E 第 Sci.Rep.KanazawaUniv. , Vol.12 , No.1 , pp.21-66 June1967 Studies on the Dating Methodsfor Quaternary Samples by Natural Alpha-Radioactive Nuc 1i des I. 1ntroduction KazuhisaKOMURA * andMasanobuSAKANOUE Radiochm 伺:icalLaboratory , De ρ ar , 初伽t01 Chemistry Facul か 01Science , KanazawaUniversity (Received.4May1967) CONTENTS 1-1 1ntroduction …・・…H ・ H ・.・H ・ .... ・H ・.・H ・ .... ・H ・H ・ H ・ H ・ ..... ・H ・ ..... ・H ・ ..... ・H ・ ..... ・H ・..,….23 1-2 HistoryoftheExcess230Thand231PaMethodsforPleistocene Dating ・ H ・ H ・-….25 1-3 HistoryoftheDeficient230Thand231PaMethods forPleistoceneDating ・ H ・ H ・ ..25 1 -4 OtherPossibleMethodsforPleistoc 叩 e Dating .・H ・ .... ・H ・ .... ・H ・-… .... ・H ・ ..... ・H ・ ...26 1-5 PurposesofThisWork .・H ・.・H ・ .... ・H ・-… ..... ・H ・ ........ ・H ・ .... ・H ・ ........ ・H ・.・H ・-…27 II. TheoryoftheDeficient230Thand231PaMethodsforPleistoceneDating II-1 General ・ ...... ・H ・.・H ・.・H ・.・H ・ ..... ・H ・ .......... ・H ・ ..... ・H ・ ..... ・H ・ .... ・H ・ .... …...・H ・ .... ・H ・ .27 II-2 SignificanceoftheUranium1sotopicRatio234U /238U・ H ・ H ・ ..... ・H ・ H ・ H ・..…...・H ・ ..28 II-3 RelationBetween230Thand Uranium 1sotopes234Uand238U・ H ・ H ・ H ・ H ・ ..... ・H ・ ..31 II -4 RelationBetween231Paand It sParent235U・ H ・ H ・..…...・H ・ ..... ・H ・ H ・ H ・ ..... ・H ・...…..33 II-5 RelationBetween 231Pa and230Th・ H ・ H ・ ..... ・H ・ ..... ・H ・ ..... ・H ・ H ・ H ・ ..... ・H ・ H ・ H ・'"….'34 II-6 OtherUsefulMethodsforAgeCalculation . ・H ・ ....... ・H ・ H ・ H ・.・H ・ ...... ・H ・.・H ・…-・35 II I. ApparatusesandChemicals 1II-1 Apparatuses... ・ H ・ H ・ H ・ ..... ・H ・ ..... ・H ・ ..... ・H ・…・……H ・ H ・ ..... ・H ・.・H ・.・H ・ ..... ・H ・ ..... ・H ・ .36 1II-2 Chemicals …...・H ・ ..... ・H ・ ..... ・H ・ ..... ・H ・-…...・H ・-…...・H ・ ..... ・H ・ ..... ・H ・ ..... ・H ・ ..... …...・H ・ .37 fV. Samples 1V-1 Purposesof An alysis . ・H ・ H ・ H ・..…...・H ・ .... ・H ・..,・・H ・ H ・..…...・H ・.・H ・.・H ・ ..... ・H ・ .... 37 1V -2 SampleDescriptions …・・…H ・ H ・ ...... ・H ・..…H ・ H ・...…H ・ H ・...0' ........ ・H ・..…...・H ・..…・・…・・37 V. An alyticalProcedures V-1 SampleDecomposition …...・H ・ ..... ・H ・..…...・H ・ ..... ・H ・-……H ・ H ・.・H ・ ..... ・H ・ ..... ・H ・..…・40 V-2 1nitial Co ncentrationofRadioactiveElementswithHydroxidePrecipitate . ・H ・・…・40 V-3 1nitialSeparationofRadium , Thorium , ProtactiniumandUranium by An ion ExchangeMethod ....... ・H ・.・H ・ .......... ・H ・ ......... ・H ・ ............ ・H ・ ...... ・H ・ ........ ・H ・.・H ・ 41 V -4 PurificationandElectrodepositionof Thorium 1sotopes …...・H ・..……H ・ H ・.・H ・..…42 V-5 PurificationandElectrodepositionofProtactinium1sotopes... ・ H ・ ..... ・H ・ ..... ・H ・ .... ….43 V -6 Purificationand El ectrodepositionofUranium1sotopes... ・ H ・ ..... ・H ・ ..... ・H ・-…H ・ H ・-…43 V I. Measurements .... ・ H ・ ..... ・H ・..…...・H ・..…...・H ・..…...・H ・..…・・…...・H ・ ..... ・H ・-… .... ・H ・.・H ・..…・・45 V1 I. Resu 1t s andDiscussion VII-1 UraniumAssay ・ H ・ H ・ ..... ・ * Present address Otozai Laboratory , Department of Chemistry , Facu 1t y of Science , Osaka University. - 21-
46
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E第
Sci. Rep. Kanazawa Univ., Vol. 12, No. 1, pp. 21-66 June 1967
Studies on the Dating Methods for Quaternary Samples
by Natural Alpha-Radioactive Nuc1ides
I. 1ntroduction
Kazuhisa KOMURA * and Masanobu SAKANOUE
Radiochm伺:icalLaboratory, Deρar,初伽t01 Chemistry
Faculか01Science, Kanazawa University
(Received. 4 May 1967)
CONTENTS
1-1 1ntroduction …・・… H ・H ・...・ H ・....・ H ・...・ H ・....・ H ・・・・ H ・H ・H ・.....・ H ・.....・ H ・.....・ H ・.....・ H ・..,….231-2 History of the Excess 230Th and 231Pa Methods for Pleistocene Dating ・H ・H ・-….251-3 History of the Deficient 230Th and 231Pa Methods for Pleistocene Dating ・H ・H ・..251-4 Other Possible Methods for Pleistoc叩 eDating ....・ H ・....・ H ・....・ H ・-…....・ H ・.....・ H ・...261-5 Purposes of This Work ....・ H ・....・ H ・....・ H ・-….....・ H ・........・ H ・....・ H ・........・ H ・....・ H ・-…27
