecasting results and possibility of expanding the application o f the improved symmetric induced polarization sounding m ethod have been illustrated by theoretical and field medium are th e advantages of the new proposals presented in this article.
I I n t r o d u c t io n
III th e a rtic le [2], th e ou r n ew p ro p o sa ls, e s p e c ia lly th e P e tr o v sk i in d u c ed p o la r
iz a tio n (IP ) p a ra m eter r/p, h a v e b e en in tro d u ced for d a ta p r o c e s s in g in th e in d u ced p o
la riza tio n so u n d in g m eth o d ; a s a resu lt, th eir a d v a n ta g e s in c o m p a r iso n to th e p r ev io u s
co n v en tio n a l p a ra m e ters h ave b e e n illu str a te d by c a lc u la tin g for th e th e o r e tic a l m ed iu m
H ow ever, th e P etro v sk i tra n sfo rm in g form ula c o n ta in s d e r iv a tio n w h ich is n o t s ta b le , so
d esired re su lts are not a lw a y s o b ta in e d W ith p u r p o se to o v erc o m e th e s e d isa d v a n ta g e s,
w e have p ro p o sed t h e im proved s y m m e tr ic ele c tr o d e array an d th e c o rr esp o n d in g m e a su re
m en t p roced u re, th e sim p le a lg eb r a ic tra n sfo r m a tio n s (w ith o u t th e d eriv a tio n ) t o a p p ly
to th e r e sistiv e ly so u n d in g m e th o d [ l] T h o se im p ro v ed s y m m e tr ic e le c tr o d e array an d tra n sfo rm a tio n s are o f scie n tific arid p r a ctic a l sig n ifica n c e B a s in g o n th o s e research es, w e
a lso have p ro p o sed th e im p ro v ed sy m m e tr ic IP s o u n d in g m e th o d (I S I P S ) a n d it h a s b een
te s te d e ffe ctiv ely a s th e a rtic le [3].
In th is a r tic le , w e w ill illu s tr a te th e co rr ectn ess a n d a d v a n ta g e s o f th e n ew p r o p o sa ls
in th e IS IP S by th eo re tica l a n d p ra ctica l m ed iu m ; p r o p o sin g p o s s ib ility o f e x p a n d in g and ach ieve b e tte r g eo lo g ica l e ffectiv e o f th e n ew p ro p o sa ls t o th e a p p lic a tio n o f th e IS IP S in fact for d a ta p ro cessin g o b ta in e d b y u sin g th e p rev io u s c o n v e n tio n a l IP so u n d in g m e th o d
I I B a sic s o f t h e n ew p r o p o s a ls in t h e im p ro v e d s y m m e t r i c in d u c e d p o la r iz a tio n
s o u n d in g m e th o d
I I 1 T h e n e w in d u c e d p o la r iz a tio n p a r a m e te r s
A s know n , t h e apparent p o la r iz a tio n is c a lc u la te d by th e fo llo w in g form ula:
w here p ị a n d pk are th e a p p a ren t r e s is tiv itie s o f th e p o la r ized a n d n o n - p o la rized m ed iu m , resp ectiv ely , co rr esp o n d in g t o th e r e s is tiv ity p a ra m eters p i a n d Pi w h ich are r e la te d by: p* = P i / ( I — r/i) w h ere i is th e m e d iu m m o d e l in d ex
T y p e s e t by
13
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B a sin g o n th e a b o v e d e fin itio n s, w e h a v e a lso d efin ite th e n e w I P p a r a m e te r s [2] sim ilarly:
- T h e p o la r iz a tio n o f th e sy m m e tr ic In d u ce d P o la riz a tio n s o u n d in g m eth od : rj9.
