島根大学地球資源環境学研究報告 24，53～58ページ（2005年12月） Geoscience Rept．Shimane Univ．，24，p．53～58（2005）

國Majoranαtraceelementabundancesin＜180and180－2000μmfractionsofstreamsediments fromtheHiiRiver，ShimanePref◎cture，

Edwin Ortiz＊and Barry Roser＊

Abstr3ct Stream sediments collected from4710calities in the of were hand sieved to separate the＜ 180μmand180－2000μmfractions．M司orandtracecompositionsofbothfractionsineachsampleweredeteminedbyX－ ray fluorescence analysis．Elemental abundances contrast significantly between the two size fractions．Average abundances of SiO2，K20，Ba，and Rb are greater in the l80－2000μm fractions，whereas the remaining elements are generally more abundant in the＜180μm fractions．Loss on ignition values are also greater in the＜180μm fractions． Average compositions of both fractions show similar nomlalized distributions to average upper continental cnlst．The greatest depart皿e from upPer continental cnlst composition is observed in the＜1801αm ffaction，with enrichment for several ferromagnesian elements（V，TiO2，Fe203t，Sc）and for Zr，Y，and ThJn both fractions，Nb，CaO，Na20，Sr，Rb， MgO andNi＆re slightlydepletedrelativetoUCC．

Key words：Stream sediments，Hii River，geochemistry，major and trace elements

and specific discussion will be published at a later date．The IntrO（IUCtiOn dataset presented here is part of a regional geochemical Although elemental abundances in the composition of database for the northem San’in region．This project began stream sediments reflect the geochemical characteristics of with the study of the Kando and the Hino Rivers（Ortiz and lithotypes present in their catchment，they are also Roser2003；Ortiz and Roser2004a，b）and greatly increases innuenced by a variety of processes that operate between （by over ten times）the density of geochemical data the source and the sediments produced．Such processes available for stream sediments in the area． include weathering，size sorting，heavy mineral placering effects，and the effects of addition of detritus from Lithology ofthe Hii River Basin geochemically disparate source rocks．The factors involved in these processes have been the subject of numerous In the regional context the distribution of lithological studies（e．g．Basu et al．1990；Johnson，1993；Ohta et al． units in the Hii River drainage basin is relatively simple． 2004；Avila et a1．2005）because they provide information Cretaceous to Paleogene felsic to intennediate granitoids crucial for the interpretation of phenomena of geological and volcanic rocks extend throughout most ofthe catchment and environmental interest． （Fig．1）．Granitoids occupy the m勾ority ofthe central basin， This article reports X－ray fluorescence（XRF）analyses of whereas less extensive volcanic rocks are concentrated ＜180μmand180－2000μmfractionsof47streamsediment towards the southem edge of the watershed．Lithotypes samples collected from the Hii River．The Hii drainage among the plutonic rocks include granodiorites，granites， system is located in eastem Shimane Prefecture，and drains granitepolphyries，granophyresandquartzdioritesto an area of about930km20ver a main channel length of gabbros，whereas the volcanic rocks are mainly dacite to approximately82km，stretching from the headwaters in rhyolite lavas and pyroclastics （Editorial Board of Mount Sentsu to the westem end of Lake Shir“i（Fig．1）． GeologicalMap ofShimanePrefecture‘‘EBGMSP”1997）． The Hii River supplies a m司or proportion of the sediments A second group of lithological units including Miocene entering the Lake Shinji－Lake Nakaumi coastal lagoon volcanic and sedimentary rocks，principally of the Hata， system．The historical，cult皿al，socia1，environmental and Kawai，Kuri，Omori，and Fujim Formations，crops out economic importance of this area has been reviewed by along the westem boundary and in the northeastem Tokuoka et al．（1998）． extremity ofthe drainagebasin（Fig．1）．The main lithotypes The pu耳）ose of this report is to present the data obtained arerhyolitetodaciticlavas，andesites，andpyroclasticrocks， by XRF analysis，along with a brief description of the along with locally derived sandstones，conglomerates and general variations of elemental abundances in two size shales（EBGMSP1997）． fractions of sediments from the Hii River．More extensive The characteristics and interrelationships among most of theunitscroPPingoutinthisdrainagebasinhavebeen