II. Theory of the Deficient 230Th and 231Pa Methods for Pleistocene Dating II-1 General ・......・ H ・...・ H ・....・ H ・...・ H ・.....・ H ・..........・ H ・.....・ H ・.....・ H ・....・ H ・....…...・ H ・....・ H ・.27II-2 Significance of the Uranium 1sotopic Ratio 234U / 238U・H ・H ・.....・ H ・H ・H ・..…...・ H ・..28II-3 Relation Between 230Th and Uranium 1sotopes 234U and 238U・H ・H ・H ・H ・.....・ H ・..31II-4 Relation Between 231Pa and Its Parent 235U・H ・H ・..…...・ H ・.....・ H ・H ・H ・.....・ H ・...…..33II-5 Relation Between 231Pa and 230Th・H ・H ・.....・ H ・.....・ H ・.....・ H ・H ・H ・.....・ H ・H ・H ・'"….'34II-6 Other Useful Methods for Age Calculation ...・ H ・.......・ H ・H ・H ・...・ H ・......・ H ・....・ H ・…-・35
III. Apparatuses and Chemicals 1II-1 Apparatuses...・H ・H ・H ・.....・ H ・.....・ H ・.....・ H ・…・…… H ・H ・.....・ H ・...・ H ・....・ H ・.....・ H ・.....・ H ・.361II-2 Chemicals …...・ H ・.....・ H ・.....・ H ・.....・ H ・-…...・ H ・-…...・ H ・.....・ H ・.....・ H ・.....・ H ・.....…...・ H ・.37
fV. Samples 1V-1 Purposes of Analysis ...・ H ・H ・H ・..…...・ H ・....・ H ・..,・・ H ・H ・..…...・ H ・....・ H ・...・ H ・.....・ H ・....371V -2 Sample Descriptions …・・… H ・H ・......・ H ・..… H ・H ・...… H ・H ・...0'........・ H ・..…...・ H ・..…・・…・・37
V. Analytical Procedures V-1 Sample Decomposition …...・ H ・.....・ H ・..…...・ H ・.....・ H ・-…… H ・H ・...・ H ・.....・ H ・.....・ H ・..…・40V-2 1nitial Concentration of Radioactive Elements with Hydroxide Precipitate ...・H ・・…・40V-3 1nitial Separation of Radium, Thorium, Protactinium and Uranium by Anion
Exchange Method .......・ H ・...・ H ・..........・ H ・.........・ H ・............・ H ・......・ H ・........・ H ・...・ H ・41V -4 Purification and Electrodeposition of Thorium 1sotopes …...・ H ・..…… H ・H ・...・ H ・..…42V-5 Purification and Electrodeposition of Protactinium 1sotopes...・H ・.....・ H ・.....・ H ・....….43V -6 Purification and Electrodeposition of Uranium 1sotopes...・H ・.....・ H ・.....・ H ・-… H ・H ・-…43
VI. Measurements....・H ・.....・ H ・..…...・ H ・..…...・ H ・..…...・ H ・..…・・…...・ H ・.....・ H ・-…....・ H ・...・ H ・..…・・45
V1I. Resu1ts and Discussion VII-1 Uranium Assay ・H ・H ・.....・
* Present address Otozai Laboratory, Department of Chemistry, Facu1ty of Science, Osaka University.
- 21-
22 Kazuhisa KOMURA and Masanobu SAKANOUE
VIII. DiscussIons on the Causes of Error VIII-1 Pipetting Error and th巴 Absolute Activity of 232U …""…..,0・H ・-ローH ・H ・..・..・ o・...…・57VIII-2 Impurities in Tracer Solution ..…・........日……"....・H ・-ー……口一……ー…・…h ・..........58VIII-3 Counting Errors.......園……........,・..,.....,.....,...・回目 …口ー・ …......園園 a・......…・ 8・0"_・H ・H ・.59VIII-4 Contamination.....…・・…ー…・・・……日....・H ・....,......……日…・……日…・…...・・……・………・61
IX. Comparison of the Results with Other Data ・H ・H ・..・・・H ・H ・.......,・H ・e・e・....…...・H ・.......…,,63
the available range of this method back to about 40,000 years, and the gap b色tween
million years determined by mass spεctrometric methods and seγ巴ra1ten thousand
years radiocarbon method still remained to be filled with other useful method
for dating.
Stlf.dies 01'1 the Dating且ifethods 101' (Ju,af,ωnar.v Sa狩ltles 25
[-2 History of the Excess 230Th (Ionium) and 231Pa (Protactinium) 1¥1ethoc1s for
PleistocenεDating
From th告 viewpoint of half-lives, 230Th (75,200 yr) and 231Pa ,480 yr) are
very aUractive for Pleistocenピ ag己 determination. This was pointed out first by
Khlopin (2) for the age determination of seconclary ur旦niumminera1s, but had not
b巴己11re且lizedfo1' a long time because of the difficulty of the di1'ect determination of
230Th or 231Pa. The fact discovered by Joly (1908) that the radillm content in sea
sedimεnt cor巴 ismuch greater than that in terrestrial materials, was reaHirmed by
Piggot ancl Urry (3) in 1942, and this bec呂methe initiation of the excess 230Th
method (th巴 useof 230Th cl己C旦yin samplε) for Pleistocene clating of sea sediments.
This m色thodhad been improvecl greatly by the direct clet巴rmm乱tionof 230Th (4) and
by the aivances of the ap;J品ratus己sfor alpha spectrometric measurement. Though
日.1anyworks have b吉正~n carried out in this direction, the accumulation of the analy-
tical clata showecl th色 possibilityof th色 migrationof 2301、hitself in and out the
sample and the exc巴ss230T11 method was sometimes proved to be erroneous for th巴
dating of the seclim巴ntationrate of thεse且 seclim己nts.
