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Thermoluminescence investigations of natural calcite crystals of differing genesis
THERMOLUMINt5SCEKCE lNVESTIGAT1ONS CRWJ-ALS OF iXFFER1NG GYMESIS
OF
NATCERAL
CALCITE
Natunl cz~lcitr crystz~ls containing Mn’ +, wxe c~lkctcd from three diflirrcnt - hydrothcrnul, scdimcntary and metamorphic-and cxamincd pvctic aswmblap for their thcrmolumincsccncc characteristics and possible correlation with gcolo_rical
cn+onmcnts of farmarion, FcztturcsapFcJring in their 1k7tu1-Awd xtificially induced TL glow curves stem to indiatc roughly t hc reMi\-c tcmpcnturcs of fornwtions. The TL ycnsitivity of the sample of hydrothermal &sin is the highest amens the three s3mplcs studied, although it h3s the lowzst conccntr;rtion of the TL emittins ccntrcs, viz the snangantsc impurity.
Of all thr: rock fkmin,e mincnls cshibitin : good thcrmoiumincsccncc (TL) scnsitixity~ cafcitc has been studied in detail by carlicr workers to dctcrminc the basic TL mech;lnisms TnWwd ‘(*)_ The buiid-up of TL due to n~tunl unnium and thorium alpha xtivity hi z&o been studied in great dctaif, \i-ith a view to using it as the basis for a method of age determination ‘(“I_ This paper dcscribazs the r#ults obtained in an attempt to corrclatc thcTLchanctcristics with the known gcncsis of natural calcite CryStak
Details of the three sampI_ studied we given in Table I_ The sample wre suriace-cIu~,, pow-d& and the frxtions colkcfcd bctwcn So and 130 muh siw sicvcs were used for the TL measurements- The instruments used to record the TL @low eurwx and the TL cmi&on spectra are the some as described by Nztmbi ct al_= TL glow cun~s were recorded above room tlrmpcrature at about 550 ‘C and at a linear heating nte to about 70 “C and the Iight inknsicies were measured with an EM1 9514s photomultiplicr, l.kual!y 5 mg of the irradiated sJmpkr XIS spread uni-
TABLE
II
The TL emission spectra wnz rccordcd using a 0.15 m Jaw4 Ash Grating Monociwomator and an EM1 9355 QS photomultiplierTO record the TL emission sprum at a particular tcmpcrature about IS mg of the irradiated powder WGIS spread uniformiy over the heater and F&Cssmpk was maintained isothcrmallp at that tcmpcraturc while the monochramacar
was scanned rcpeatcdty bcwccn
200 and 800 nm
a motor drive at a rate of 108 am min’ :_ Gamma irmdiacion ui5s usually carried out inside “Co mmma cells where the dose rate at the sample was 5620 R min- *_ Atpha irradiations wxccarricd OUIusing a 300 ci pklted rrfAm source on 5 mg of finely powdered umpk evenly spread over a circular area of I cm diameterThe sampks, after artificial irradiation, wxc stored in a nrfriscrator until their ‘- TL WEJF read out to minim& the &cay of the earlier part of the TL glow CINYC~ Also. irradhncd sampks wzrc handled in light-tight con8aincrs and under law amgiint ibminatisn in the hbratory KOauoid any unwmrcd r;rposurc to WV rays. TL runs wzrc made in tu;o steps: first, the TL was recorded upto 250 “CT the sampk uzs c&cd to worn temperature. then rchcatcd upta about XXI “C and the TL recorded- While uirgin samples gave TL peaks only at temperatures abwc 250 “C (i-c omiy during the second run yielding b7C the natural thcrmolumi neslmclc) the sampks after arMicial irradiation in the labontar): gave ATL peaks at temperatures below 250 “C also- The calibraIion st NTL sutpufs in terms of equiWent arWicia1 gamma doses was carried out by comparison of outputs obtained in the second runs akr autificiai gamma irradiition to vxiws doses_ using
63
