Asayama, Tetsuji

Hatuda, Zinitiro

Nishimura, Susumu

English

Kyoto University Research Information Repository

RIGHT:URL:CITATION:AUTHOR(S):ISSUE DATE:TITLE:A Trial Method of DeterminingUranium and Thorium Content ofRocks in Radioactive Disequilibriumby Neutron Activation Analysis (2)Hatuda, Zinitiro; Nishimura, Susumu; Asayama,TetsujiHatuda, Zinitiro ...[et al]. A Trial Method of Determining Uranium and Thorium Content ofRocks in Radioactive Disequilibrium by Neutron Activation Analysis (2). Memoirs of theCollege of Science, University of Kyoto. Series B 1967, 33(4): 221-2261967-03-20http://hdl.handle.net/2433/258339MEMolRs oF THE CoLLEaE oF SclENcE, UNwERslTy oF KyoTo, SERms B, Vol. XXXIII, No. 4 Geology and Mineralogy, Artic}e 2, !967A Trial Method of Determining Uranium and Thorium    Content of Rocks in Radioactive Disequilibrium           by Neutron Activation Analysis (2)ByZin'itir6 HATUDA, Susumu NISHIMURA* and Tetsuji ASAYAMA*Geological and )iv[ineralQgical Institute, University of Kyoto             (Received Dec. 15, 1966)                                Abstract   In the first paper was reported the uranium and thorium content of some basic lavas de-termined by using neutron activation method. Additional data are presented in this paper. Asthe result, it seems that Th/U ratio of basaltic lava of historical age is higher than that of andesiticone, and that the radiurn content of tholeiite lava is approximate to the equilibrium quantitywith its uranium, while that of alkali olivine basalt Iava highly excessive.                              Introduction    Most of the data of uranium content of rocks hitherto appeared are those           Åë'deduced from radium content determined on the assumptioR that uranium andthorium are in radioactive equilibrium. For the rocks younger than the timerequired for establishment of radioactive equilibrium, it is obviously not proper tomake such an assumption, because during differentiation and consolidation of themagma, uranium and radium wi}1 behave differently according to their chemicalproperties. Moreover, re-fuslon and assimilation wi}I cause a loss of balance be-tween uranium and radium.    The final aim of the present investigation is to obtain data of content of ra-dioactive eiements in rocks useful for estimation of heat fiow in the crust, but itseems that some interesting petrological or geological problems exist in connectionwith disequilibrium of radioelements, especially in basic effusive rocks.    In the first paper'), some results on lavas from Sakurajima, Kirishima, Aso andHakone were presented. In this paper, newly obtained uranium and thoriumcontent of basic lavas from other localities, and as a reference, radium content of* Department of Geological Sciences, University of Osaka Prefecture.222 Zin'itir6 HATuDA, Susumu NismMuRA and Tetsuji AsAyAMAlavas hitherto obtained by other authors are summarized. Of the samples used,Hawaii lavas were those kindly offered by Prof. N. IKEBE of The Osaka CityUniversity.    The principle and procedure of the determination of uranium and thoriumcontent by utilizing neutron activation analysis were fully described in the firstpaperi) and therefore, omitted here.                      Brief netes on the samples    The samples used in the present study are listed in Tabie 1. They are mostlyFig. I.0           o 2km           _Sampling sites in Izu-Ohshima: the numerals associated withsample numbers show the times of eruption of the lava con-cemed.A Trial Method of Determining Uranium and Thorium Content of Rocks 223Table 1. Samples used in the uraniurn and thorium determinations.SampleAso ejectaAsama lavaIzu-Ohshima }ava2)   l   2   3Miyakejima lava3)   1   2   3   4   5Hawaii lava  Kilatiea Iki   l   2 Mauna Loa   lTime of eruption  1965  l783  1912  17771550-(1684)  1962  !940  1874  l8351763-l769? historic 1954? historicRock typeandesiteandesite basalt basalt basalt basaltbasaltbasalt basaltbasaltbasaltbasaltbasaltLocalityCentral crater, Aso VolcanoOni-no-oshidashi, Asama VolcanoCentral craterCalderaKomashita-tar6Sanshichi-yamaHyotan-yamaTosaKasajiKuribeLava cascade of Paliokeowe PaliHalemaumauEastern foot of Mauna Loalavas from islands in Pacific Ocean, namely Izu-Ohshima and Miyakejima aboutIOO km and 164 km SWW of Tokyo Haneda Airport respectively and HawaiiIslands. The sampling sites in the former two islands are shown in Fig. 1 and Fig.2, in which the numerals are the times of eruption of the lavas concerned.                      