VNU JOURNAL OF SCIENCE, Mathematics - Physics T XVIII, Nq - 2002 TH E ADVANTAGES OF TH E N EW IN T H E IM P R O V E D P O L A R IZ A T IO N PRO PO SA LS S Y M M E T R IC S O U N D IN G IN D U C E D M ETHOD Vu D u e M in h C o lleg e o f S c ie n c e , V N U A b s tr a c t T h e higher resolution, greater investigating depth, increasing reliability of ge ology forecasting results and possibility of expanding the application of the improved symmetric induced polarization sounding method have been illustrated by theoretical and field medium are th e advantages of the new proposals presented in this article I I n tr o d u c tio n III th e article [2], th e our n ew p rop osals, e sp ecia lly th e P etro v sk i in d u ced p o la r iz a tio n (IP ) p aram eter r/p, h a v e b een in tro d u ced for d a ta p ro cessin g in th e in d u ced p o larization so u n d in g m eth od ; a s a resu lt, th eir a d v a n ta g es in co m p a riso n to th e p reviou s ven tion al p a m eters have b een illu stra ted by ca lc u la tin g for th e th eo retica l m ed iu m H ow ever, th e P etrovsk i tra n sfo rm in g form ula co n ta in s d eriv a tio n w h ich is n ot sta b le, so d esired resu lts are not alw ays o b ta in ed W ith p u rp o se to o v erco m e th e se d isa d v a n ta g es, w e have p rop osed th e im proved sy m m etric electro d e array and th e co rresp o n d in g m easu re m ent procedure, th e sim p le a lgeb raic tra n sfo rm a tio n s (w ith o u t th e d eriv a tio n ) to ap p ly to th e resistiv ely sou n d in g m e th o d [ l] T h o se im p roved s y m m e tr ic e le c tr o d e array and tran sform atio n s are o f scien tific arid p ctica l sign ifican ce B a sin g o n th o se research es, w e a lso have p rop o sed th e im p roved sy m m etric IP so u n d in g m e th o d (IS IP S ) a n d it h a s b een te ste d effectiv ely as th e article [3] In th is a rticle, w e w ill illu str a te th e correctn ess a n d a d v a n ta g es o f th e new p rop osals in the IS IP S by th eo retica l an d p ctica l m edium ; p r o p o sin g p o s sib ility o f ex p a n d in g and achieve b e tte r geological effectiv e o f th e n ew p rop osals to 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 co n v en tio n a l IP so u n d in g m eth o d I I B a sics o f t h e new p ro p o s a ls in t h e im p ro v e d s y m m e tr ic in d u c e d p o la riz a tio n s o u n d in g m e th o d I I 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 he apparent p o la riza tio n is c a lc u la te d by th e fo llo w in g form ula: Vk = p*k- Pk/Pkt (!) w here pị a n d pk are the ap p aren t re sistiv itie s o f th e p o la rized an d n o n - p o la rized m ed iu m , resp ectively, corresp on d in g to th e r e sistiv ity p a m eters p i a n d Pi w h ich are rela ted by: p* = P i / ( I — r/i) w here i is th e m ed iu m m o d el in d ex T y p e s e t by 13 14 V u D u c IM in h B a sin g on th e a b o v e d efin itio n s, w e h ave also d efin ite th e n ew I P p a m eters [2] sim ilarly: - T h e p o la riza tio n o f th e sy m m etric In d u ced P o la riza tio n so u n d in g m ethod: rj9 - T h e p o la riza tio n o f th e (lip o le-a x is In d u ced P o la riza tio n so u n d in g m ethod: r)r - T h e P etr o v sk i p o la riza tio n : Tjp II T h e n e w t r a n s fo r m a tio n s A ccord in g to [3], th e im p ro v ed sy m m etric In d u ced P ola riza tio n so u n d in g ele c tr o d e array is a llo c a te d a s th e follow ing: m m , a b n , n, — • - • ♦ -♦ - • • -w here, w ith o n e cu rre n t-electro d e sep a tio n A B , from th e m ea su rem en t w e m ay o b ta in Psi(r i)> Vsi(r \) a n d Ps (r 2)>Vs2 (r ), co rresp o n d in g to rj and r In such a way curve Pi \ , Pi2 a n d TỊS\ , ri„ a re o b ta in e d T h en : ^ LS ( a M S -frJ' / 0\ (2) where psr - the dipole-axis resistively sounding curve obtained by transform ing from th(! s y m m e tric re sistiv e ly so u n d in g c u rv e p a T h e v a lu es o f P etro v sk i r e sistiv e ly so u n d in g cu rve ppar are ca lcu