The TL glow peak temperatures obtained in the present srudy have been cornpared with the already published figures in the lircralurc and are @-en in Table 2, The NTL and ATL glow curves for the three samples arc prcsenrcd in Fie_ I and 2, Thcrc is, in ,gxwral, agreement in the puk temperatures_ but an cxtn peak at ldl5 ‘C is xcn only in the cast of szmplc I which is of hydrorhcrmal origin, All three samples exhibit the ~me TL cm’ksion spccfra, peaking broadly at 600 nm, as show-n in Fig_ 3_ The TL age index, (NTL in cquiWcnr gamma dosc)jgross alpha acGvit)s, is c\ssluatcd as discussed by Iambi and Miwa”, and is given in Table 3-
\ i i ii i i
I i i KP
65
(ij Of the three samples riudied for their natural TL. sjmplc kf exhibited a rcla~kcly more promincnl oulpul at kmpcra[ur= below 250 ‘C in addition to the usual NTL peak around 3X0 ‘C_ In Irrms of lhermal decay- this may bc indicake of a gcolhcrmal history of a Iowr avcragc tcmg)erJturecompared to other s;rmplcs_On rhc umc bark smplc I can bc said [CBhave a _~~hcrmal history with the hi$% avcragc rcmpcrarurc. (ii) The ATL @or\- cun-w (Fig_ _ 9 point out that the nrio of 330A’lIO -C peaks ir the highest for UrnpIe bl and iow~t for sample S_ Thermal sensitkricn dudics on CaCO, in this I&ewatery3 haw indieatcd that high kmpenture pc&s appear more pronounced in mmples annuled at hish tcmperaturcs prior to exposure IL may then bc said that perhaps sjmplc M bclonp IO the highcsr.tcmpcrarure of formakw rmang the three mrnpla and ample 5 IO the IOU-H_ Such a concltian dands vindicated from the ,rrrcrlo$caldcwriplians &cn in Table I_ (iii)It is well known that in the TL ofCaC4& u-here mangancsc content is high.
~hc 1ow tcmpcraturc peak is inlcnsc rcfaCvc lo [hc other peaks prcscnl’_ Perhaps lhis is why sample S, u-ilh the high-t Mn conwnt among the three samplesI has yielded the l~wcst \-jluc for the ratio of33Ojl IO ‘C peaks with thosealready (iv) The TL emission 5pcara prcscnfcd in fir- 3 match ~~-cll
available in Iitcraturu:and na doubt rcfcr IQMn” * charactcrislic cmision in ahe C&B3 lattice. While sample I has the [cast hln content among the three sampI= sfudicd, it is infcnrling COnote from fig
Z that sampk I cxhibhs rhc maximum TL sensitivity_ Mn
concentrations in the range of IOOO-3000p-p-m_ as found in the other samples, 151 and S, arc not cxpccfcd to introduce qucnchin,b factors of an order of magyitudc large enough to explain the reduced TL scnsi(iuilicrsof these as compared with sample 1, Perhaps the type of grncsis (hydrothermal in the case of sample 11 has a prominent role in the resulting incrcascd TL sensitkity. most probably by \xa,v of inlroducing suitable lattice defects or to a lcsscr extent, by a sclcctivc inclusion of yet another TL Jcnsiliw impurity
lik
MS
Mg in the carbonate lattice brinp about also a shift in lhe peak position. Mg
in Ca-sires strcn~thcns the crystal field and thus dwrcascs the energy of the &G(;r,,) Raw of Mn”’
which is the emitting ccn:rc ‘C)-
Cw)The limitalions of any TL as estimate on gzologicaielly very old samples hawz been fully discussd with regard COdofomitic limestones in ikmbi and tWitnb, The same corsidcralions hawz been found to bc applicable lo lthcsc cakitcs too and henn: (ML in equivakn% gamma dosc~~~ross alpha activity, is only the 3-L age indCx, =----= $w?n in Tabk 3. whichcould be usedta cakufats the rrlariw ages of rhea samples As in tlhe BolomiGc limestones here also there swns to be a progrcsiw incrc3se in Ihe cxlent of filling up of 3% traps conskituting NTt (in terms of fraclion of possibfie saturation TL kvel in each sampkl with age the sample (Fig. 4). when not
car-of
fully reconstiruRd by metamorphism-
of
Thanks arcduc 10 Dr- A_ K-Can&t, Director, ChemicalGroup. and Shri S_ D_ Scunanr, Head. Health Physics Division, B_A_R_C_, Bombay, for the kind encouragement aalc# offer of laboratory faciiitks in thii inter-institutionalcolhboratiw study, For ftilit’ks for 64d colkction of sampler and other laboratory inucs@atians one of the au@hows(S-M.) acknowfedgcs with fhanks the Head of the Dep~rtroent of Cc&gkal Scknrrs, Jadavpur Uniiuevoity-