＊Dept．ofGeoscience，Shimane University，Matsue690－8504，Japan described in a number of studies（e．g．Iizumi et a1．，1984，

53 M司orandtraceelementabundances in＜180and180－2000μmfractions ofstream sediments 54 from the Hii River，Shimane Prefect皿e，Japan

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Fig．1．Map showing thegeneralizeddistribution oflithotypes in thecatchmentofthe HiiRiverand location ofsample sites．Geologybasedon the1：200，000geological map ofShimane Prefecture（Editorial Board ofGeological map ofShimane Prefecture，1997）．

Kagami et a1．，1992；Yamauchi and Yoshitani，1992；Kano 2004．Weather conditions were clear and dry，and stream et a1．，1994；Roser et al．，2001）． flows norma1．Sub－samples were collected with a plastic water scoop from active channels over a length of20－50m，

Sampling and SamplePreparation andthen storedinplasticzip－topbagsas single representative samples foreach site． ．F’ε14Sα即ling Selection of sampling sites was made with the aim of Sampling was carried out on five days during autumn achieving a unifom distribution that would cover a11 Edwin Ortiz and Barry Roser 55

1ithological units present in the draimge system．Locahties were selected from1：50，000topographic base maps on Hii River 一一怦鼈黷P80－2000μm fraCtiOn 10 Fraction average！UCC 一一Z一一く180μm fraction which geology ffom the．1：200，000geological map of Shimane Prefecture（EBGMSP1997）had been overlain．At 1 a few localities samples could not be collected due to difficulty of access or paucity of sand－grade sediment，and sites were displaced slightly f士om those originally intended． 0．1 Location of the sampling sites is given in Figure1．Overall sampling density was one sample per l9．7km2． 0．01 Nb Pb U K Ca Zr Th Na Sr Rb Mg La Ce Si Al Ba Sc Y Fe Ti Ni Cr V Fig．2．Multi－element plot showing the average composition Sα即16Pr8四嬬ion （anhydrous normalized）of＜180and180－2000μm fractions from Bulk samples were dried at80－90℃the day after the Hii River（data from Table3）normalized against the Upper collection，and subsequently hand－sieved to remove pebbles Continental Crust（UCC）average ofTaylor＆McLennan（1985）． Elements are arranged from left to right in order of increasing and clasts coarserthan2mm．Average weight ofthe＜2mm normalized abundance in average Mesozoic－Cenozoic greywacke fractions was993g．These＜2mm fractions were split （Condie1993）relative to UCC，following the methodology of （mostly into eighths or quarters），and an appropriately sized Dinelli et aL（1999）．The m勾or elements are normalized as split was then passed though an83mesh stainless steel oxides． sievetoseparatethe＜180and180－2000μmffactions．On average，the＜180μm fraction comprised12wt％of the＜2 had LOI values＞5wt％，whereas in the180－2000μm mm bulk materia1．Only in four samples did the＜180μm fractions values were considerably lower，with most fraction exceed20wt％．The＜180μm fraction formed a samples＜2wt％，and only two exceeding5wt％． particularly large proportion （70wt％）of the sample Summary statistics for the fractions from analyses collected at site31． normalized to100％LOI－ffee are given in Table3．Contrast Both fractions were then crushed separately in tungsten in average elemental abundances between the fractions is carbide mills，applying the procedures described in Ortiz significant．Abundances of most of the elements analyzed and Roser（2004b）．Sub－samples（10－12g）of the crushed aregreaterinthe＜180μmaverage，exceptfor SiO2，K20， fractions were then placed in glass vials and dried for at Ba，andRb，whichhavehighervaluesinthe180－2000μm least24hours at110℃prior to dete㎜ination of loss on fraction．Although there are several anomalies，the average ignition（LOI）． composition over the entire suite is similar to that of average upPer continental crust（UCC），as shown in Figure 2．The180－2000μmfractionaverageisslightlydepletedin AmlyticalMethods most elements relative to UCC，and only shows slight LOI was estimated for each sample from the net weight enrichment in Pb，Ce and V．The pattem is relatively Hat loss after ignition in a muffle fumace at1000℃for at least overa11，and greatest depletion is seen in Nb，Ni，Cr，CaO twohours．Ignitedmaterials were retumed to glass vials and and MgO．In contrast，the＜180μm fraction average is a held at110℃for at least24ho皿s before the preparation of little less regular，exhibiting both enrichment and depletion fusion beads for XRF analysis（anhydrous basis）． relative to UCC．The largest depa血re of the＜180μm Major elements and14trace elements（Ba，Ce，Cr，Ga， fraction average from UCC composition is seen in the Nb，Ni，Pb，Rb，Sc，Sr，Th，V，Y，Zr）were determined from enrichment ofV and the segments Zr－Th and Sc－Ti．Nb and glass beads，prepared with a伽x（80％1ithium tetraborate several mobile elements（CaO，Na20，Sr，Rb，MgO）are and20％lithium metaborate）to sample ratio of2：L depletedrelative to UCC，as they are in the l80－2000μm Analyses were made using a Rigaku RIX－2000XRF fraction average．In genera1，however，the pattems of the spectrometer at Shimane University，and following the fraction averages are very similar to those shown by methods，instrument conditions，and calibrations described equivalent size fヒactions ffom the neighbo皿ing Kando and by Kimura and Yamada（1996）．More detailed descriptions Hino rivers（Ortiz and Roser2003，2004a，b）． of the methods used are given by Roser et al．（2000，2001） and Ortiz and Roser（2003，2004a，b）． Conclusions