On the other hand, the use of 231p旦 asa too1 for agεcletermination was put
into practice only recent1y by Rosholt (5) in 1961, bec乱us記 ofthe extremely low
concentration of 231Pa in natural samples ancl of its troubl邑 behavioursin chemical
treatment. Recently several investigations as 1:0 the excess 231Pa methocl use
of 231Pa decay in the sample) ¥vere carried out by the sciεntists mainly in U. S. A.
ancl lJSSR. Sarma (6) investigatecl the accumulation rate of the cleep sea sεcliment
by llsing excess 231Pa and 2:>OTh methocls and confirmed thεusefulness of the ratio
231Pa/230Th for clating. Furth匂司 investigationby Sackett et al. (7) showed that the
excεss protactinium method afforcls much mor巴 reliabledata than th巴 εxcess230Th
method, if the clata obtained by thes日 twomethods were compared with radiocarbon
data.
1 -3 History of the Defici巴nt230Th and 231.pa Methods for Pleisto田 neDating
Since Barns et al. (8) hacl shown the possibility of using the degree of the
d邑ficiencyof 230Th with resp巴ctto its parent 234U as an age indicator for coral
cuttings of P品cificatoll, many works have been made. Sackett (9) analyzed many
marine carbonates and obtained the good agreement of thε230Th ages with radiocaト
bOI1 ages. Furthεr studies by Tatsumoto and Golclberg (10) emphasizecl the contriblい
tion of il1itial 230Th ancl proposed the 232Th content as an inclicator for correction.
1n 1955, Cherdyntsev (11) made an import乱ntcliscovery that the activity ratio
of 234Uj238U is not llnity and 234U anomaly occurs rather commonly in natural
condi tions. Th巴 authorpointecl out the need of correction for age calculation by the
230Th growth method. 1n this respect Cherdynts巴v(12) mad巴 anage determin呂tion
of thεfossi1 bon巴scoUectecl frol11 th巴間mainsof anciel1t civilization (Kostenki, 1¥10闘
lodovo, cavεKuclaro, etc.) and obtained very useful r巴su1tsfor archaeological stuclies.
26 Kazuhisa KOMURA and Masanobu SAKANOUE
They had used the simple thorium isotope m巴thodusing the ratio 230Th/234Th
instead of direct det色rminationof 234U activity and the othεrm巴thodusing the ratio
227Thf234Th instead of 231Paf235U. They a1so suggested the possibility of the
dating method using th邑 decayof 234LJ (248,000
Thurber (13) confirmed the exsistence of 234U anoma1y a1so in sea water and
marine carbonates and proposed the 234LJf238LJ dating m巴thod,which may be ap-
p1icable back to about one million years. The ratio 234Uf238U obtained from many sea water samples showed a11 good agreement within the range of statistical error
(r= 1.15土0.02),which may be taken as th色 initial234U f238U ratio in a11 sort of
marin巴 carbonatesamples.
Though Rosholt et aL (14), Sackett and Potratz (15) had suggested the use of
231Pa/235U ratio for cross checking the reliability of 230Th dating method多 the
activity of 231Pa was too small to be measured accurately without developing the
detector with very low background activity and with high counting efficiency. Ac-
cordingly, other criteria had to be sought to confirm the assumption of the closed
system Ior 230Th d呂tingmethod. Broecker (16) and Blanchard (1'7) studied many
corals and molluskan shells collected from various regions in the world. Based on
th告 analyticalresults of U /Ca, Ra/Ca and uraniurn series dis巴quilibrium in the
sample, th色Y 巴mphasizedthat the 226Raf230Th ratio was very useful criterion for
confirmation of the c10sed system. Recεntly, deficient 230Th dating have been
Studies 011. the Dating Metlwds for QHatern.a1コISamPles 39
T乱ble1 List of Coral Samp!es
Code Sample I Eleva-出向 |NherjQographlcUni川叫 Sample Loc山 13 Species
CU 1 I 60-12-9 I R官cent(1ived) I - 25m I Between Naka-bishi and I Favia I Uku-bishi, Kume steciosa
CU 2 1示三 吋 Cora可証下一瓦市iムス孟一一一一一[孟示arustica
Rais邑dCoral Reef 2m W. of Araki, S. Kikai CK 2 I 65-12-22-1-2 Rais己dCoral Reef 3,....,41n Komiya, S. of shrine, I~山f1仰
Shiomichi, C. Kikai retiformis
CK 3 1 65--12-24-6-2 Raised Coral Reef 4~5m I SWW. of Nak呂zato,羽T.Kiaki
CK 4 I 66-5-10-2-1 I Araki Limestones 27m I 150m NW. of Araki, S. I Kikai
CK 5 I 65-12-23-6-2 I Upper Limestone 43m I 750m N. of Kamikatetsn, I ilca押thastr,仰Member I S. Kikai echi向。ta
CK 6 I 65--12-23-6-1 I Upper Limestone Member
CK 7 I 64-7-20b Upp巴rLimestone Member
CK 8 I 66-5-12-3 I U即位 LimestoneMemb巴r
CK 9 I 65-12司 22-8-4I Upper Limestone I Member
CK 10 I品目山[Older山 one
CK 11 I 66--5-10-14-1 I Top of the Upper I Limestone Member I
CK 12 I 66-5-10-14-2 I Top of th巴 UpperLimestone Member I
CK 13 I 66-5-10-12-1 I Upper Limestone Memb巴r
CO 1 1 64-12--4-5 1 Machinato Limes-tone
1 (N叩 moQnarry) I
43m I 750m. N. of Kamikatetsu, I Favites S. Kikai fi仰 osa
40m I 500m N. of Kamikatetsn, S. Kikai
40m I 500111 N. of Kamikatetsu, S. Kikai
50m I 500m NW. of Shiomishi, C.Kikai
150m I 750m E. of Shiramidzu, I Favia iC. KikaI magnistella
18m I 700111 SW. of Nakazato, W. Kikai
18m I 750m SW. of Nakazato, 羽T.Kikai
28m I 800m N. of Araki, W. Kikai
Table 2 List of Tridacna Samole
Code I Eleva帽 1N削除rI Geographic Uni1 ~'~'Ution I Sa町 1e1>ocations
TM 1 I Recent (lived) Om I Drift on beach, Ogami-jim呂
TG 1 I R日cenomI Drift 0n b巴ach,Miyagi-jima
TK 1 I Recent 2m I Colle氾tedin Raised Coral Reefs, W. of Araki, S.Kikai
T 1 1 I Yanoshita Limestone I high tide i Yanoshita寸ima
TO 1 I Yontan Limestone (Sobe Quarry) I I Nakagami, Okinawa-jima
TU 1 I Ohara Limestone 40m I Kitahara, W. Kume
T M 2 I Irabu Limestone 4m I Kogan印刷isaki,1.2Km NVv of I Hisamatsu, C. Miyako
40 Kazuhisa KOMURA and Masanobu SAKANOUE
sample having diameter of 18 cm near the root was collected in the
cav色 atIke-jima very ne品rby Okinawa-jima. Surface of it is brown and cocεntric
many rings are observed in cross section of the sample.