67 RI~FERE.~CI~ II[',,]b %V. L_ Prc5~ I ( b ) 'iV. I,_ Pro55.
2 J 4 } 6 7
~,ledlin. i n D . J . ~ l c D o u ~ l l (F~l_).Tisrrmaluminrsrr~rr n/Grolo~.icul .llulrriulfo Acadc=n~ L o n d o n . I ' ~ . pp- 193~-~-~4M c d l i n . i n D - J . M c l ~ u ~ a l l (F~I.). Tl~,,~olumir,r~rrm~" o/Grolo~icul .tlurrriuls, A c a d e m i c l o n d o n . 196S. pp. 91~10~_-
K . S . V . Nambi. V . ~ . i ~ i x a l ~ n d A . K.G~n~u~'.J. Phrs. C. TllgT41440~441~~,L ~ . B,apat a n d K- S. V. ~ a m b i . T h c r m o l u m i n c s c c n c c o f C::,COj: D y a n d C a C O j - Proc..~'utl. ~rmp. T h r ~ l u m i m ' s r r w r r aml itx Apgtirutioos. R A R C . 19T~. pp. 6,19--663. J.F._Vaz:=ndE_T.Z~llcr._4m_Aliml_51.ll~)li54~-116£~J. ~ Yaz., P- J. Kcmmc~" a n d P. W- Lc~'y, in I). J. M c l ) o u ~ a l l led-), T k : , , w l u m i n r s c c n ~ o f G r ~ i ~ l . t ! u f r r i ~ l ~ . Ac:;a~-'mi~: Prc:s~ L o n d o n . 196.~ pp. I I I-1~-_3. K- S- ~.~ .~'~lmbi a n d S. N l i t ~ l . . X ' r ~ r s J u l n ~ . . t l i ~ u l . . i n F . R . Sic~l..Jr. ~ d / n w u l P,rtr, x/_ 3.~. 119631 6~-T~_-
OF
NATCERAL
CALCITE
Natunl cz~lcitr crystz~ls containing Mn’ +, wxe c~lkctcd from three diflirrcnt - hydrothcrnul, scdimcntary and metamorphic-and cxamincd pvctic aswmblap for their thcrmolumincsccncc characteristics and possible correlation with gcolo_rical
cn+onmcnts of farmarion, FcztturcsapFcJring in their 1k7tu1-Awd xtificially induced TL glow curves stem to indiatc roughly t hc reMi\-c tcmpcnturcs of fornwtions. The TL ycnsitivity of the sample of hydrothermal &sin is the highest amens the three s3mplcs studied, although it h3s the lowzst conccntr;rtion of the TL emittins ccntrcs, viz the snangantsc impurity.