la ted by the follow ing form ula: Ppsr = p j ( p sr/ p a - 1) (3) T h e n a ll th e n ecessa ry in fo rm a tio n w ill b e ca lcu la ted accordin g to th e sc h e m a show n o n figure Figure S ch em a ca lcu la tin g p a m eters by u sin g IS IP S array The a d v a n ta g e s o f th e n e w p r o p o s a ls i n th e i m p r o v e d s y m m e t r i c 15 I I I C h e c k in g t h e m u tu a l p rin c ip le W e have m easu red an d c a lcu la ted ex p erim en ta lly th e m u tu a l p rin cip le on th e field m ed iïiu n Below w e present o n ly th e ex a m p le resu lt in T an D an - H o a n h B o - Q u an g N in h F igure sh o w s the ap p aren t resistiv ely cu rves prstr (rorstr) p r a ctic a lly m easu red by t h e im p ro v ed sy m m etric so u n d in g array M A B N , Prsng (rorsn g) p r a c tic a lly m ea su red by th e im p r o v e d sy m m etric sou n d in g array A M N B and th e co rresp o n d in g P etro v sk i resistiv e ly s o u n d in g curves F igu re sh o w s the P etrovsk i resistiv ely cu rves ỌyrstT (rop rstr) for array MA B N and Pprsng (roprsng) for array A M N B ; th e P etrovsk i resistiv ely cu rv es Pprsxd (rop rsxd ) derived fro m th e tran sform ation o f th e v a lu es Pr p ctica lly m ea su red by th e ID A IP S array and n e v a lu e Prjxd(r max) m easured by th e eq u atorial d ip o le array a t fin al siz e p max o f the I D A I P S array ị ; : ; ; ; i Ỵ i -i- i — ro rs* ro rsrỗ j ro p rs tr f c p re n g 10*1 - — * — - *• — -— - ~.-iU 10° to’ 1Ơ* Figure C urves p rstr (rorstr), p rsng (rorsng) an d corresponding Petrovski curves W e realize th a t curves are fitted T h is proves th a t th e m u tu a l p rin cip le is right for a ll th e arrays, th e electro d e sp acin g, th e m ea su rem en ts as w ell a s th e tra n sfo rm a tio n s th a t h ave b e e n u sed to confirm th e m eth o d IV C o n firm in g t h e c o rre 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 ro p o s a ls I V Calculating values o f the polarization sound ing curves ★ The threc-laycred g CO-electrical model B y sim u la tio n m eth o d in P C , w e have b u ilt th e p ro g m s o f calfculating th e p o la r iza tio n so u n d in g cu rves on layered g e o e le c tr ic a l m o d e ls for d ifferen t ele c tr o d e array by M atlab lan gu age W o on ly give a sp ecific ex a m p le o f th e th ree-la y ered g eo -electrica l m o d el as follow in g: pi = [14.51]; TỊi = [241); h x = [15]; w ith i = , , F ig u r e sh ow s th e th eo retica l ID A IP S curve Tịr (eta r) a n d th e cu rv e corresp on d in g to the ID A I P S cu rves 7]sr (eta sr) o b ta in e d by tra n sfo rm a tio n 16 V u DĩẦc M i r t h F igu re sh ow s th e th eo retica l P etrovsk i curve T)p (eta p ) an d th e Petrovski cu rv e vpsr (etap sr) o b ta in ed by tran sform ation F igure T h e th e o r e tic a l cu r v e rjr (etar) a n d cu r v e ĨỊsr (e ta sr ) o b ta in e d by tr a n s fo r m a tio n Figure T he theoretical curve 7]p (etap) and (etapsr) obtained by transformation ★ The field m edium T h e te stin g ca lcu la tio n s h ave b een p erform ed in Tan D an - H oan h B o - Q uang N in h and D akson g - G ia Lai B elow w e o n ly p resen t th e ex a m p le curves m ea su red at point 22 o f th e profile S l l in D aksong - G ia Lai F ig u re shows cu rv e 7]r (e ta r) p c tic a lly m easu red by th e ID A IP S array; th e ID A IP S curves 7]sr (etasr) and r]p3r (eta p sr) o b ta in ed by tran sform ation o f carves p8) TỊa p ractically m easu red by th e IS IP S array an d par F igure T h e p ctic a l cu rv e 7]r (eta r) a n d c u r v e 7/irx(e ta sr ), 7J (eta p sr) o b ta in e d by tr a n s fo r m a tio n In com p arin g, p ctica l m easu red cu rves and corresponding cu rves ob tain ed by tran sform ation are nearly fitted , o n ly th e v a lu es at som e final sizes is n o t th e sam e T h is proves th e correctn ess o f th e algebraic tran sform ation s m en tio n ed a b o v e B esid es, Petrovski curve also h as reflected clearly resolu tion a b ility - th a t is it