1'he wat色rsw巴resampled at the following places: cave “Yuhiヘmouthof Taibo
River and Shioya Bay づima)乱ndTsukumo (Noto陶 Peninsula)。
V旬 AnalyticalProcedures
v寸 SampleDecomposition
Except for several sampl記s,sample blocks of about 20-40 grams w日recarefully
selected from the sample of coral and Tridacna shell still in aragonitic structure and
were dissolved in 200~300 ml of 6N HN03 + O. 05N HF mixed acid in a 500 ml
beaker二1'hetracεr solutions of 234Th, 233Pa and 232U may
contain small amount of 2281'h and its daughter nuclides in the course of storing)
w邑readded to the sample solution to know the chemical in the and
The solution was th巴日 heatεd undεT an infra r日diamp and
left for several d品ysto attain the isotopic between tracer and
the in sample. If this solution contained significant amounts of undissolved
matter, then it was filtered off by passing through a filter paper Toyo Roshi
Ltd.), and the residue was decomposed with the filtεr paper, initiaHy
hεating with conc. H2SO品 andthereafter with conc. HCI04十 conc.HN03. The
resultant s01ution was to taken in 8NHCいO.lNHF mixture and
put together with the solution.
In the case of stalagmi t<色 sample,about 100 grams of blockεs was taken
and decomposed in the same manner as the case of coral samples,恥causeof its very
low uranium oontεnt and of the exsistenc宕 ofphosphate ion that interfere the recovery
of the thorium isotopes.
v -2 Initial Concentration of Radioactive Elements with Hydroxide Precipitation
After an attainment of the isotopic exchange equilibrium, th巴 solutlonwas trans-
ferred to conical beaker made of glass, and boiled to expel dissolved carbonate ions
in the solution and the hydroxide of iron was precipitated passing ammonia gas
free from COz. As the high ionic str色 ofthe solution makes the efficiency of
the copr邑cipitationworse, especially the coprecipitation yi色ldof uranium isotopεs,
bioled water was added to dilute the solution, and large excess of ammonia gas was
blowεd into th色 solutionfor the sake of bεtter coprecipitation of the trace elements.
1'he hydroxid巴 precipitatecontaining uranium, thorium, protactinium and many
other radioactive decay products was s色paratedby centrifugation in a polyethylεne
centrifuge tub己 andthen dissolved i11 20 ml of 8N HCl solution. The resultant solu同
tion which contains organic matter and small amount of calcium ion as well拠出合
radioactive elem開 ts,was transfεrred to the conical b悶 kerused previously for the
8tudies on th8 Dating lVfethods for Quatornary Sal1ψles LH
initial hydroxide precipitation, and evaporated to dryness on the hot plate. About 5
rnl of conc. H2S04 w乱sadded to the residue and heating was continuecl to conv色rtaIl
the s必tsto sulfate until the white fume of S03 ceased to come out. If the blackish
thick rnatter註ppeareclcluring the heating, heating was suspended and then O 1111 of
conc. HCI04 and conc. HN03 were added careful1y along with 出合研rallof the bε呂ker,
and the heating was resumεcl to clecompose the organic ll1atter until the solution dried
up. The residue was dissolved in呂bout150 1111 of dilute HCl by boiling the solution
long tim邑. If thεinsoluble mattεr still remain己din the solution, the suspended matter
was filt色redoff passing the solution through the filter paper (No 5C) and washed
sufficient1y ¥円th8NHCl卜o.1NHF solution. This residue was usually discarcled, b← cause the quantity of the radioactive elell1ents adsorbed on t11巴 fi1terpaper was neg同
ligibly small excεpt in t11色 caseof dealing with stalagmite sample.
In the case of stalagmite sample, thorium isotopes werεadsorbed strongly to the
unclissolved residue, therefOl占ふ carbonate fusion was carriεd out to cl日composethe
resiclue completely. Aftεr cooling the fusion products, it was tak巴nup with 3NHCl
and呂dd色dto the original solution.
Th巴 solutionthus processecl w品s boiled and the hyclroxide precipitation was
repeated twice and finally washed with the boiled water containing ammonia gas to
remove chloride ion.
All the proceclures were controlled by means of gamma countings.