Average chemical compositions of＜180and180－2000 Results μmfractionsofstreamsedimentsffomtheHiiRivershow M勾orandtraceelementanalyses ofthe＜180μmand180 significant contrasts in abundances． LOI and average －2000μmfractionsarelistedinTablesland2，respectively． abundances of most elements are generally greater in the Data are listed on a hydrous basis，with total iron expressed ＜180μm fねctions，but the180－2000μm fractions have as Fe203t．LOI values in both fractions were low，in all cases higher average contents of SiO2，K20，Ba and Rb．Average less than lO wt％．In the＜180，αm fractions only l4samples compositions of both ffactions are similar to that of the M勾orandtraceelementabundances in＜180and180－2000μmfractions ofstreamsediments 56 from the Hii River，Shimane Prefecture，Japan

Table1．M司orandtrace elementanalyses ofthe＜180μm fractions，Hii River（hydrousbasis）． M司orelements wt％，traceelementspPm． SaNr SiO2 TiO2 AI203Fe203t MnO MgO CaO Na20 K20 P205 LOl SUM Ba Ce Cr Ga Nb Ni Pb Rb Sc Sr Th V Y Zr％〈180μm蝿塊8。翅㈱識梱搦灘㎜贈撰講鰹欝9。佃悩握撰秘㎜95羽旧禦駕瑠羅 給221713171624293228171820201617171618σ1822211929212722132620勿1518四171511411320172218伯21“属262275350743餌82928194鱈5759506242⑳539257677733502856伯糾6096063829864365043112餌386740銘m岱㈹121409“α価10加σ0610銘α加湘並糾並⑩旧⑩葡⑯葡α⑲⑳祀湘瀞理皿α」0調儒調認想旧⑬⑯霧瀧欝携繋畿彊譜瀧携鰯詔罵護㈹灘獅謝欝説謬魏籔螺 1 1餌422315203956685562伯2738204331363227325360餌45392530嘱20274132嘱04525210属24153031762474引 1 1張蟹竈糊鱈鷲欝謡鰯叢幾欝揚穐鵬纂醤留鴇¶℃纏愕欄堺糾7957303619糾59252221伯18烈20櫓272538357942323024桝釧262438273526糾糾2428娼2847212425232218 イー －講謂護樂腰偽顔瀧講枷価脇錨類懇蹴蜷講護霧謡謡欄鷲瑠泌 判塗毛4おマ身⑩荊覗⑬嘱巧⑯覗娼⑲⑳引囎偽必必妬卯伽舶舶朝理㏄姻茄船研銘㏄菊期魂菊嗣菊菊η菊66 37 50 111111』ー1 四晃蓄葡髪粛98留68臆肝9。£β鴇創茄・8器豊3。2398器酒39引69る9餌・。68袷£βコ2乃班 1 1211 1 1 68 ααααα00．α 0000αααα00 0000000000 0000000000 0000000095 72 73 0000αααα 00α00αα000 0000000000 0000000000 0000000090 ㏄器釦留瓢る6雪紀歪銘鷺鴛⑯蛋留加蟹驚茄£3餌碧β。