Hayase, Ichikazu

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RIGHT:URL:CITATION:AUTHOR(S):ISSUE DATE:TITLE:The Radioactivity of Rocks andMinerals Studied with NuclearEmulsion (VI) : Radioactivity ofsome Japanese LiparitesHayase, IchikazuHayase, Ichikazu. The Radioactivity of Rocks and Minerals Studied with Nuclear Emulsion(VI) : Radioactivity of some Japanese Liparites. Memoirs of the College of Science,University of Kyoto. Series B 1958, 25(2): 81-871958-12-05http://hdl.handle.net/2433/258527MEMOIRS OF      Vol.THEXXV,COLLEGENe. 2OF SCIENCE,Geology and UwtVER$ITY OF KYOTO, SERIES B,Mineralogy, Article 2, 1958The Radioactivity of Rocks and Minerals Studied             Nuclear Emulsion VI     Radioactivity of some Japanese 'LiparitesGeological             By      Iehikazu HAYAsEand Mineralogical Institute, University of Kyoto     (Received July 26, 1958)with                                 Abstraet    Radioactivity of seme of Japanese liparites is measured by means of nuclear emulsiontechnique. As the result, the radioactive elements in liparite, as in gyanite, seem to be oflater Åërystallization. Characteristic distribution of radieactive elements in acid volcanic rockshas been studied Qn some of Japanese liparite samples, and the results are reported.                               Introdudtion    It is said that the radioactivity of igneous rock increases with the acidity of therock, andtherefore Iiparite must be of the highest order in radioactivity among allthe volcanic rocks. Distribution of radioactive elernents in igneous rocks shows nogreat difference between the plutonic and the volcanic series. In this paper thepresent author aims at mere prelirninary results concerning the radioactivities ofacid volcanic rocks. Up to the present time the radioactive investigation of vo}canicrocks has been rather neglected-due to the fact that granite has minute radioactlveminerals as various accessory species, while liparite lacks them. The behavier ofradioactive materials in acid volcanic rocks indicates distribution of higher concent-ration in the residual of Sne crystalline part of those rocks than in the porphyriticlarge crystals. That is to say, the radioacU'vity must get more condensed in theresidual liquid which ahy "Magma" leaves behind.     The present author intends to avoid the word "Magma", but here he under-     stands by it the rock-forming raw materials. He finds no reason to believe     that any material in liparite is derived directly from the primordial "Magma"     The discussion thereupon will be presented in sorne later papers.                 Radieaetivity of some Japanese }iparites    The measurement of radioactivity was carried out by contact autoradiographlc82 lchikazu HAyAsEmethod. Generally, the alpha track number per unit area on the uncovered thinsection of liparite during unit time was carefully counted under the microscope.The exposure time extended, for example, 311 days or 115 days, as the detectableradioaÅëtivity of principal rock-forming mineral is very feeble.    In these cases, a special care was taken to keep the latent image of alpha tracksin the nuclear emulsion unfading during the Iong exposure time. The blank tracksejected from the radioactive rnaterials in the plate glass or emulsion itself, thoughonly of minute amount, have been accumulated during such a }ong time. The photoplates used in this study were the autoradiographic photo plate (15 microns inthickness) manufactured by Fuji Photo Co. Ltd.      If it is tacitly assurned that radioactive equilibrium exists in these liparites,      and as the alpha permeability (Åë) of these rocks is 4.74 and the density of      them 2.7, the foi}owing values result from EvANs and GooDMAN's (1941)i)      and YAGoDA's (1949)2) data :           Granitic roÅëks a/mg/hour 2.2Å}0.2                           U ppm 3.0Å}0.3                           Th ppm 13Å}2.0           T.