- T h e p o la r iz a tio n o f th e (lip o le-a x is In d u ce d P o la riza tio n so u n d in g m eth od : r)r
- T h e P e tr o v sk i p o la riza tio n : Tjp
A c co rd in g t o [3], th e im p ro v ed sy m m e tr ic In d u ce d P o la riza tio n so u n d in g e le c tr o d e array is a llo c a te d a s th e fo llo w in g :
— - • - • ♦ -♦ - • -•
-w h ere, -w ith o n e c u r r e n t-e le c tr o d e se p a r a tio n A B , from th e m e a su re m en t -w e m ay o b ta in
Psi(r i)> Vsi(r \) a n d Ps2(r2)> Vs2(r2), co rr e sp o n d in g to rj an d r 2 In su ch a w ay 4 curve
P i\ , Pi2 a n d TỊS\ , ri„ 2 a re o b ta in e d
T h en :
where psr - the dipole-axis resistively sounding curve obtained by transform ing from th(!
s y m m e tric re s istiv e ly s o u n d in g c u rv e p a.
T h e v a lu e s o f P e tr o v sk i r e s is tiv e ly so u n d in g cu rv e ppar are c a lc u la te d by th e fo llo w
in g form ula:
T h e n a ll th e n ecessa ry in fo r m a tio n w ill b e c a lc u la te d acco rd in g to th e s c h e m a show n
o n figure 1.
Figure 1. S ch em a c a lcu la tin g p a ra m eter s by u sin g IS IP S array
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I I I C h e c k in g t h e m u tu a l p r in c ip le
W e have m ea su red a n d c a lc u la te d ex p e r im e n ta lly th e m u tu a l p r in c ip le o n th e field
m ed iïiu n B elow w e p resen t o n ly th e e x a m p le r esu lt in T an D a n - H o a n h B o - Q u a n g N in h
F ig u re 2 sh o w s the a p p a ren t r e sistiv e ly cu rv es prstr (ro rstr) p r a c tic a lly m ea su red by
t h e im p r o v e d sy m m etric so u n d in g array M A B N , Prsng (ro rsn g ) p r a c tic a lly m ea su red by th e
im p r o v e d s y m m e tr ic so u n d in g array A M N B an d th e co r r e sp o n d in g P etr o v sk i re sistiv e ly
s o u n d in g curves.
F ig u re 3 sh o w s th e P etro v sk i re sistiv e ly cu rv es ỌyrstT (ro p rstr) for array M A B N an d
Pprsng (rop rsn g) for array A M N B ; th e P etr o v sk i r e sistiv e ly cu rv es Pprsxd (ro p rsx d ) d erived
fr o m th e tra n sfo rm a tio n o f th e v a lu es Pr p ra c tic a lly m e a su re d by th e ID A I P S array an d
ơ n e v a lu e Prjxd(r max) m easu red by th e eq u a to ria l d ip o le array a t fin a l siz e p max o f th e
I D A I P S array.
— r o r s *
— ro rs rç j
; ; Î i — ro p r s tr
; - i - i — f c p r e n g
10*1 - — * - — - *• - — -— - ~.-iU
Figure 2 C urves p rstr (rorstr), p rsng (rorsng)
a n d co rresp o n d in g Petrovski curves
W e r ea lize th a t curves are fitte d T h is p roves t h a t th e m u tu a l p r in c ip le is righ t for
a ll th e a rra y s, th e ele c tr o d e sp a cin g , th e m e a su r em en ts a s w ell a s th e tr a n sfo r m a tio n s th a t
h a v e b e e n u sed to con firm th e m e th o d
IV C o n f ir m in g t h e c o r r e c tn e s s a n d a d v a n ta g e s o f t h e n e w p r o p o s a ls
I V 1 Calculating values o f the polarization sound ing curves
★ The threc-laycred g CO-electrical model
B y s im u la tio n m e th o d in P C , w e h ave b u ilt th e p ro g ra m s o f calfcu latin g th e p o la r
iz a tio n s o u n d in g cu rv es o n layered g e o e le c t r ic a l m o d e ls for d ifferen t e le c tr o d e array by
M a tla b la n g u a g e W o o n ly g ive a sp e cific ex a m p le o f th e th r e e -la y e r e d g e o -e le c tr ic a l m o d e l