舞釜釧⑩群駕 11 121 73 11 7978102826161913101112918898912”19劉侶17102018813伯211829261375128属131910212323 92 億阻50億216皿59仔“658105＆9笹器楓風22勿風94136518幡梓1221風9732822469599風⑳趾9㈹松425五松¶11斜610藪杁12519614676Z569“0斜8621414σ6ね693勿9125886296457344β72293鴻252βOβ4503β」4つ95393君70β357 HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHαtααααttttααt1αtt1001111110000α000α1000000101154αa8632327α4364245a343456α590α455α38a54ヰ4346933＆4461144772999099623607867786661795753661870h6565而帥56333888昭η櫨田節3862㎝。9万6526餌53。328。2。8福鵠馴56田伯駆引o。ハ田38刀娼9。53花餌01001111111111可111111111111111111221101011111123222322222222321233222212221222233211112222113344423322212212123333231121023233312312111110222221222111121212222222212202222221232411111121223810225622422210021248569622223343635645699999999999999999999999999999999999999999999999899999888899889989999989999899989998999989889911112211211114111111111112212211111121111111128798007907887596667867578007007665861975778794�渠f18伯3925642424伯2530烈262426恰2312152122231525171930191820穏163127得703879格3917273692駐7120a9687727ヰ53乳95ス55乳1532αα5α8401844ス78285363371715渇6545311902051437832195238つ796お84溜」」∋13つ733754」つ2お名03937635つ1453β14627403君5お076070£ T7 R5 O6 T8 W6 Q9 S9 U3 Q5 U8 2111111111111111111112112111111211111212 U0 S8 V6 X6 R9 V2 O8 T1 Q1 X1 U5 R8 T9 X8 O0 W6 P0 V9 P3 X4 Q9 S1 U3 S1 X4 ｸ917261815769116911101412251714139斜1010712⑩108119882011187710688W8 U0 V9 T7 ･29朽36360796310799377988665742168300886566593638嘱721127476667433849侶1722232874 T7 P2 �P2娼329591引532485⑫770493900220糾08㎝嘱7291図86餌906689691173697349758258930447W9 V9 W6 T2 T7 U1 P2 �P54167455956怖5037023385944594526323588756616726999922価4923830063伯2143453622T8 W8 O3 V2 T2 U9 Q4 W3 O9 T8 鰍U43735466340馴7264907473022585桝577258428472057213855952026297糾4565375250 T7 W6 11』ー1111111 T9 P9 V6 T7 V3 W9 O3 T1 Q1 T3 R7 S7 U0 鰍T0683362糾6377809577糾668235糾7430829659餌6766589841引646261馴476349 U0 O2 Q0 Q2 T8 W5 W0 V6 a59626462606260565659635758引575662糾625758636261636864餌60626153R2 S7 O1 T9 冾P48227424993461435糾29460580359623糾434893904265旭9086824982糾U2 R8 W6 Q5 W5 ｢307636823996得66餌17869672姐18946903勿6797得33璃43150830S9 1111111111 V7 X0 1111 1 1 1 1W8 111 1 1 1 R8 T2 U7 V6 R7 V6 U4 1111111111 Q7 X6 V1 X5 V5 S9 W6 U8 P7 U4 1111111司ー 冾X9930708776927