--di (25.73 U+7.80 Th)           T.la-O.OO0848 for liparite      The surface alpha radioactivity of liparite can be given from the above quoted      data as T.==O.OO0282ajO.OO03 for rocks containing 1 ppm U and the cor-      responding amount of Th. In other words, the powdered rock activity emitting      2 alpha per milligram per hour corresponds to T.= O.OOe4.    The radioactive values of Iiparites are shown in Table 1. Here rocks of similartype and same mass have the sarne order of radioactivity, for exampie, inNishinomiya lipcarite (a fresh rock samp}e) its radioactivity varies from T.==O.OO05to O.OO07, and in Tsuyama rocks of the fiow breccia of liparite from O.OO03 toO.OOe4. But the glassy part of liparite tuff of Sanda amounts to O.OO19, and moreelaborate results wili soon follow. Rock like Wada Pass obsidian (Nagano Prefec-ture) is high in radioactivity; and this seems to be due to its intrusion into theTertiary granite corre}atable to the Kinbusan granite (Yamanashi Prefecture).    By the way, the radioactive anomaly of acid volcanic rocks is seen only in thetuffaceous or glassy rocks, but not in the fresh common liparite.    The alpha track counting on the photo plate was performed by scanning it onthe microscopic stage, traversing about iOmm long at 0.11mm wide. The radio-activity generally seems to be more hornogeneous in liparite than in granite, theabsence of minute radioactive minerals such as thorite and monazite abundant incertain granitic rocks seems to give this difference.                 Radioactivity ef iiparitic feldsparThe radioactivity of feldspar as a principal constituent is very feeble and canThe Radioactivity of  RocksTable and Minerals Studied with1. Radioactivity ef Liparite.Nuclear Emulsion VI 83    Rock Mass Locality i Recks I" N'igil ilff.'."IY' i,-'i-A'ffill5""nv tttttt'ttt " ne"'pt' 'tt'ttt'tt't Li",51eg,,E'-' "" """"'''''/1111,,1     " :Arima i "(porphyritic)l     ,, i046 i" i     . Io42i i" I                  ' 1l     . 1039 j" i                                               /t  " Shioze, Amako Bridge 11 " j     " isanda iLiparite tuff I western part of chigusa vil., s. Takanosu, l Liparite I Hyogo Pref.& Hyogo Pref• I i TSUX,aMa is. w. Tsuyama i Fiow breccia of I                                                 liparite I                                                                  i                                               L 11     " iKanzaki County, Kyogo Pref. I Liparite . I     " i, fihyioggUoSaprVeifl:, E• TOkayane, l Liparite l     •• Iikuno lkigggi5etuff l                  'f     rr Tsutazawa vil., Shirakuchi Pas$, Perlite ii                   Hyogo Pref. i i Kinosaki Hyogo 3<inosaki Kiradake-dani l Glassy perlite L                                               I t/     . Kinosaki lfi,h:l?,e.dO"iC i                                                                  I     ,, Izushi Pitchstone i     " Tango iMn• Liparite l IUI8f,O..a.".d, N'jO INiJo'San i Mica andesite l     ll iNafaharavii.udaco..t,, :.Gfi;2e3,gf8g'`e l                   Nara Pref. i     ,, IShimotaro-Mitohoshi, Dacite l                  iuda county l     " Tsttgeno vil., Uda County E Rhye-dacite I                  l II Miscellaneous Shionomisaki, Wakayama Pref. j Micro granophyre I     ,, INirasaki-Shichiriiwa, Liparite i                  Isoboishi vil., Yamanashi Pref• I l     . IKaga }Iakusan i lSiPph.Rl ,".litiC i                                                                  '.. me_ z...._....ve....1..w.._3g.ft.pass, Nagano prmm,f. I mmg..bg!dl.a.n. .l                             ( ) * number of samplesRadioactivity    (T.)O.OO05O.OO05, 0.0006O.OO06O.OO06O.OO06e.ooo7O.OO07O.OO19O.OO03O.OO02e.ooo3 (2) *o.eoo4 (3) *O.OO05O.OO06O.OOIOO.OO05O.OOIOO.OO03, 0.0002O.OO04, 0.0002O.OO05O.OO09O.OOOIO.OO03O.OOOIO.OO03O.OO03 (3) *O.OO04e.ooo3O.OO03o.ooos, o.oeo70:992?