s a d van tages I V P ro c e ssin g d a ta o n th e p ro file T h e new p rop osals h ave b e e n ap p lied in tw o directions: P ro cessin g and a n a ly zin g d a ta o b ta in ed p reviously b y th e n orm al IP sounding 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 17 m eth o d in order t o ex p lo it and add oth er u sefu l in form ation in tw o ways: 4- In terp o la tin g values o f curves TỊk and pk o b ta in ed p reviou sly by the norm al IP sou n d in g m eth o d to valu es o f th e im p roved IP curves w ith th e correspon d in g sizes o f electrod e sp acin g an d coefficients -f Prom th e sizes o f n orm al electro d e array, ca lcu la tin g corresp on d in g coefficients o f th e im proved electro d e array P ro cessin g a n d a n a ly zin g d a ta o b ta in ed by th e IS IP S m eth o d B elow w e p resen 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 tain ed p reviously b y the n orm al S IP S m eth o d on profile 20 in S o n g G iang - Q u an g N am , w hich were m easu red by U n io n o f P h y sic-G eo lo g y in 1999 ★ The results o f processing and analyzing data obtained previously by the normal SIP S method on profile 20 (see figures 7, ) • Line 20 w a s form ed in th e N o rth ea st - S o u th w est d irectio n p erp en d icu larly to the folding stru ctu re w ith N o rth w est - S o u th ea st d irection in th e S o u th e a st o f G iang R iver Figure C ontour section Tị on th e profile 20 (%) (S o u rc e : U n io n o f P h y sic -G e o lo g y ) • A lon g th e profile, th e fo llow in g m a in geological form ation s are identified: -f B en g ia n g - Q u e son m a g m a com p lex: GE OL OGI C A L SECTION IN GIANG RIVEK 200 400 600 QUANG NAM 800 1000 Figure : Geological section of th e profile 20 (S o u rc e : U n io n o f P h y sic -G e o lo g y ) 1200 18 V u D uc M in h M ain com p on en ts: blende gran od iorite, b io tite hornblende, an d to r a n ite b iot.te h o r n Specific p h ysical fea tu res are resistiv ity w ith p = 2, 000 — ,0 0 ohm s.m po larization 7/fc = — 5% D irections: G ranod iorite o f B en G ian g - Q u e son com p lex, p h a se 2; S ch ist o f K ham d u e form ation , layer 3; S ch ist o f K h a m D u e form ation, layer 2; 4- A ltered zones; Faults; V ents o f gold-sulfuric quartz + T h e m etarnorphic sed im en tary rocks o f K ham D u e fo rm a tio n sist of: - U p p er layer: b io tite - gran ite quartz shale, m ica quartz, an d p lagioelase - bi- otite quartz Specific physical features are resistivity w ith p = 1,000 — 2,000 ohm s.m , p olarization w ith T]k = — 4% - Lower layer: B im ica gn eis, b im ica quartz, b io tite g n eis, sch ist, a n d b iotite qu artz Specific p h ysical featu res are resistiv ity w ith p = 500 - ,0 0 o h m s.m , stim u la ted p o la r ization w ith 7]k = — 4% M etam orp h ic sed im en ta ry form ation s w ere stro n g ly fold ed an d divided by deep fau lts p erp en d icu larly w ith th e surveyed profile A lo n g th e fa u lts, rocks are stro n g ly d estro y ed a n d in filtra te d by sulfu ric ores D estroyed zone h a s sm all re s istiv ity p = 0 —500 o h m s.m and high p o la riza tio n T]k = — 5% G old b ea rin g p o ly m eta l surphide - quartz zo n es h ave th e r e sistiv ity relevan t to altered zon es and high p o la riza tio n rjk = — 10% • T h e aim o f the IP so m id in g m eth o d is to solve th e fo llow in g tasks: + T o stu d y folded stru ctu res along th e surveyed profile; 4- To define gold b ea rin g su rp hide - quartz zones ★ The results o f applying the new proposals to exploit data W ith a p p ly in g th e n ew p rop osals to ex p lo it d a ta o b ta in ed p rev io u sly by th e norm al S IP S m eth o d on profile 20 in S on g G ian g - Q u a n g N a m th en tou r sectio n s o f p olar ization have b een ca lcu la ted and reported B elow w e o n ly present, th e ex a m p le co n to iư sectio n s T)sr and Tjpsr o n figures 9, 10 F igure C on tou r se c tio n 7]sr (%) T h e a d v a n ta g e s o f th e n e w p r o p o s a ls i n th e i m