Notes：SaNr＝Sample number．LOl＝loss on ignition．％＜180りm：wt％ofく180μm fraction in each sample．Total iron as Fe203．

Table2．Majorandtrace elementanalyses ofthe180．2000μmfractions，Hii River（hydrousbasis）．Majorelements wt％，traceelements ppm． SaNr 鴫一 TiO2 AI203 Fe203t MnO MOOOOOO1000011101000000000000010000000100011111090 CaO Na20 K20 P205 しOI SUM Ba Ce Cr Ga Nb Ni Pb Rb Sc Sr Th欝鑑瑠犠欄幾翻饗叢蟷㈱㈱窩揚”の萄℃欝纏蟷㈱辮鷲梛伽95欄価縄覆V Y Zr ％Csf 凋乏β46お4身⑩荊覗照嘱菊⑯羽娼⑲舶必卯船必必⑳”⑳舶舶朝聖㏄桝茄部研㏄㏄菊痢魂菊嘱菊菊4菊ﾗ棚㎜鼎羅欝躍羅闘礫舳㎜器㎜駕認器器懸醤雑磯將舗齢黙 1 a忍6湘あ6餌餌刀餌』9£6忍8隅釦加濁桝加澱£6加釧加研餌湘刀£8謂加翻葡魂澗£9劔加釦認綿π粛⑩⑳儒コ9盈麗幡92糾17330396792878926567701814805326929581490680246939029846356537088870050555伯388562888585 1 謬叢繋岬纏篇黎竈溜魂輔㈱講覇贈翻鰹鷲篇蝿翻繋輔矧鑛篇 ーイー 1 1 伯1516裕13槍28281848262519加2418餌1719伯151412181415191217191414131514“2523135525691729141623－』ー1111 1111 11 11 HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH000000000 27 111111111111111111111111114111111114111111111123444046211165315333333031340280013332421144343329 1452114534945769444422333341371163221523155675895｢籍68π彊昭8596田35網68伯35侶穆刀89訴53田。589器霧α952893。9お56網爵66落630000000000000000000000000000000000000000000000000100011121111111101000001100100000001020111111780797228563533500806677752593577665705056537161211112111222212111211111110120011111100011111143 3333232221222211212332122211101122222220111112009 3333342322221221222333333323213323333243422212161 000000000 04 101101200003311312100001023027000110211213323289999999999999999999909999990999999999999999999988888989888988889999189899909989989888888888879。6 29 213431212 1 05952雫381897039483265288164102一2030836233164750111111111211111111111111111 11 111111111111111255752694605775384455541424894890134335342675653605805799275568645696874667385444554552786555552212205442644745344454334510461259862813166759114 5α3511＆564643974816645224641810035425238314451143550£303422β97740β」5コ」73ββ」739ββ32β03262β6忍63β511604蕉19145354545373865784272345433562595354556203お27」350395β5699590」潟20」43β3」0797つ224β5忌7」54桝63袷35奮団場欝摺姿瑠η9698訓釧6956藷367引囎朽囎盤25悩33嘱寵価稠郷122111123111111111111111112 22 1 1111111111155249050641562371726171134872278199714954775831 11 1 113211111111 98 85 52244814653766438817685840465174960157122304753 衷ｩ325025565792020159餌8987775056505732363642434142⑫51581717383635302755334023576269716674e3307引娼253339嘱80餌67餌檜俗3808鴻68920553鍵引659817怖㎝価02娼葡糾葡8920伯6628053728雀98葡O4 R0 |6656糾2331049562銘058122597060糾餌侶29糾46給39322068890879637310092730402508142311186917“O5 W6 U0 P9 1111 12 1 111112｢3785596435732530202332030340083099⑩7100999304167468902076789575957684221798862943253120惚V9 T8 T9 O3 冾Q8釧。895墨5。6。詔弓83。6器得3699別69薯36据韻26幕乃男％η壽乃鋸35餌T3 Q1 V5 T6 Q7 O3 R2 ﾘ083269888081餌59466373鱗727377040729068700恰糾0802糾15096479787801707195637665665162糾X0 1 12 1 1 P6 ｵ22嘱927292173609図8275357896070784988438019974498877引4759団947306219969140465610984O6 冾Q2355246引332831322733262929382532293033373916引3219ね522528192237嗣2736373330263927X1 T6 O4 W9 X9 O6 W7 X5 Q8 O4 ー 4ー U2 O7 X7