Results and concerning data    In Table 2, uranium and thorium contents determined by using neutron actYvation ana}ysis are listed. On the rocks from Izu-Ohshima, M!yakejima andHawaii Islands, several authors`)5)6)7) have made the radium determinations and theresults are summarized in Table 3. The figures shown under the heading eq. U inTab}e 3 are the values of uranium content calculated from radium content on theassumption of radioactive equillbrium between uranium and radium.    As to the results hitherto obtained, two points may be worth mentioning.  (i) ThiU ratios range from 2.3 to 3.7 for lavas from Sakurajima, Kirishima andAso volcanoes in Kyasya district, and those from Hakone and Asama volcanoes,while most of the lavas from islands, Izu-Ohshima, Miyakejima and probablya!so Hawali, show higher ThlU ratio. Considering that the former group of lavasare andesite and the latter basalt, this tendency nearly corresponds to the resultby EvANs and GooDMAN') that the average ratios for intermediate and basic rocks224 Zin'itir6 HATuDA, Susumu NisHiMuRA and Tetsuji AsAyAMANl64and  4Åí  l835l643?Miyakejimqunknown  agel940l962o 2kmFig. 2. Sampling sites in Miyakejima: the numerals associated with sample numbers      show the times of eruption of the lava concerned.are respectively 2.6 and 4.0. XMhether such a discrepancy is a priori or pesterleri isnot yet decided.  (ii) For the igneous rocks younger than 106 years, it is naturally considered thatthe content of radium is less than the equllibrium amount to uranium, as the RalUratio in equilibrium is about 3.5Å~ 10". As shown in Table 3 of the first reporti),Table 2 and Table 3 in the present paper, andesite Iavas from Kyasya district andmost of the basaltic lavas of Hawaii unexpectediy reveal quite excessive content ofradium.    Assuming that radium determination was correct, and putting aside the samequestion " a Priori or not", there arise a possibility that the radium content of tholei-in Radioactive Disequilib rium by Neutron Activation Anaiysis (2) 225Table2. U ramumand thorium content.SampleAso ejectaAsama lavaIzu-Ohshima 1 (Melji-Taisho }ava)           2 (An'ei lava)           3rvliyakejima l           2           3           tlr           5Hawaii Kilauealkil                 2       Mauna Loa 1U ppm0.80.80.80.70.60.6e.sTh ppm2.31.73.0S.l3.53.12.9Th/U0.50.60.50.40.4(under determination)        2.9        2.9        i.8        2.1        1.22.92.l3.84.45.85.75.15.!4.83.65.2s.oTable 3. Radium content and equilibrium quantity of uranium calculated frorn radium content.SampleIzu-Ohshima Miharayama An'ei lava Miharayama Meiji-Taisho lavaIzu-Ohshirna (average of 5 samples)Miyakejima (average of 4 samp!es)Hawaii Halemaumau l921 Ancient lava, north edge of Kilauea Andesite basalt, Mauna LoaHawaiian basalt*Hawaiian basa}t*RaÅ~!0-i2 glgO.IOO.!30.120.120.940.940.94!.25O.!5eq. U ppm0.290.380.350.352.82.82.84.30.51ReferenceKimura and Hamaguchi4)       tr       lrIwasaki5)PiggotG)       te       1!Jely7)Evans and Goodman7)  * The same }ava sample for intercheck measurement.ite lavas will be normal with respect to uranium content, while that of aikaii olivinebasa}t }avas highly excessive.    The above-mentioned two points are only a suggestion, and in order to get anydefinite conclusion, more data are required. Fortunately, fifteen samples ofHawaiian lava of known lecality and age of eruption have recently become availablethrough the kindness of Dr. Richard S. FisKE of Hawaiian Volcano Observatory,U.S. Geologica} Survey. The activation analysis of uranium and thorium of these}{{awaiian samples are now under way and also radium determination of the sameand rocks from Izu-Ohshima and Miyakejima are in preparation.226l)2)3)4)5)6)7)          7..in'itir6 HATvDA, Susumu NisHiMuRA and Tetstlji AsAyAMA                             ReferencesHATuDA, Z., S. NisHiMvRA and T. AsAyAMA (l966): Menz. Cot{. Sci., Univ. Kyoto, 33,   47-5i.NAKAMuRA, K. (i964): Bull. Earthg. Res. Inst. JaPan, 42, 685.IssHiKi, N. (1960): `MiyAKE-JiMA' Explanatory Text of lf50,000 Geologic Map of Japan    (Geol. Surv. Japan).SvwA, A. (1965): Explosing Japanese Islands, Blue Backs No. 28, K6dansha, Tokyo (in   Japanese).KiMuRA, K. and H. HAMAGuam <1943): Jeur. Chem. Soc. jaPan, 64, 125-128 (in Japanese).IwAsAKi, I. (1943): The Summary Report of the Lectures at the 65th Annual Meeting of   Chem. Soc. Japan (in Japanese).PiGGoT, C.S. (1931): Amer. Jour. Sci., Sen 5, 22, 1-8.EvANs, R.D. and C. GooDMAN (194i): BuU. Geot. Sec. Amer., 52, 459490.