V ・3 Initial Separation of Raclium, Thorium, Protactiniul11 and Uraniul11 by Anion
Exchange Method
The hydroxicle precipitate thus obtained was clissolved in O. 5M I-hC204 solution
as smal1 quantity as possiblε(usually about 5 1l11), and the resultant solution of
yellovvish gr巴encol.oured was passed through an oxalate form anion exchange column
(41), which retains uranium, thorium, protactinium, iron and polonium and pennits
radium, actinium, lead and alkaline巳arthelements to pass through. After washing
the column with 5 column
volumes of O. 5Jl!f H2C20品
solution, thorium, protac-
tinium, and uraniu111 wer巴
eluted stepwisely from the
column by passing 6 column
volull1es of 8N HCl, 4 coト
umn volumes of 8N HCl-:
o .1N HF and finally 10
column volumes of 6N HCl
イlNHCI04 mixture. Elu-
tion diagram of these proce句
dures is shown in Fig. 13,
Ra Pa U
一Cコ
7 12 16 23
I Unit in Free Column Volume)
Fig. 13 Elution Diagram of Ra, Th, Pa, U and Fe from Anion Exchange R巴sinColumn
42 Kazuhisa KO!VlURA and Masanobu SAKANOUE
which was obt乱inedby a model experim色ntusing the radioactive tracer of
233Pa, 237U and 59Fe.
In thξfirst step of thorium an yellowish green band of oxalate complex
of iron (III), [Fe(CZ04,)3]3-, is converted to brown chloride complex and the iron
band expands twice thεinitial width. Though widening of iron band occurs also in
the last step of uranium巴lution,elution of iron does not take place. If the hydroxide
PIでcipitatewas dissolved in 8N HCl solution, because of the exsistence of impurities
that could not be dissolved in oxalic acid solution, the column operation was begun
from the step 01 thor.ium elution.
All th己 procedureswerecontrolled by gamma countings and gamma spectrometry
of each fractiono Dεtection of the mutual contamin拭 ionor thorium and protactinium
is possible means of g乱mmaspectrometry even in the case of 300: 1 and 1 : 4 in
bet乳 activityratios betweεn them (42).
Although the ch己micalbεhaviours of polonium in the anion exchang色 pr目。cedur色
was not studied in detail, preliminary experiments indicated that polonium would be
still retained on the anion E己sm with the carrier smce po凶
lonium could not bεfound in品nyfraction oI eluate. If this expεctation is corrεct,
polonium will be recovered from the column separately from iron the fractional
elution using appropriate conc巴ntrationof nitric acid.
Packing( Polyethyl告ne)
Holder (8r口55)
Fig, 14 Electrod邑positionCe!l
Each fraction thus obtained were sub国
mitted to the final purification from the
interf邑rringelements Ior the electrode回
position process by, m巴ans of cation
exchange or solvent extraction tech由
mques.
V-4 Purification and Electrod巴
of Thorium Isotones
The thorium fraction which contains
oxalic acid driven out by hydrochloric
acid and small quantity of ca1cium, was
transferred to 50 ml beaker and treated
with conc. HN03ートconc.HCI04 solution
to decompose oxalic acid. White residue
containing calcium salt was taken up
with 5 ml of 3N HCl solution and passed through a cation exchange column (43)
(H-form) .which adsorbs selectively thorium, and other impurities pass through this
column. Thorium was eluted from the column with 10 ml of 0.5λ;J HZC20品 solution.
Oxalic acid in thorium f問 ctionwas decomposed by h色atingwith conc. HCI04+conc.
HNOa mixture as befor巴, and thεsolution was evaporated to dryness.
Slzdies on the Dating 1VI ethods for Quaternary S骨 nρles 43
Radiochemically puri:fied thorium was taken up v,ァith5 1111 of O. 5N HCl solution
by heating ca!川 lyon th,~ hot plate, and th己n 1 m1 of 0.5β![ J-hC20恥 4m1of 4N
NaCl and 0.8 ml of 2N HCOONH生 solutionswere added (44). The solution thus
prepared was transferred to a poly巴thylene 色lectrodepositioncell ((3 cm height of
polyethylene tubing with out-side diamet色rof a. 4 cm ancl insicle d iamet巴r01' 2.8
cm). A stainless steel disc ha ving cliameter of 3. 5 cm serv巴das the cathod, wh巴reas
a platinum wire as an 司node. The v己rticals己ctionof the electrodeposition cell is
illustrated in Fig. 14. Thorium was electrodeposited for 2~-, 3 hours at ccnstant cuト
r巴ntof 0.5 A. After an electrodeposition司 stainlesssteel cathocle was rinsed suffici崎
ently with distil1ed water, and clried under an infra red lamp. The electrodepositecl
plate was counted under a 2'1 encl叫日パnclowtype GM tube to determine the chenlical
yield of thorium isotopes. Th邑 overallchemical yield variecl from 10 to 85 per cent
(m色anvalue 45匁;).
V悶[5 Pllrification and EIectn
Pllrification 01" protactil1iul11 was carried out by a solvel1t extraction technique
l!sing DIBK-HCl system (45). To the protactinium fraction obtained by al1 anion
exchange procedur巴, 2 m1 of AICh saturated solution in 8N HCl was acldecl to mask
the fluoridεion, and protactinium was extracted with 4 m1 of DIBK by shaking
vigorously for 2 minut己s. After the cεntrifugation, an urganic phase was transferrεd
to another polyethylen日 tube,and th己 extractionwith 4 and 2 m1 of DIBK were
rep色ateclto assur巴 thecompletE‘ transfer of protactinium to organic phase. Protac同
tinium in organic phasεvvas washed ¥llith 4 m1 of 8ムrHCl and finally stripped to
aqueous phase with 4 ml of O. 5N HCl solution.
An electrodepositivn of protactinium fractiol1 was carried out by entirely the same
manner as th巴 C呂S色 ofthorium, Il1 ch己micalcomposition of electrolyt巴sand also
in conditions of electrodeposition, inst巴aclof the m巴thodrecommencled before (46).