イー 1 1100000000 V7 0000000000 O4 イー X4 }娼堰52596577018803856816784522畠87⑫11909566828095糾859094626442779394糾O3 鰍W78888889389908287948093859393939794308899889194978585829389939196789087 O6 O7 O5 O4 O8 O5 O6 O5 0000000000 0000000000 O5 1 1 111 11 O5 O6 O3 O5 t050802060702020706060705090405020811101008121 1 411

11 1

0000000000 0000000000 1 1 1

11 11 － 1 00000000 00000000 1 11235 111111

2

Notes：SaNr＝Sample number、LOl＝loss on ignition．％Csf：wt％of180－2000μm fraction in each sample．Dash（一）：not detected．Total iron as Fe203． Edwin Ortiz and Banry Roser 57

Table3．Summ肛ystatisticsforall＜180and180－2000μmfractions（anhydrousno㎜alizeddata）．

《780μm斤ac60η ‘78082000μm斤acσoη η＝46† η＝47

Element Mean Min Max SD Mean Min Max SD M司’orelemeηfs碑％ナ Sio2 63．64 54．14 71．57 3．52 72．49 58．88 81．96 4．52 Tio2 1．05 0．51 2．02 0．35 0．52 0．12 1．04 0．22 AI203 16．25 12．78 21．55 1．99 13．85 10．13 25．84 2．63 Fe203t g．68 3．55 21．92 3．70 5．14 1．05 14．76 3．12 MnO O．21 0．11 0．44 0．06 0．11 0．05 0．26 0．05 MgO 1．52 0．66 2．29 0．37 0．88 0．40 1．66 0．29 CaO 2．55 1．09 3．79 0．60 1．69 0．63 3．11 0．51 Na20 2．63 0．40 4．59 0．98 2．30 0．93 3．69 0．68 K20 2．35 0．89 4．39 0．61 2．95 1．18 4．34 0．75 P205 0．12 0．06 0．23 0．04 0．06 0．02 0．13 0．02

ηace e，emeηfsφρm少 Ba 408．2 311．8 540．4 53．1 467．9 337．3 613．2 63．2 Ce 83．O 37．2 214．8 37．7 36．7 16．4 149．1 19．5 Cr 43．8 10．9 138．0 25．9 13．3 0．0 55．4 13．3 Ga 18．8 15．1 26．9 2．2 15．2 9．3 24．9 2．9 Nb 12．5 6．6 26．8 5．1 7．0 3．0 19．0 3．0 Ni 14．8 5．1 30．6 6．5 5．0 0．3 23．1 4．0 Pb 26．9 12．0 84．5 14．9 21．5 11．1 72．2 11．3 Rb 73．6 33．2 172．3 25．6 90．0 36．8 175．0 30．2 Sc 16．3 5．0 28．7 4．7 7．9 0．6 23．5 5．5 Sr 251．6 133．9 482．8 72．9 221．5 97．3 501．3 77．2 Th 16．8 4．9 61．2 13．3 6．8 2．4 29．9 4．2 V 228．1 50．6 573．1 121．2 103．2 6．5 355．2 83．9 Y 33．3 18．6 81．0 13．9 15．4 6．8 36．3 5．7 Zr 449．0 171．4 1250．0 271．7 123．2 65．3 331．1 45．8