A Trial Method of Determining Uranium and Thorium Content of Rocks in Radioactive Disequilibrium by Neutron Activation Analysis (2)

RIGHT:URL:CITATION:AUTHOR(S):ISSUE DATE:TITLE:A Trial Method of DeterminingUranium and Thorium Content ofRocks in Radioactive Disequilibriumby Neutron Activation Analysis (1)Hatuda, Zinitiro; Nishimura, Susumu; Asayama,TetsujiHatuda, Zinitiro ...[et al]. A Trial Method of Determining Uranium and Thorium Content ofRocks in Radioactive Disequilibrium by Neutron Activation Analysis (1). Memoirs of theCollege of Science, University of Kyoto. Series B 1966, 33(2): 47-511966-11-15http://hdl.handle.net/2433/258326INtlEMoms oF 'r}iE CoLLEon oi" SciENeE, UNivEizsi'ry oF Kyo'ro, SwwiEs B,   Vol. x}<XiXIII, No. 2 Geology arid l ineralogy, Article l, 1966A Trial Method of DetermiRing Uranium and Thorium  Content of Rocks in Radioactive Disequilibrium by             NeutroR Activation ARalysis (l)ByZin'itiro IIATUDA, Susumu NISHIMURA* and Tetsuji ASAYAMA*         Geological and INtlineralogical Institute, University of Kyoto                      (Received june SO, 1966)                               Abstract   rl'he uraniLun and thoriuni content of some basic lavas has been deterinined by using theneLttren activation met}iod. These lavas revealed raclioactive disequilibrium by means of alpha-and gamma-ray spectra interpretation. The uranium content of some lavas in younger his-torical ages has beeii feund te be smaller than that calculated from their radium content assumingthe raclioactive equilibrium, while their ThfU ratios are in average value for such rocks.                           1. Introduction    rl"he uranium and thorium content of rocks and meteorites has been determinedby a few workers by neutron activation analysis. This method is believed to beeffective for the determination of uranlum and thorium at the sub-microgram levelin basic rocks and meteorites')t2),3).    Usually the direct radiometric method is used'i)'5)'6) on the assumption thatthe samples are in i-adioactive eguilibrium, but it is noteworthy that not a fewsamples of rocks in nature are in radioactive disequilibrium. Among them arelavas presumably suffered from various geochemical processes.    The radioactive disequilibrium feature of the sample with high content ofuranium and thorium is easily found by the alpha- and gamma-rays spectrometry,while that of the samp}e with low content of them as rocks will not be so. In thelatter case, the deteriinination of uyaniuin requires other methods. The authorshave adopted the method in which tl}e rock samples are first activated by theneutron bombardmeRt and subjected to the spectrometry after an optimum periodof cooling during which most of the produced short-lived nuclides are decayed * Department of Geological Sciences, University of Osaka Prefecture.48 Zin'itiro HATuDA, Susumu NismMuRA and TetsLlji AsAyAMAaway. The irradiation was carried out 2n the hydraulic tubes of the reactor ofthe Research Reactor Institute ef Kyoto Univeysity.    [l]he authors acknowledge the support of the followings in this research: Assist.Prof. S. IwATA and the members of the Research Reactor Institute of KyotoUniversity for the facilities of the irradation and the gamma-ray measurements,and Prof. S. SHiMizu of the Institute for Chemical Research of Kyoto University,for alpha-ray measuremeRts. Finally this investigation has been partly supportedby the financial aids of the Scientific Research Expenditure of the Ministry ofEducation, and of the Co-operated Use of the Research Reactor of Kyoto Univer-sity.2. Nuclear Data   Table 1 lists the relevant nuclear data for the nuc}ides produced byneutron irradiation of the natural isotope mixture of uranium aRd thorium. Table 1.232Th (n, r)238U (n, r)Nuclear data for uranium and thorium233Th -233Pa -233V - .....................239U - 239Np _.> 239Pu _... 