as fo llo w in g : pi = [14.51]; TỊi = [241); h x = [15]; w ith i = 1 , 2 , 3
F ig u r e 4 sh o w s th e th e o r e tic a l ID A IP S curve Tịr (e ta r ) a n d th e cu r v e co rresp o n d in g
to th e I D A I P S cu rv es 7]sr (eta sr) o b ta in e d by tra n sfo rm a tio n
Trang 4F ig u re 5 sh ow s th e th e o retic a l P etro v sk i cu rve T)p (eta p ) a n d th e Petrovski c u r v e
vpsr (eta p sr) o b ta in e d by tra n sfo rm a tio n
F igure 4. T h e th e o r e tic a l c u r v e rjr (eta r) a n d Figure 5. T he th eoretical curve 7]p (etap)
c u r v e ĨỊsr (e ta s r ) o b ta in e d by t r a n s fo r m a tio n and (etapsr) obtained by transformation
★ The field m edium
T h e te s tin g c a lc u la tio n s h a v e b een p erfo rm ed in T an D a n - H o a n h B o - Q uang N in h
an d D a k so n g - G ia Lai B elow w e o n ly p resen t th e ex a m p le cu rv es m e a su r ed a t p oin t 22
o f th e profile S l l in D ak so n g - G ia L ai
F ig u re 6 show s c u rv e 7]r (e ta r) p ra c tic a lly m e asu re d by th e ID A IP S array ; th e
ID A IP S cu rves 7]sr (eta sr) an d r]p3r (eta p sr ) o b ta in ed by tra n sfo rm a tio n o f carves p8) TỊa
p ra ctica lly m ea su red by th e IS IP S array a n d par.
F igure 6. T h e p r a c tic a l c u r v e 7]r (e ta r ) a n d
c u r v e 7/irx(e ta s r ), 7J (e ta p s r ) o b ta in e d by tr a n s fo r m a tio n
In co m p a rin g , p r a c tic a l m ea su red cu rv es an d corresp on d in g cu rv es o b ta in ed by tra n sfo rm a tio n are n early fitte d , o n ly th e v a lu es a t so m e final sizes is n o t th e sam e T h is proves th e co rrectn ess o f th e a lg eb ra ic tra n sfo rm a tio n s m en tio n ed a b o v e B esid es, P etro- vski curve a lso h a s reflected clea rly reso lu tio n a b ility - th a t is it s a d v a n ta g es.
I V 2 P r o c e ss in g d a ta o n th e p ro file
T h e n ew p ro p o sa ls h a v e b e e n a p p lied in tw o directions:
1 P ro c essin g and a n a ly z in g d a ta o b ta in e d p rev io u sly b y th e n o rm a l IP sou nd in g
Trang 5T h e a d v a n t a g e s o f t h e n e w p r o p o s a l s i n t h e i m p r o v e d s y m m e t r i c 17
m e th o d in order t o e x p lo it and ad d o th er u sefu l in fo rm a tio n in tw o w ays:
4- In te r p o la tin g values o f cu rv es TỊk an d pk o b ta in e d p rev io u sly by the n orm al IP
so u n d in g m e th o d to v a lu es o f th e im p ro v ed IP cu rves w ith th e co rresp o n d in g sizes o f electro d e sp a cin g a n d co efficien ts.
-f Prom th e s iz e s o f n o rm a l ele c tr o d e array, c a lc u la tin g co rresp o n d in g coefficien ts
o f th e im proved e le c tr o d e array.
2 P r o c e ssin g a n d a n a ly z in g d a ta o b ta in e d by th e IS IP S m eth o d
B elow w e p r e se n t o n ly th e resu lts o f a p p ly in g th e new p ro p o sa ls to ex p lo it d a ta
ob ta in ed p rev io u sly b y th e n o rm a l S IP S m e th o d on profile 20 in S o n g G ia n g - Q u a n g
N am , w hich w ere m ea su red by U n io n o f P h y sic -G e o lo g y in 1999.
★ The results o f processing and analyzing data obtained previously by the norm al
S IP S m ethod on profile 20 (se e figu res 7, 8)
• L ine 20 w a s form ed in th e N o r th e a st - S o u th w est d ir e ctio n p erp en d icu la rly to the folding stru ctu re w ith N o rth w e st - S o u th e a st d irectio n in th e S o u th e a st o f G ia n g R iver.