Min Minimum Max Maximum SDp Population standard deviation

Notes：†oneく180μm samp口e could not be analyzed．Total iron as Fe203．

upper continental crust，although the＜180μm fraction Ch8nπcαl G80109』y，104，1－37． Dinelli，E．，Lucchini，F．，Mordenti，A．and Paganelli，L．，1999， shows slight enrichment in some ferromagnesian elements Geochemistry of Oligocene－Miocene sandstones of the northem （Sc，Fe203t，TiO2，V）and in Zr，Th，and Y．In both fractions， Apennines（Italy）and evolution of chemical features in relation to Nb，CaO，Na20，Sr，Rb，MgO and Ni are somewhat provenance changes．S84∫配8n‘oだソG80109』y，127，193－207． depleted relative to UCC． Editorial Board of Geological Map of Shimane Prefecture（EBGMSP）， 1997，Geological map ofShimane Prefecture（1：200，000）． Iizumi，S．，Mishima，H．，Okamoto，Y．and Honma，H．，1984，A strontium Acknowle“gements isotope study on the Neu granitic pluton and its mafic inclusion，San’in zone，Southwest Japan．／0μrnα1げ∫h8 ノゆαn8s6 Asso6∫α∫’on φ 0皿thanks to Akihiro Takahashi，Edier Aristizabal and ル1in8rα’09’∬s，P8か’olo9∫s‘sαn4Econo〃1’6G80109∫∬s，79，89400． Johnsson，M．J．，1993，The system controlling the composition of clastic Balmer Echeverry for their assistance d皿ing fieldwork，and sediments．G8010g∫6α1Soc妓yげA配副。α5p8c∫αl Pαp8r，284，1－19． to Yoshihiro Sawada for access to the XRF． Kagami，H．，Iizumi，S．，Tainosho，Y。and Owada，M，1992，Spatial variation of Sr and Nd isotope ratios of Cretaceous－Paleogene granitoid rocks，Southwest Jap＆n Arc．Con加加∫’ons孟。〃『’nα010g』yαn4P8かolog』y， References 112，165－77． Kano，K．，Yamauchi，S．，Takayasu，K，Matsuura，H．and Bumo，M．，1994， Avila，P．F．，Santos，」．M．，Ferreira，E．and Cardoso，E．，2005，Geochemical Geology of the Matsue district，with Geological Sheet Map at scale1： sigmtures and mechanisms oftrace elements dispersion in the area of the 50，000．Tsukuba，Geological Survey of Japan，126p．＊ Vale Das Gatas mine（Northem Portugal）．10配rnα1‘ゾG80ch81n∫6α1 Kimura，J．1．and Yamada，Y．，1996，Evaluation of m司or and trace element Eηワ10roπon，85，17－29。 amlyses using a且ux to sample ratio oftwo to one glass beads。10μrnα1げ Basu，A．R．，Sharma，M．and DeCelles，P．G．，1990，Nd，Sr－isotopic 〃’n8rα10gy，P8∫ro！08yαn4Econo癬cG8010gy，91，62－72． provemnce and trace element geochemistry of Amazonian foreland basin Ohta，A．，Imai，N．，Terashima，S．，Tachibana，Y．，Ikehara，K．and Nak司ima， fluvial sands，Bolivia and Pem：implications for ensialic Andean orogeny． T．，2004，Geochemical mapping in Hokuriku，Japan：influence of su㎡ace Eαπhαn4P1αn8fαぢソS6∫8nc8L8π8rs，100，1－17． geology，mineral occurrences and mass movement from terrestrial to Condie，K．C．，1993，Chemical composition and evolution of the upper marine environments．A卯li84G80chε加s砂，19，1453－1469． continental cnlst：Contrasting results from surface samples and shales。 Ortiz，E．and Roser，B．P．，2003，Major and trace element abundances in the Majorandtraceelementabundances in＜180and180－2000μmfractionsofstream sediments 58 from the Hii River，Shimane Prefecture，Japan