•. .9 i0918 ..84 Ichikuzu ffAYASE,only be detected by long tirne autoradiographic exposure. The size of most feldsparunder the microscope is quite unfavorable for the counting of Åíhe track number, themicroscopic observation demands much carefull and tedious calibration.    The adjustment, however, needs double processes: First, under the low powerobjective lens, we must see if there are not radioactive anomalies and inclusions.Secondly, if the radioactivity of feldspar is found to be homogeneous, then we mustturn to the high power lens. The feld here in this case exteRds about 1.8Å~O.01mm2.The average value of t'he feldspar radioactivity must, at least for several fields, bemeasured by sliding the thin section. The adjustment of the emulsion with the rockthin section is helped by the three cross marks recorded on both of them. First theplate glass is pasted together directly with the siide glass, separating the emulsionfrom the reckthin section with a distance of some 2mm (the thickness of two glassplates). Naked eye adjustment will soon attain to so close a coincidence, that evenmicroscopic examination finds only small deviation of less than some 30 microns.    In emulsions expesed even 311 days, the alpha track nttmber in one microscopicfield counts only from 0 to 2 for quartz and from 3 to 10 for piagioclase feldspar.Besides, the blank tracks must be taken into consideration, especia}Iy when theemulsions are not fresh and multiple star tracks are found.    The fresh liparitic feldspar has the radioactive order of T. =O.OO02 in case ofsodic plagioclase and orthoclase. In sericitized feldspar the radioactivity is stil!higher. The altered feldspar. replaced with the dusty earthy material which iscomposed of micaceous browR or yellowish material has much higher radioactivity.    The prophyritic quartz of liparite shows feeble radioaÅëtivity. (T.==O.OOOIor less) -..                        Table 2. Radioactivity of feldspar.Locality Is Rocks                     FeldsparArima  }rNishinomiya le46TsuyamaNishinomiya 1037  ,, 1042t" le37EilllLiparitePorphyritic lipariteLipariteTuff breccia oflipariteLipariteLipariteLipariteEEEIIiZonal plagioclaseFresh plagioclaseYellow altered plagioclaseOvoidal sericitic plagioclaseAltered dusty yellow plagioclasePlagioÅëlase with pale ye}low corePlagioclase with dusty browncoreFresh ortheclaseRadioactivity   ( T.)O.OO02O.OO02O.OO03O.OO06O.OO13O.OO05O.OOI2,e.eoo2O.O020                RadioaÅëtivity oÅí colored raiRerals of liparite    The colored minerals of liparke show high radioactivity, but do not containminute radioactive minerals as gran2tic biotite does. Table 3 shows the radioactivityof colored minerals such as biotite, hornblende and chlorite, some of which areThe Radioactivity of Rocks and Minerals Studied with Nttclear Emulsion VI 85higher in radioactivity than that of altered plagioclase of liparite. Even in all theseprincipa} rock-forming minerals, the radioactivity appears to be heterogeneouslydistributed.    The spherulitic liparite of Kakusan contains epidote-like radioactive mineralswhich are of radloactive heterogeneity too, and the brownish part with highbirefringence has higher radioactivity than the transparent pale bluish part with lowbirefringence. This may be due to the heterogeneity of chemica} composition, forinstance, to the different amount of rare earth and so on.                    