Figure 7 Contour section Tị on th e profile 20 (%)
(S o u rc e : U n io n o f P h y s ic -G e o lo g y )
• A lo n g th e p rofile, th e fo llo w in g m a in g eo lo g ica l fo rm a tio n s are identified:
-f B en g ia n g - Q u e so n m a g m a co m p lex :
G E O L O G I C A L S E C T I O N
Figure 8 : Geological section of th e profile 20 ( S o u r c e : U n io n o f P h y s ic -G e o lo g y )
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M ain co m p o n en ts: g ra n o d io rite, b io tite h orn b len d e, a n d to r a n ite b io t.te h o r n
b lende S p ecific p h y sica l fea tu res are r e sistiv ity w ith p = 2, 000 — 3 ,0 0 0 oh m s.m p o
la riza tio n 7/fc = 3 — 5%
D irectio n s:
1 G ra n o d io rite o f B e n G ia n g - Q u e so n co m p lex , p h a se 2;
2 S ch ist o f K h am d u e fo rm a tio n , layer 3;
3 S ch ist o f K h a m D u e fo rm ation , layer 2;
4- A ltered zones;
5 Faults;
6 V en ts o f gold -su lfu ric q uartz.
+ T h e m etarn orp h ic sed im en ta ry rock s o f K h am D u e fo rm a tio n co n sist of:
- U p p er layer: b io tite - g ra n ite q u artz sh ale, m ic a q u artz, a n d p la g io ela se - bi-
otite quartz Specific physical features are resistivity w ith p = 1,000 — 2,000 ohms.m,
p o la riza tio n w ith T]k = 2 — 4%.
- Lower layer: B im ica g n eis, b im ica q u artz, b io tite g n eis, sc h is t, a n d b io tite q u a rtz
S p ecific p h y sica l fea tu res are r e sistiv ity w ith p = 500 - 1 ,0 0 0 o h m s.m , stim u la te d p o la r
iz a tio n w ith 7]k = 2 — 4%.
M eta m o rp h ic sed im en ta ry fo rm a tio n s w ere str o n g ly fo ld ed a n d d ivid ed by d eep
fa u lts p erp en d icu la r ly w ith th e su rv ey ed profile A lo n g th e fa u lts, rock s are stro n g ly
d e stro y ed a n d in filtra te d by su lfu ric ores D estro y ed zone h a s sm all re s is tiv ity p = 2 0 0 —500
o h m s.m an d high p o la riz a tio n T]k = 3 — 5%.
G old b ea rin g p o ly m e ta l su rp h id e - q uartz z o n e s h a v e th e r e s is tiv ity relev a n t to altered zo n es an d high p o la r iza tio n rjk = 5 — 10%.
• T h e aim o f th e IP so m id in g m e th o d is to so lv e th e fo llo w in g tasks:
+ T o s tu d y folded str u c tu r e s alon g th e su rveyed profile;
4- T o d efin e gold b ea rin g su rp h id e - q u artz zon es.
★ The results o f applying the new proposals to exploit data
W ith a p p ly in g th e n ew p ro p o sa ls to e x p lo it d a ta o b ta in e d p r ev io u sly by th e norm al
S IP S m e th o d o n profile 20 in S o n g G ia n g - Q u a n g N a m th en co n to u r se c tio n s o f p o la r
iz a tio n h ave b een c a lcu la ted and rep orted B elow w e o n ly present, th e ex a m p le c o n to iư
s e c tio n s T)sr an d Tjpsr o n figures 9, 10.
F igure 9. C o n to u r s e c tio n 7]sr (%)
Trang 7T h e a d v a n t a g e s o f t h e n e w p r o p o s a l s i n t h e i m p r o v e d s y m m e t r i c 19
Figure 10 Contour section 77 pnxd (%)
The results of applying the new proposals in the ISIPS to exploit d a ta obtained on
p rofile 20 in S o n g G ia n g - Q u a n g N a m can b e seen th a t:
-f Detail division of geological com ponents in the section;
- M a g m a tic g ra n o d io r ite fo rm a tio n is ch a racterized by r e s is tiv ity 2,0 0 0 - 3,000
o h m s.m , p o la r iz a tio n 4 - 5%;
- M e ta m o rp h ic se d im en ta ry rock s o f K h a m D u e fo rm a tio n s are ch aracterized by
r e sistiv ity 1,000 - '2,000 o h m s.m , p o la r iza tio n 3 - 5%.