＜180μm fractions ofstream sediments from the Kando River，Shimane compositions ofMiocene sedimentary and volcanic rocks from the Izumo Prefecture，Japan．G召oso’6nc8R81ρoπs qプSh〃nαn8Un’v8rs妙，22，111－ －Matsue districts and Shimane Peninsula，SW Japan．G80s618nc8Rεpor‘s 120． ‘ゾSh〃nαn8Un∫v8rs妙，20，69－82． Ortiz，E．andRoser，B．P．，2004a，M勾or and trace element abundances in the Taylor，S．R．and McLennan，SM．，1985，Thεcon加8惚l crμsむi∫s sand fractions of stream sediments from the Kando River，Shimane oo規pos∫加nαn48volμ∫ion．Blackwell，Oxford，312p． Prefecture，Jap＆n．G80sc’8no6Rθpor∫sげSh珈αnεUn’v召rs’乏y，23，17－25． Tokuoka，T．，Takayasu，K，Kunii，H．，Takehiro，E and Sampei，Y．，1998， Ortiz，E．and Roser，B．P．2004b．M司or and trace element abundances in the Improving lagoonal environments for future generations－a case study of ＜180μm and sand fractions of stream sediments from the Hino River， lakes Nakaumi and Shinji，Japan一．Lαg況nα，5，1－1α Tottori，Japan．Gθosd8noεR8poπs犀Sh伽αn6Un∫v8rs’乏y，23，27－37． Yamauchi，S．and Yoshitani A．，1992，Miocene tectonics of the southem Roser，BP．，Kimura，」．一1．and Hisatomi，K．，2000，Whole－rock elemental Japan Sea and its adjacent area，〃召〃30かsρプ‘h6 G80109∫αzl Soc∫8町y6ゾ abundances in sandstones and mudrocks from the Tanabe Gmup，Kii 抑αn．37，31B26．＊ Peninsula，Japan．G80sd8nc8R81ρor∫sげSh〃nαn8Un∫vεrs1乏y，19，101－ ＊ l12． In Japanese with English abstract or summary． Roser，B．P．，Tateishi，Y．andNakayama，K．，2001，Whole－rockgeochemical

（要 旨）

Edwin O性iz・Barry Roser，島根県斐伊川から採取した河川堆積物の粒径180μm以下と180－2000μm フラクションにおける主・微量元素組成．地球資源環境学研究報告、24，53－58 島根県の斐伊川の47ヶ所から採取した河川堆積物を篩いがけして粒径180μm以下と180－2000 μmフラクションに分離し，主・微量元素組成の蛍光X線分析を行った。元素組成はこれら2つ のフラクションによって明瞭な違いを示した。SiO2，K20，B＆，Rbの平均含有量は粒径180－2000μm フラクションの方が180μm以下より多いが，これ以外の元素では一般に低い。灼熱減量でも粒径 180μm以下の方がより大きい。両フラクションにおける平均組成は最上部大陸地殻の平均組成に 類似している。最上部大陸地殻組成との大きな組成的違いは粒径180μm以下のフラクションで認 められ，それらはある種の苦鉄質元素（V，TiO，，Fe、0，，Sc）とZr，Y，Thに富んでいる。両フラク ションにおいて，Nb，CaO，Na20，Sr，Rb，MgO，Niは最上部大陸地殻（UCC）の平均組成に比べ てわずかに少なくなっている。