Overall chemical yields of protactinium varied from 10 to 75 per cent (rnean value
4096).
v -8 Purification and Electrodeposition of Uranium Isotopes
The uranium fraction usually clid not need the further purification. However, in
the叩 sethat the amount of the residu巴 afterthe evaporation of the uranium fractiol1
was consicler旦blylarge, solvent ext日 ctionp1'o田 durewas carried out by using the
T10A時日Clsys民111as follows. The r己siduewas dissolved in 5 ml of 8N HCl solu-
tion and uranium was extracted with 3 ml of TIOA. Extraction was repeatecl twice
with 3 ml of TIOA and the uranium in organic phase was washed several times with
8N HCl solutiυll. Finally uranium was back extracted to aqueous phase with 5 ml 01
o .1N HCl solution and the solution was evaporated to clryn巴sswith conc. H2SOι-
conc. HN03 to decompose any organic matter mixed with.
44 I王azuhisaKOMURA and Masanobu SAKANOUE
一一よ竺39出
回目 cenfrifuge)
(… (wt同
a
-延
長-C, HC10l, ., C トIN03
(evap, )
イ-3N HCI v
t iOi7
(washing)
↓3N HCl
( e!ution)
I Q,5M H2C204
ITh I i←C, HC104 ←C, HN03
(evap, )
↓ (Elecfrodep.l
c
(Anion
持勢
!←AICI3(sCltd, in 8N HC1)
!← DIBK ( shake)
r-8N HC! )( 2
I 0,5N HCI
摂 自由
(Elecfrod牢
Fig. 15 Analytical Scherne of the Carbon岨teSarnple
exchan,CJe J
イ;ご世会3, 8上!HC1" Q,lN HF
t由州
4, 6,ti HC1,. lN l:iCLQ且唱団側持
b
持紅
白恥ーよ…
IOA
10rg.1
~
F也由 e
Studies on the Dating Alethods for Qz.atcrnar:v Samtles 45
The uranium thus purifiεd was taken up wlth 2 ml of 2N HCIO;t undεr the
h己ating,and 2.5 ml of 2lYI Hcoor可H,;, ω!utionand 10 ml of distilled ¥'1旦tcr-¥.:vere
add己dto make up th色合lectrolyticsolution, instead of the method配 velopecl Hashi四
moto and Sakanou日 (47). The solution thus p了色paredwas transferred lnc.o the elεC岨
trodεposition cell叩 duranium was electrod己 ona stainless st出 platεfo1'
about .3 hou1's at a constant current of 0.4 A. Ov邑rallchemical yield oI l11・ani.un
isotopes varied f1'om 20 to 70 per cent (mean value め.
All the purification methods clescribed above are shown schematicaIly :in 15.
VI MeaiJUl'elrUe11的
Chemical yields of thorium and protactinium isotopes through a11 the proc日dur巴
including the coprεcipitation, anion exchange多 purificationand electrodeposition w邑re
determined by beta countings using a 2'/ enふwindowtype GM counter, whereas that
of uranium was determined by m日ansof sptctrometry. Alpha spectrometr.ies
wer巴 carriedout by using Double Gidded Ionization Chamber (48) with very io¥v
back ground activity and with high counting efficiency. In Fig. 16, the apparatm;
used for alpha spectrom巴tryis shown. Enεrgy resolution of this chambεr was mεas同
* Alpha Spectrometric Analysis Using 232U as Uranium Tracer 料 FJ.uorim.etricAnalysis by Ohashi, Atomic Fue! Co.
料*: Activation Analysis by Osawa and A加, Kanazawa Univ. 料*ド UraniumContents of Recrystallized Part (Ca!cite Part)
As kn::Jwn from this table, the results of alpha spectrom巴tricanalysis agree quite
wε11 with that of fluorimetry except the case of TM 2. This fact indicates the
of the alpha method using 232U as uranium tracer. It is
also known from this table including the results of activation analysis that the
ur拠出m concentration in a Tridacna shell is f品rfrom homogeneity even if the blocks
were taken from the very near part in the same sal11ple. This fact gives an interεst-
biological problem as to the mechanism of th己 traceelement introduction in a
shell. Though th巴 alphasp巴ctrometricanalysis cannot discuss the detailed variety of
the uraniunユ concentrationin l11icro scale b巴causeof its low sensitivity (at least
several microgram of uraniul11 is needed), it is evident that the distribution oI urani働
um in a shell is heterogeneous also in fairly macro scale.
In this r色spect,a very interesting study was reported rec色ntlyby Lahoud et al.
. They the uranium distribution in the shell sal11ples collected from
variousεnvironment (fr色shwater, brackish and marine), by using newly developed
teclmique of fission track methodヲ呂ndobtained some interesting regularities about
the uranium content and distribution: (i) ur品niumconcentration in molluscan shell
differs conspicuously by the environment of the mollusc dwelling, (ii) ur・anium
concentration in a shell differs very widely the position of the same sample, i.e.
巴xternalvalve surface contains more uranium than internal valve surface, and the
fructured surface contains by far little amount of uranium than extemal and internal
valve surfaces.
Studies開 theDating Jii[ethods for QuatemaηS印刷es 49
It is wε11 lmovm that the migration of the trace e1ements may occur during the
change of crystal structure. In th巴 caseof fossil carbonate samples, this will be
recognizecl as the change from th己 metastab1earagonite to stable calcite Iorm. The
results of TM 2 and TU 1 indicate th邑 enrichm己ntof uranium at the tim日 ofrecrvs四
tal1ization, that is, calcite part contains more ur乱niumthan aragonitic par仁
As sugg巴sted alreacly abov巴 itmust be emphasized that the study of the
clistribution of the trace elements in micro scale is veIγimportant to recognize the
correlation between biologica1 action and the trace e1ements introduction during the
growth or after the death of organisl11s. Activation analysis, fission track techniqu日
and the activation autoracliography, which is cleveloped by Sakanoue et a1. (50), seem
very promissing to inv巴stigatethe clistribution of the trace elem色ntsin very small
scale, because of their high sensiti.vities and/or easiness for perfonnance.