+ T h e b rok en zone, d e s t n ic t e d a lo n g th e fa u lts is d e a r ly d efin ed T h is zo n e is
ch a ra cterized by low r e sistiv ity ‘200 - 800 o h m s.m , p o la riz a tio n 6 - 8%; d efin in g in m ore
d e ta il th e g o ld b e a rin g sur phi d e - q u artz zo n es w ith th e p o la r iz a tio n from 8 to 10%
T h e contour s e c tio n TỊpsr, sev era lly , d efin ed clearly and in d e ta il th e v e n t b o d ie s w ith the
polarization from 8 to 10%.
We see clearly th at applying the new proposals in the ISIPS to calculate the ap
parent resistivity and polarization values perm its defining research objects in more detail and locating m ore clearly.
V C o n c l u s i o n s
1 For th e first tim e, th e P etr o v sk i IP p a ra m eters (e sp e c ia lly r/p) h a v e b een p r o
p o sed and th e ir scien tifica lly th e o r e tic a l b a se b u ilt an d a d v a n ta g es th a t th e y e x h ib it higher
re so lu tio n a n d g r e a te r in v e s tig a tin g d e p th th a n th e c o n v en tio n al p a ra m e te rs pk i Vk have been confirmed by us.
ã
2. T h e n ew p ro p o sa ls in th e IS IP S h a v e h ig h scien tific relia n ce , rea lly u sefuln ess,
and scientific and practical significance T hey elim inated the fundam ental disadvantage
th a t the transform ation betw een curves through the unstable derivation existed for a long time One of the advantages of our proposal is only using the simple and reliable algebraic form ulas to transform curves C reating algorithm s of processing and analyzing the d ata using the new proposals in the ISIPS basing on selecting reliable information
w ith comprehensiveness T hey also have m ade the geology forecasting results clearer and
Trang 820 V u D u c M i n h
m ore reliable, reflected th e n early real IP effect o f s tu d y o b je c ts, in cr e a se d reso lu tio n o f
w eak a n o m a lies A ll o f th o se h a v e illu str a te d th e d istin g u ish ed a d v a n ta g e s o f th e n e w
p rop osals.
3 E x p a n d in g and in crea sin g p o ssib ility o f th e a p p lica tio n o f IP so u n d in g m e th o d ,
n o t o n ly for n ew m ea su rem en t p ro ject, b u t also for e x p lo itin g an d a d d in g oth er u sefu l
in form ation to su p p o r t th e p ro c essin g an d a n a ly zin g o ld o b ta in ed p r e v io u s IP d a ta T h is
is q u ite a new p rob lem a n d v ery n ecessa ry for th e IP so u n d in g m e th o d
W e co n tin u e t o d ev elo p a n d c o m p le te th is d ire c tio n o f p ro ce ssin g a n d a n a ly zin g th e
IP so u n d in g d a ta b a sin g o n e x p lo itin g th e a b o v e n ew p ro p o sa ls have m a d e by th e a u th o r,
as w ell a s co n tin u e to d ev elo p th is n ew d ire ctio n for 2 D - 3 D a lg o r ith m s.
R e fe re n c e s
1 L ê V iếl D ư K hương, V ũ Đ ức M in h , C ác phương pháp m ới ư o n g đ o sâu điỏn ư ở dùng
tổ hợp hê cực đo hợp lý , T ạ p c h í C á c Khoa h ọ c v ề Trái đ ấ t, 23 3 (2 0 0 1 ), tr 2 1 7 -2 2 4
2 Vu D uc M inh, Le V ie t D u K h u o n g , Som e Induced-P olarization so u n d in g m eth o d s and
th eừ ab ility in in v estig a tin g g e o lo g ic a l m edium , VNU Journal o f Science, N atural
S c ie n c e s , t X V II 4 ( 2 0 0 1 ) , pp 2 8 -3 4
3 Vu D uc M inh , Induced-P olarization Sounding m ethods in a n ew m anner, Jo urnal o f
G eology, S eri B, N o 17, 18(2 0 0 1 ), pp 94-101