235U ww.............slo"rNuclide Haif-life233Th233Pa.233U239U239Np239Pu22.l2 m27.0 d1.65Å~le5y 23.54m2.346 d2.44 Å~ 104 yType of disintegration and its energy (i)vleV)fl-- 1.245r O.e292(2.10/.), O.0869(2.70/,), 0.171(0.70/,)B-- O.l5(370/.), 0.254(580/,), 0.568(5e/.)r 0.301(22*),0.313(150*), 0.341(6*)ct 4.773(i4.99/o), 4.816(83•50/o), 4•717(1•69/o)r o.o42s(o.os o/, ), o.os61(o.ol o/,)fi- l.21r O.o736fi-- O.070(220/,), 0.327(350/,), 0.382(210/,), O.tl,S9(169/.),   0.723(6 0/, )r• 0.1064(50"), 0.2e99(9*), e.2284(28*), 0.2546(0.6*),   0.2777(31*), e.2856(l.4*), 0.3161(3.3*), 0.3344(4.4*)a : 5.e69(IO.70/.), 5.134(16.80/,), 5.l47(72.50/,)* relative intensity                         3. Experimental3.l.I. Desm-i. tion of samp les   The samples used in the present study are }isted in Table 2. They are lavasfrom volcanoes iR Ky(lsha District with one exception of lava from Hakone inKanagawa Prefecture. The Sakurajima lavas are classified according to thetime of eruption: Bummei eruption (1475-6), An'ei eruption (1779), Taish6 erup-tion (l914) and Sh6wa ermption (1946). The magma of ShOwa lava may be the          A Trial Method of Determining Uranium and Thorium Content of Rocksresidual of 'lraish6 lava, consldering from the feature of eruptions and theof the chemical analyses').            Table 2. Samples used in the uranium and thorium determinations49resultsSampleSakurajima  Bummei lava  An'ei lava  Taish6 }ava  Sh6wa lavaKirishima lavaAso lavaHakone iavaTime oferuptlon  1475-6  1779  1914  1946? historic? historic? QuaternaryRock ÅíypeTwo pyroxene andesiteHyperthene andesiteTwo pyroxene andesiteTwo pyroxene andesiteTwo pyrexene andesiteTwo pyroxene andesiteTwo pyroxene andesiteLocalityMochiki, East part of SakurajimaYumoto, East part of SakurajimaAkamizu, West part of SakurajimaKurokami, East part of SakurajimaI6dani SpaCentral craterHakone Pass  3.l.2. PrePae'ation of samptes foT irradiation      The rock is pulverized to the fineness to pass through a 80 mesh sieve. After  having been dried in an oven at l 100C for several kours, it is put into a desiccator  for cooling. 0.2 g of the pulverized rock is put into a silica ampoule, then sealed  at a diminished pressure. The ampoule ls made of silica tubing whose internal diameter is 4 mm, cleaned over night in aqua regia, rinsed several t!mes with  demineralized water and dried in an oven at I100C for three hours.  3.f.3. PrePa?'ation "S s\tt"dexd Sbrc irradiation      The comparison technique is adopted in the present activation anaiysls. In order to minimize the differential effect of neutron self-shielding and fiux enhance- ment, it is desirabie to choose the comparator sampie as rnuch akin as possibie to  the sample to be assayed in chemical composition and physical property. As such  a comparator sarnple (monitor) the Deccan Trap (NBS) (0.7 ppm U, 2.8 ppm Th) is used in this study. 0.2g of this comparator sample is enampouled under a• diminished pressure just the same manner with the sample to be assayed.  3.2. Irradiation conditions      The samp}es and monitor sealed separately in si}ica tubes are placed side by  side in an aluminium container for irradiation. The irradiation is made in the  hydraulic tube of the reactor, in a fiux of thermal neutron of 2 x 10i3 n!cm21sec.  The duration of irradiation is 10 hours.      For the correction of the effect of fast neutron, cadmiam ratio is used,50 in Radioactive Disequilibrium by Neutron Activation Analysis (l)3.3. Gamma-ray sPectTa resotution    The content of 233Pa and 239ATp in irradiated samples is determined by gamma-ray spectrometry about two weeks and two months after irradiation. The gamma-activity ls measured by means of a single thallium-activated sodium iodide crystal,with associated electronic equipment in conjunction with a single channel pulse-height analyser (Aloka, PSM 802, TDC 4) and a 512 multi-channel instrument(RCL). The ability for resolving gamma-ray spectra has basic irnportance for thesuccess of instrui:nental activation analysis. For the resolution graPhicat technique lsused as it is considered to be most appropriate.3.4. Alpha-ra) spectrometry    As a trial, thin source method of alpha-activity measurement was adopted forthe samples from Sakttrajima. To prepare a thin source, both the assayed andmonitor samples were treated with fluoric and nitric acids in a platinum crucibleafter irradiaÅíion, and Åíhen the resultant solution was deposited on a nickel plate byevaporation. To insure the escape of radioelement, gamma-ray spectrornetry wascarried out before and after the chemical treatment, and the correction was rnadeby utillzing S9Fe peak.    