Besicles the diffrences of the uranium distribution in a shell, the variety of
uranium content among th巴呂amespecies of mollusca must be pointecl out. It 1S very
interesting that the uranium content in Trulacna shε11 tends to incr巴asefrom geo-
logically younger sample (TM 1, 0.04 ppm) to olcler one (TM 2, 1.21 ppm). Similar
results have b巴enreported by Blanchard (51) and Stearns et a1. (28) for uranium
and by Lowenstam (52) for strontium in fossil molluscs. These facts may be ex司
plainecl by assuming that some traceεlements are intr吋 ucednot at the time dur加 g
the grQwth of th芭 organisms,but at the time oI degradation of the organic m呂tter
in their structures.
vn帽 2AnalyticaJ Results of Coral Samples
Analytical results giv邑nin Figs. 20, 21 and 24 are expressed as the activity ratios of 234U /238U, 230Thj234U (労巴quil.)and 231Paj235U(タbequilふ Here,the activity ratio 231Paj235U was calcu!ated from the activity ratio of 231Paj238U by呂ssumingthe activity ratio of 235U 知 238Uas 1 :21. 7. 1n the right hand two columns, the ages calculated from 230Thj234U and 231Paj235U ratios ar官邸時n,although these data are 110t sulヲmittedto any correction as to initial 230Th aud 231Pa as discussed below。Analytical resnlts of different blocks of the same sample afe distinguished by the subscript a, b and c.
Fig. 20 shows the analytical results of coral samples. All the samples lis民d
above CK 10 are remained still in a悶 goniticstructure. As known from this figure,
231Pa ages show considerably good agreεment with the ages of 230Th method, and
the 234U/238U ratios do not contradict to their initial ratios of 1. 15~ 1. 14 recognized
as their ratio in sea water. Particular1y, the sample having the ages of 40~70
thousand years (CK 4, CK 8, CK 5 and CK 13) give completely the same ages
betwe巴nthese two indepεncl色ntmethocls within the statistical errors, and other inde-
pendεnt method using 231Pa/230Th can a1so be applied by assuming the initial 234UI
238U ratio as 1.15.
However, 231Pa methocl seems to give systematically somewhat olcler ages than
230Th method for relativεly younger samples of less than ten thousand years, for
50 Kazuhisa KOMURA and Mas旦nobuSAKANOUE
Ages (1i 〉くP1a0-E231 y) Th-230 1 Pa-231
2.85島一'.3エ 0.'
methodl method
CU1 I.5士0,2 7.4士,.5 同 (1.6::1::0.2) ( 3ωヰ
CU2 3. 12 暗 J. 3:t 0-" 最I/Ji
a 2呂6 臨 ト唱:;}4 5.9士0.3 ,8土3 関 6.6土 0.3 9.4士2.0CK 1~ 2.74 醐 O よ2 土0.' 16+ I t,'i< 5.8土 0.2 8.1土0.6
Mouth of Taii:Jむ Riv.(Okinawa) 2 .20~ 0.70 U7士0.03
Shioya Bay ( )) 2.86士0.71 7J8Io.白
Tsu!,umo 8(.'1)1 (Noto防 n.l 3.2土 0..7 UI, I003 I 寸
Fig. 24 Analytical Results of Sta!agmite and Water Samples
Stlldiesοn tJze Dating iiJethods f01~ Quaternary Sω}ltles 57
Ground wat色rof cave“Yuhi' and s色V記ralcoastal sea ¥vater of Okinawa and Noto
Peninsula w邑realso analyzed f.yr their uranium con七色ntand r品tios. As
known from Fig. 22胃 cavewater・samplesgive considerably large amounts of uranium
(2.3 microgramiliter) and high 2'l4U p38U r丘tioof し 33~1. :34. Since the
source of uranium in cave water sample is considεred to be the 1i mes torぬ bed,tlll"ough
which t11色 groundwater has pas2εd, high 23生U/23呂lJratio ¥7/i11 "be cauE;eci bv the
preferential leaching of daughter nudide 23,t U with parent 238U, because
the :!3'~UÎ238U ratio in the ]imestone b吋 cor:npos釘 ofmarine depo~ヨited calcium
carbonates is considered to ha vεat 1110St the Sanl己 vaJueof sea water (1圃
The preferential leaching oi nuclide may be due to thεr巴coi1 E f.fect of
alpha ancl beta decay processes, which makεS 234U moreεachable than parent 238U,
as旦ssumedfirstly by Cherclyntsev (1 j) to explain the anomalous ratio in
natural uranium 巴S.
Three samples of co乳stalsea water the activity ratios of 234U(l38U 1.17と
0.03. 1.18土0.03and 1.14士O.OB.These vahws do not contradlct to th巴 clatareported
by many authors (13,
VIU Discl1ssions on the Causes of El"l'Ol'
Errors expected to be brought into this dating method are classiiied into following four groups. Those品1・e(i) pipetting error or the unc巴τtaintyof the concentratiol1 of 232U spiked, (ii) i111purities in the tracer solution, (iii) col1nting statistics and (iv) contamination or the sample with foreign materials. Those fadors are discnssed below.
VIH-1 PipeUing Erro1' and the Absolutθ of 2112U
Pip日ttingof thorium and protactinium tracer was carriecl out thεultra
M S呂ckett,W.M. and Potratz, H.A., Subsurface geology of Eniw邑tokatoll, Dating of carbonate
rocks by ionium and uranium ratios, USGS Profess. Paper 260-BB (1963). 伸 Bro色cker,Wふ, A preliminary evaJuation of uranium serIes ineql日ilibriumas a tool for absoJute
同 Blanchard,R.L吋 Uraniumseries disequilibrium in age determination of marine calcium caト
bonates, Ph. D thesis, Wおhi時 tonUniv吋St.Louis, Mo. (1963). 同 Cherdyntsev,V.V., Kazachevsky, LV. and Kuzmina, E.A., Isotopic composition of uranium
and thorium in superg邑nezone. Studies on the
Studiesωz the Dating }¥{ elhods for QwIter持arySarntles 65
4骨 Cコhe釘r釘吋ピdyntsev,V
foωrn日ma討tionby isotopes of thoぽriu町1mand uran凶ium,Geokhimiya (1965) 1085. 。0) Alokseev, V.A., Kazachevsky, I.V. and Cherdyntsevヲ V.V.,Izd. Akad. Nauk SSSR, Absolute geochronology of Quaternary period (1964).