Of all thr: rock fkmin,e mincnls cshibitin : good thcrmoiumincsccncc (TL) scnsitixity~ cafcitc has been studied in detail by carlicr workers to dctcrminc the basic TL mech;lnisms TnWwd ‘(*)_ The buiid-up of TL due to n~tunl unnium and thorium alpha xtivity hi z&o been studied in great dctaif, \i-ith a view to using it as the basis for a method of age determination ‘(“I_ This paper dcscribazs the r#ults obtained in an attempt to corrclatc thcTLchanctcristics with the known gcncsis of natural calcite CryStak
Details of the three sampI_ studied we given in Table I_ The sample wre suriace-cIu~,, pow-d& and the frxtions colkcfcd bctwcn So and 130 muh siw sicvcs were used for the TL measurements- The instruments used to record the TL @low eurwx and the TL cmi&on spectra are the some as described by Nztmbi ct al_= TL glow cun~s were recorded above room tlrmpcrature at about 550 ‘C and at a linear heating nte to about 70 “C and the Iight inknsicies were measured with an EM1 9514s photomultiplicr, l.kual!y 5 mg of the irradiated sJmpkr XIS spread uni-
TABLE
II
The TL emission spectra wnz rccordcd using a 0.15 m Jaw4 Ash Grating Monociwomator and an EM1 9355 QS photomultiplierTO record the TL emission sprum at a particular tcmpcrature about IS mg of the irradiated powder WGIS spread uniformiy over the heater and F&Cssmpk was maintained isothcrmallp at that tcmpcraturc while the monochramacar
was scanned rcpeatcdty bcwccn
200 and 800 nm
a motor drive at a rate of 108 am min’ :_ Gamma irmdiacion ui5s usually carried out inside “Co mmma cells where the dose rate at the sample was 5620 R min- *_ Atpha irradiations wxccarricd OUIusing a 300 ci pklted rrfAm source on 5 mg of finely powdered umpk evenly spread over a circular area of I cm diameterThe sampks, after artificial irradiation, wxc stored in a nrfriscrator until their ‘- TL WEJF read out to minim& the &cay of the earlier part of the TL glow CINYC~ Also. irradhncd sampks wzrc handled in light-tight con8aincrs and under law amgiint ibminatisn in the hbratory KOauoid any unwmrcd r;rposurc to WV rays. TL runs wzrc made in tu;o steps: first, the TL was recorded upto 250 “CT the sampk uzs c&cd to worn temperature. then rchcatcd upta about XXI “C and the TL recorded- While uirgin samples gave TL peaks only at temperatures abwc 250 “C (i-c omiy during the second run yielding b7C the natural thcrmolumi neslmclc) the sampks after arMicial irradiation in the labontar): gave ATL peaks at temperatures below 250 “C also- The calibraIion st NTL sutpufs in terms of equiWent arWicia1 gamma doses was carried out by comparison of outputs obtained in the second runs akr autificiai gamma irradiition to vxiws doses_ using
63
The TL glow peak temperatures obtained in the present srudy have been cornpared with the already published figures in the lircralurc and are @-en in Table 2, The NTL and ATL glow curves for the three samples arc prcsenrcd in Fie_ I and 2, Thcrc is, in ,gxwral, agreement in the puk temperatures_ but an cxtn peak at ldl5 ‘C is xcn only in the cast of szmplc I which is of hydrorhcrmal origin, All three samples exhibit the ~me TL cm’ksion spccfra, peaking broadly at 600 nm, as show-n in Fig_ 3_ The TL age index, (NTL in cquiWcnr gamma dosc)jgross alpha acGvit)s, is c\ssluatcd as discussed by Iambi and Miwa”, and is given in Table 3-
\ i i ii i i
I i i KP
65
(ij Of the three samples riudied for their natural TL. sjmplc kf exhibited a rcla~kcly more promincnl oulpul at kmpcra[ur= below 250 ‘C in addition to the usual NTL peak around 3X0 ‘C_ In Irrms of lhermal decay- this may bc indicake of a gcolhcrmal history of a Iowr avcragc tcmg)erJturecompared to other s;rmplcs_On rhc umc bark smplc I can bc said [CBhave a _~~hcrmal history with the hi$% avcragc rcmpcrarurc. (ii) The ATL @or\- cun-w (Fig_ _ 9 point out that the nrio of 330A’lIO -C peaks ir the highest for UrnpIe bl and iow~t for sample S_ Thermal sensitkricn dudics on CaCO, in this I&ewatery3 haw indieatcd that high kmpenture pc&s appear more pronounced in mmples annuled at hish tcmperaturcs prior to exposure IL may then bc said that perhaps sjmplc M bclonp IO the highcsr.tcmpcrarure of formakw rmang the three mrnpla and ample 5 IO the IOU-H_ Such a concltian dands vindicated from the ,rrrcrlo$caldcwriplians &cn in Table I_ (iii)It is well known that in the TL ofCaC4& u-here mangancsc content is high.