The alpha-ray spectrometric assay was made tNvice about a moBth and ninemonths after the irradiation. Al} the samp}es were subjected to the alpha-rayspectrometry as a thick source by means of a 4z proportional flow-counter usingPR gas, the procedure having been fully described by HATuDA and NAGAi8).                     4. Results and Discussiens    The results obtained hitherto are listed in II'able 3. The results for uraniumand thorlum content with thin source were rejected as the number of a}pha particlecounted was insuflricient consideriRg from the statistical point of view. I?or uraniumcontent the va}ues by alpha-ray spectrometry with thick source are cited. Forthe thorium content, the obtained values by alpha- and gamma-ray spectrometrygave the same figures within the experlmental error, differing in the second decimalplace: The figures shown under the heading eq. U are calculated values fromradium content previously determined by one of the authors (T.A.) on the assump-tioR of radioactive equilibrium betweeB uranium and radium.    As shown in the table, ThlU ratio ranges from 2.33 to 3.72 with the averageof 3.1 1, which may be reasonable for basic lavas. So far as the obtained data areconcerned, the radium content of these lavas is highly excessive contrary to theexpectation, as the time elapsed since their eruption is shorter than that requiredfor the radioactive equilibrium between uranium and radium. The discussion               Z"in'itiro HATuDA, Susumu NismMuRAof this problem is }eft for the next report.    Table 3. Uranium and thorium content and equilib            frorn radium contentand Tetsuji AsAyAMArium quantity of uranium calculated51                                                           (ppm)Th (ppm) Sakuraiirna                                                                     3.34•3.0 2.10.9Bummei lava 0.72                                                          IJ           2.7Jr2.2e.sAn'ei lava 0.58                                                                     3.oe1.3             2.l0.7Taisho ]ava 0.46                                                                     3.11Sh6wa lava            o_r)o 1.42.80.9 Kirishima lava 0.7 2.6 0.59 1.7 8.72                                                                     3.jro1.80.611.40.4Aso lava                                                                     2.330.5" 9.lr.geeigy.3 ...... 9•fi ... i.fi. . o.i6     * l!adium content determinecl by T. AsAyAMA7).                                 Referencesl) HAMAGucpn,H.,G.X4i.REEDand A. 'I'vRKEvici-i: Geochim. Cosmochim. Acta, l2, 337-347   (1957).2) MoRGAN, J.W. and J.E. LovERiNG: Geochim. Cosmochim. Acta, 28, 405-417 (l963).3) FiLLEy, R.H.: Geochim. Cosmechim. Acta, 26., 49-51 (1965).4) HuRLEy, P.M.: Bu}1. Geoi. Soc. Am., 67, 395-404 (1956).5) ADAMs, J.A.S.: NTat. Rad. F.nvir., Rice Univ. Semicentennial Pub., 485-497 (l964).6) HATuDA, Z. and S. NisHii uRA: Mem. Coll. Sci., Univ. Kyoto, B, 31, 215-226 (1965).7> AsAyAtsn.K, T.: Mem. Fac. Ind. Arts, Kyoto Tech. Univ., 2-B, 53-69 <195g).8) HATuDA, Z. and J. NAGAr: Mem. Coll. Sci., Univ. I<yoto, B, 28, 527-538 (l962).Sample U ( pm) Ra content* (10-i2glg) eq. U ThlU

A Trial Method of Determining Uranium and Thorium Content of Rocks in Radioactive Disequilibrium by Neutron Activation Analysis (1)

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A Trial Method of Determining Uranium and Thorium Content of Rocks in Radioactive Disequilibrium by Neutron Activation Analysis (2)

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