凶 Cherdyntsev,V.V., Malyshev, V.I. and Kazachevsky, I.V., Isotopic composition of uranium and thorium il1 supergene zone. Study of peat bog substances, Geokhimiya (1964) 399.
eql1ilibril1m uraniClm in carbonate deposits and their age determination, Geokhimiya (1966) 139. (23) Titaeva, N.A., On the possibility of the absolute age det巴rmination()f organic sediments by
the ionium method, Geokhimiya (1966) 1183. 自4) Kaufman, A. and Broecker, W.S., Comparison of 230Th and 14C旦gesfor carbonate materials
from lakes Lahontan and Bonneville, J. Geophys, Res. 70 4039 (1965). (2日 Thl1rber,D.L., Broecker, W.S・, Potratz, H.A. and Blanchard, R.L吋 Oraniumseries ages of
Pacific atoll coral, Science 149 55 (1965). (2目 Broecker,W.S. and Thl1rber, D.L., Uranil1m series dating of corals and oolites from Bahaman
and Florida Key limestones, Scienc巴 14958 (1965).
ロ百 Osmond, J.K., Carpenter, J.P. and Windom, H.L., 230Th/234U ages of the Pleistocene corals
and oolites of Florida, J. Geophys. Res. 70 1843 (1965ト白日 8tearns, C.E. and Thurber, D.L., 230Th/234U dates of late Pleistocene marine fossils from
the Mediterranean and Moroccan littorals, Quaternaria 7 29 (1965).
凶 Richards,H.G. ancl Thurber, D.L., Pleistocene age cletermination from California and Oregon, Science 152 1091 (1966).
側 Veeh,H.H., 230Th(238U and 234U /238U ages of Pleistocene high sea level sta吋, ]. Geophys.
Res. 71 3379 (1966ト(31) Fanale, F. and Shaeffer, 0., The heril1m幽uranil1m ratios for Pleistocene and Tertiary fossil
aragonites, Science 149 312 (1965). 問 8haeffer,O.A. and Davis, R., 36Cl in nature, New York Acad. Sci. Ann. 62 105 (1955). 。3) Rightmire, R.A., Kohman, T.Pψand Hinterb巴rger,H., Cマberdie Halt制wertzeitcles langlebigen
26Al, Z. Naturforschung 13a 847 (1958). (胡 Merrill,J.R., Lyclen, E.F.X.,日onda,M. and Arnold, J.R., The sedimentary geochemistry of
(36) Sackett, Wふ1.,Protactinium-231 content of ocean wat
66 Kazuhisa KOMURA and Masanobu SAKANOUE
品目i) Sakanoue, M., Takagi, T. and Maeda, M., Studies of the adsorption and electrodeposition of
protactinium, R且diochimicaActa 5 607 (1966).
間 Hashimoto,T. and Sakanoue, M., Basic studies on the production of enriched uranium-237 and the measurement of its specific activity, Sci. Rept. Kanazawa Univ. 11 49 (1966).
(4日 Doke,T., A new m巴thodfor the reduction of alpha-ray background in a gridded ionization
chamber, Can. J. Phys. 40 607 (1962). 帥 Lahoud,J.A., Mi11er, D.S. and Friedman, G.M., Relationship between depositional environment
and uranium concentration of molluscan shells, J. Sed. Petro1. 36 541 (1966).
間1) Sakanoue, M., Konishi, K. and Komura, K., Stepwise determination of thorium, protactinium and uranium isotopes and their application for geochronological studies, IAEA symposium on Radioactive Dating and Methods of Low-level Counting at Monaco, SM 87/28 (1967).
(51) Blanchard, L., Relationship between uranium and radium in coastal marine shells and their
environmcont, J. Geophys. Res. 70 2911 (1965).
師団 Lowenstam, H.A., “Sr ICa ratio of skele句1aragc>nites from the recent marine biota at palau
and from fossi1 GastropodsヘIsotopicand Cosmic Chemistry (Craig, H., Miller, S.L. and Wasserburg, G.Jふ NorthHolland Pub, Co., Amsterdam, 114 (1964).
(臼i) Moore, W.S. and Sackett, W.M., Uranium and thorium series inequi1ibrium in sea water, J. Geophys. Res. 69 5401 (1964).
倒 Kuznetsov,Yu. V., Simonyak, Z.N., Eleizarova, A.N. and Lisitsin, A.P., Content of protac-tinium and thorium isotopes in ocean water, Radiokhimiya 8 455 (1966).
日,) Mii, H. and Kigoshi, K., Radiocarbon dating of the ancient beach and coastal dune deposits, Kikai Island, Amami. 14C age of Quaternary deposits in Japan XXXVIII, Earth Sci. 82 43 (1966) .
臨時 Blanchard, R.L., 234U 1238U ratio in coastal marine waters and calcium carbonates, J. Geo-
phys. Res. 70 4055 (1965).
(57) Koide, M, and Goldberg, E.D.,“Uranium-234/uranium-238 ratios in sea water", Progress in
Oceanography vo1. 3 (Sears, Mふ Pergamon,London, 173 (1965). 側 Umemoto,S., 234U 1238U in sea water from Kuroshio region, J. Geophys. Res. 70 5326 (1965).
捌 Miyake,Y., Sugimura, Y. and Uchida, T., Ratio 234U 1238U and the uranium concentration
in sea water in the western north Pacific, J. Geophys. Res. 71 3083 (1966).
(印1) Sakanoue, M. and Komura, K., The preparation of carrier-free U-232 and the estimation of