Table 3. Radieactivity ef co!ored minerals.LecalityNishinomiyaArima  tl  tsKase vil.,Hyogo ?ref.TsuyamaHakusan  rl1037RocksLipariteLiparite  }tPorphyritic lipariteLipariteTuff brecÅëia oflipariteSpherulitic liparite  ItColored MineralIKaolinized bietiteChloritized biotiteChlorite and epidoteBiotite clotBiotiteGreen hornblendeBrown epidotePale bluish epidoteRadioactivity   (T.)O.O026, 0.0036O.OO03e.ooo7O.O027o.ooll, o.oeo4o.ooes, o.ooo2O.0134--O.O067O.OO18                   Radioaetivity of liparitic ground mass    The radioactive materials in igneous rocks are contained in the main rock-formingmineral and glassy matrix. Even in granitic rocks, the comrnon accessory minerais,                   Table 4. Radieactivity of }iparitie groundmass.LocalityNishinorniyaArirr}aSandaArimaIkunoWada PassAkahoTsuyamaTsuyamailakusan1037RocksLipariteLipariteTuffPorphyriticlipariteLipariteObsidianTuff brecciaTuff breccia    rfSpherulitic liparitePart of the  rocksGroundmassGroundmassGlassygroundmassGroundmassGroundmassGlassGroundmassGlassClouded MatrixMatrixRadioactivity   ( T.)O.OO07e.ooosO.O025,0.0008e.oo17O.O022o.eoos,O.OO09,O.OO05,0.0009O.OO16o.oellO.OO15o.eoo6Total activityO.OO06O.OOG5O.OO19O.OO06O.OOIOO.OO04O.OO04O.OO03O.OO0786 Ichikazu HAyAsElike zlrcon, sphene and so on, occupy less than 20 percent of the total radioactivityin the rocks, and liparke has no such minerals. Feldspar, colored minerals andglassy matrix of liparite are the major source of radioactive elements, and especiailythe last oRe is petybgenetically most interesting. (See Table 4)            Radioactivity of tuinute aecessory minerals in Iiparke    Here, we must alude to the mildly radioactive comrnon accessories: zircon inliparite. They are all transparent and feeble in radioactivity. (See Table 5) Involcanic rocks, especially in' liparite, these accessories are contained in matrix orglassy part. The highly radioactive rninerals comrnon in granite, such as uraRo-thoyite or uraRinlte, cannot be seen in liparke so far. The absence of zircon iRbiotite and feldspar, but its presence only in matr2x or glassy part, seems to tell uslater origin of liparitic zircon.                 Table 5. Radioactivity of minute accessory minera}s...._.L_L9.9eilt7.._...ww.ww....... Minerai t.tt POSit'O.n.g,k.t.hethin..i ..gegi<o.)l}f.girity .  Nishinomiya l037 Zircon Matrix e.2046                          ,, ,, 0.4255                          . ,, O.e617                                                          i                          ,, ,, , O.0482                          . . 0.1157               • . " 0.1215                          . ,, 0.2490g:gs489 , ll I ,.A;,, I g[ggg9  Nishinomiya l042 l " Matrix 0.594e                          " ,, O.0755                                      l  Shionomisaki Brown zircon I ,, O.0165                                  Summary    1. Radioactive behavior of liparite differs from that of granite.    2. In liparite, transparent zircons of feeble radioactivlty are contained only inthe matri:.    3. Matrix or glassy part of liparite shows high radioactiyity.                              Aeknewledgement    The present author expresses his thanks to Prof. A. HARuMoTo, Assist. Prof.H. YosHizAwA of the Geological and Mineralogical Institute, University of Kyotofor their help and advice. Funds necessary for this investigation has been partly       The Radioactivity ef Rocks and Minerals Studied with Nttclear Emulsion VI 87defrayed by the Grant in Aid for Fundamental Scientific Research of the Ministryof Education.                               References1) EvANs, R. D. and GooDMAN, C.: Radioactivity of rocks. Bull. Geel. Soc. Amer. 52,      459-590 (1941).2) YAGoDA, H.: Radioactive measurements with nuclear emulsion. Tohn Wiley, (1949).

The Radioactivity of Rocks and Minerals Studied with Nuclear Emulsion (VI) : Radioactivity of some Japanese Liparites

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The Radioactivity of Rocks and Minerals Studied with Nuclear Emulsion (VI) : Radioactivity of some Japanese Liparites

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