p r o v e d s y m m e t r i c 19 Figure 10 Contour section 77pnxd (%) The results of applying the new proposals in the ISIPS to exploit d a ta obtained on profile 20 in S on g G ian g - Q u a n g N a m can b e seen th at: -f Detail division of geological components in the section; - M agm a tic gra n o d io rite form ation is ch aracterized by r e sistiv ity 2,000 - 3,000 oh m s.m , p o la riza tio n - 5%; - M etam o rp h ic sed im en ta ry rocks o f K h am D u e form ation s are characterized by resistiv ity 1,000 - '2,000 o h m s.m , p o la riza tio n - 5% + T h e b roken zone, d e s tn ic te d alo n g th e fa u lts is d e a r ly d efined T h is zon e is ch aracterized by low resistiv ity ‘200 - 800 o h m s.m , p o la riza tio n - 8%; defining in m ore d eta il th e gold b ea rin g sur phi d e - quartz zon es w ith th e p o la riza tio n from to 10% T h e contour se c tio n TỊpsr, severally, d efined clearly and in d eta il th e v en t b o d ies w ith the polarization from to 10% We see clearly that 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 more clearly V C o n c l u s io n s For th e first tim e, th e P etro v sk i IP p aram eters (esp ecia lly r/p) h ave b een p r o p osed and th eir scien tifica lly th eo retica l b a se b u ilt and a d v a n ta g es th a t th ey ex h ib it higher reso lu tio n a n d g re a te r in v e stig a tin g d e p th th a n th e co n v en tio n al p a m e te rs pki Vk have been confirmed by us 2ã T h e n ew p ro p o sa ls in th e IS IP S h ave h igh scien tific relia n ce, really usefulness, and scientific and practical significance T hey elim inated the fundam ental disadvantage th at the transform ation between 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 formulas to transform curves Creating algorithm s of processing and analyzing the data using the new proposals in the ISIPS basing on selecting reliable information with comprehensiveness T hey also have m ade the geology forecasting results clearer and 20 V u D u c M in h m ore reliable, reflected th e nearly real IP effect o f stu d y o b jects, in crea sed resolu tion o f weak an om alies A ll o f th o se h ave illu stra ted the d istin gu ish ed a d v a n ta g es o f th e n ew proposals E x p a n d in g and in creasin g p o ssib ility o f th e a p p lication o f IP so u n d in g m e th o d , n ot on ly for n ew m easu rem en t p ro ject, b u t also for ex p lo itin g and a d d in g oth er u seful inform ation to su p p o rt th e p ro cessin g and an a ly zin g o ld o b ta in ed p rev io u s IP d ata T h is is q u ite a new problem an d very n ecessary for th e IP so u n d in g m eth o d W e tin u e to d evelop an d co m p lete th is d irectio n o f p ro cessin g an d an a ly zin g th e IP sou n d in g d a ta b asing o n e x p lo itin g th e ab ove new p rop osals have m a d e by th e au th or, as w ell as tin u e to d evelop th is new d irection for 2D - 3D a lg o rith m s R eferen c es L ê V iếl Dư K hương, V ũ Đ ức M inh, C ác phương pháp m ới o n g đo sâu điỏn dùng tổ hợp cực đo hợp lý, T p c h í C c Khoa h ọ c v ề Trái đ ấ t, 23 (2 0 ), tr 217 -2 Vu Duc M inh, Le V iet Du K huong, Som e Induced-Polarization soun d in g m ethods and th eừ ability in in vestigating 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 (2 0 ), pp -3 Vu D uc M inh, Induced-Polarization Sounding m ethods in a n ew manner, Journal o f G eology , Seri B, N o 17, 18(2001), pp 94-101 ... curves Creating algorithm s of processing and analyzing the data using the new proposals in the ISIPS basing on selecting reliable information with comprehensiveness T hey also have m ade the geology... ith the polarization from to 10% We see clearly that applying the new proposals in the ISIPS to calculate the ap parent resistivity and polarization values perm its defining research objects in. .. elim inated the fundam ental disadvantage th at the transform ation between curves through the unstable derivation existed for a long time One of the advantages of our proposal is only using the