~hc 1ow tcmpcraturc peak is inlcnsc rcfaCvc lo [hc other peaks prcscnl’_ Perhaps lhis is why sample S, u-ilh the high-t Mn conwnt among the three samplesI has yielded the l~wcst \-jluc for the ratio of33Ojl IO ‘C peaks with thosealready (iv) The TL emission 5pcara prcscnfcd in fir- 3 match ~~-cll
available in Iitcraturu:and na doubt rcfcr IQMn” * charactcrislic cmision in ahe C&B3 lattice. While sample I has the [cast hln content among the three sampI= sfudicd, it is infcnrling COnote from fig
Z that sampk I cxhibhs rhc maximum TL sensitivity_ Mn
concentrations in the range of IOOO-3000p-p-m_ as found in the other samples, 151 and S, arc not cxpccfcd to introduce qucnchin,b factors of an order of magyitudc large enough to explain the reduced TL scnsi(iuilicrsof these as compared with sample 1, Perhaps the type of grncsis (hydrothermal in the case of sample 11 has a prominent role in the resulting incrcascd TL sensitkity. most probably by \xa,v of inlroducing suitable lattice defects or to a lcsscr extent, by a sclcctivc inclusion of yet another TL Jcnsiliw impurity
lik
MS
Mg in the carbonate lattice brinp about also a shift in lhe peak position. Mg
in Ca-sires strcn~thcns the crystal field and thus dwrcascs the energy of the &G(;r,,) Raw of Mn”’
which is the emitting ccn:rc ‘C)-
Cw)The limitalions of any TL as estimate on gzologicaielly very old samples hawz been fully discussd with regard COdofomitic limestones in ikmbi and tWitnb, The same corsidcralions hawz been found to bc applicable lo lthcsc cakitcs too and henn: (ML in equivakn% gamma dosc~~~ross alpha activity, is only the 3-L age indCx, =----= $w?n in Tabk 3. whichcould be usedta cakufats the rrlariw ages of rhea samples As in tlhe BolomiGc limestones here also there swns to be a progrcsiw incrc3se in Ihe cxlent of filling up of 3% traps conskituting NTt (in terms of fraclion of possibfie saturation TL kvel in each sampkl with age the sample (Fig. 4). when not
car-of
fully reconstiruRd by metamorphism-
of
Thanks arcduc 10 Dr- A_ K-Can&t, Director, ChemicalGroup. and Shri S_ D_ Scunanr, Head. Health Physics Division, B_A_R_C_, Bombay, for the kind encouragement aalc# offer of laboratory faciiitks in thii inter-institutionalcolhboratiw study, For ftilit’ks for 64d colkction of sampler and other laboratory inucs@atians one of the au@hows(S-M.) acknowfedgcs with fhanks the Head of the Dep~rtroent of Cc&gkal Scknrrs, Jadavpur Uniiuevoity-
67 RI~FERE.~CI~ II[',,]b %V. L_ Prc5~ I ( b ) 'iV. I,_ Pro55.
2 J 4 } 6 7
~,ledlin. i n D . J . ~ l c D o u ~ l l (F~l_).Tisrrmaluminrsrr~rr n/Grolo~.icul .llulrriulfo Acadc=n~ L o n d o n . I ' ~ . pp- 193~-~-~4M c d l i n . i n D - J . M c l ~ u ~ a l l (F~I.). Tl~,,~olumir,r~rrm~" o/Grolo~icul .tlurrriuls, A c a d e m i c l o n d o n . 196S. pp. 91~10~_-
K . S . V . Nambi. V . ~ . i ~ i x a l ~ n d A . K.G~n~u~'.J. Phrs. C. TllgT41440~441~~,L ~ . B,apat a n d K- S. V. ~ a m b i . T h c r m o l u m i n c s c c n c c o f C::,COj: D y a n d C a C O j - Proc..~'utl. ~rmp. T h r ~ l u m i m ' s r r w r r aml itx Apgtirutioos. R A R C . 19T~. pp. 6,19--663. J.F._Vaz:=ndE_T.Z~llcr._4m_Aliml_51.ll~)li54~-116£~J. ~ Yaz., P- J. Kcmmc~" a n d P. W- Lc~'y, in I). J. M c l ) o u ~ a l l led-), T k : , , w l u m i n r s c c n ~ o f G r ~ i ~ l . t ! u f r r i ~ l ~ . Ac:;a~-'mi~: Prc:s~ L o n d o n . 196.~ pp. I I I-1~-_3. K- S- ~.~ .~'~lmbi a n d S. N l i t ~ l . . X ' r ~ r s J u l n ~ . . t l i ~ u l . . i n F . R . Sic~l..Jr. ~ d / n w u l P,rtr, x/_ 3.~. 119631 6~-T~_-