1. 赤川史典・吉田英一・ 與語節生・山 本鋼志(2004) 花崗岩割れ目周辺の酸化還元反応と二次的物質移動現象 ー地質環境中汚染物質の移動と長期的固定に関するアナログ研究-.  地質学雑誌, 110, 671-685.
  2. 山田味佳・山本鋼志・牛原康博・川井浩史 (2003) 有機態金属分析による大阪湾岩域の環境評価.環境化学13, 983-992.
  3. 吉田英一・山本鋼志・ 田中姿郎・與 語節生・Milodowski,A.E. (2003) 酸化還元フロントの形成と二次的物質移動現象. 地質学雑誌, 109, 548-558.
  4. 高柳幸央,山本鋼志,與語節生,足立守 (2000) 高知県福良地域の四万十帯白亜紀層状チャートの堆積環境 -ノルマルパラフィン組成・主要元素組成・希土類元素組成からの推定-,地質学雑誌106,632-645.
  5. 山本鋼志・田中 剛・川邊岩夫ほか (1998) 愛知県豊田市北東部の領家花崗岩地域の地球化学図. 地質学雑誌, 104, 688-704.
  6. 山本鋼志・森下泰成  (1997) 蛍光X線分析用微量元素標準試料の調整. 地質学雑誌, 103, 1037-1045.
  7. 山本鋼志  (1984) 静岡県西部瀬戸川帯の酸性凝灰岩および珪質泥岩の地球化学的研究. 地質学雑誌, 90, 479-496.
  8. 山本鋼志  (1983) 岐阜県上麻生付近の三畳系層状チャートの地球化学的研究. 地質学雑誌, 89, 143-162.



赤川史典・吉田英一・與語節生・山本鋼志(2004) 花崗岩割れ目周辺の酸化還元反応と二次的物質移動現象 ー地質環境中汚染物質の移動と長期的固定に関するアナログ研究-.  地質学雑誌, 110, 671-685.

   The focus of this study is a redox front formed along a fracture within the last ca. 105 y that is estimated by the geological setting and the features of the redox front's spatial pattern in Tertiary tuffaceous sedi-mentary rock distributed in central Japan.
   In this investigation, the redox band has been analyzed by XRF, EPMA and SEM-EDS for major and trace elements to understand the elemental profile, and the spatial distribution of elements from the fracture to the rock matrix.
   The XRF analysis showed that Mn is concentrated in three sharp layers, situated near the fracture surface. In contrast the most Fe-concentrated layer was seen in deeper part of the rock matrix. This suggests that fractionation between Mn and Fe has occurred during the front migration. The Mn-concentrated layers are accompanied by the enrichments of various trace elements such as Zn, Ni, Ba and Y. On the other hand, the Fe-concentrated layer is characterized by enrichments of P and also Y. EPMA analysis revealed that the Fe is distributed het-erogeneously in the rock matrices with high P enrichment Detailed SEM observation identified that fossilized microbe colonies occur in the pore space. Direct exanrination of the fossilized cell like structure with SEM-EDS showed that they are composed exclusively of Fe and Si. This observation and the results of incubation experiment suggest that the microbial activity played an important role in the concentration of Fe and other elements in the redox front under low temperature subsur-face condition. These lines of evidence can be used as chemical ana-logues of long-term contaminant fhation by the redox reaction that may occur in the geological environment surrounding almost any type of subsurface waste repository.

Key words: Redox front, Analogue, Elemental migration, Fixation, Microbial activity




山田味佳・山本鋼志・牛原康博・川井浩史 (2003) 有機態金属分析による大阪湾岩域の環境評価.環境化学13, 983-992.

   The bottom environment of Osaka Bay was assessed by comparing organometal composition of sediments from inner part of the bay (along shore from Kobe City to Osaka City) with those in coasts along Awaji Island. The organometals desiguated in this study are those extracted by toluene-methanol mixed solvent. The results howed that human effects seem to be stronger in the inner bay than in the area along Awaji Island; the former shows higher concentrations of Mg, Cr, As, Ni, Se, Sn, Hg, Pb, Co, Cu and Zn. The main results obtained in this study are;
1. The concentration of organomaguesium is apparently higher by 2-3 orders of maguitude in comparison with other organometals, suggesting the large contribution of chlorophyll contained in phyioplankton. The higher concentration of organomagnesium in sediments from the inner bay suggests that human-supplied nutrients may cause higher production of phyioplankton. The positive correlation of organomagnesium with organoarsenic and organolead suggests the possibility that arsenic and lead are also concentrated by phyioplankton.
2. Sediments from the mouth of Shin-Yodo River are enriched in organic forms of Co, Cu, Hg, Ni, Zn, Sn, Se, and Pb and those from the mouth of Muko River are enriched in organic forms of Co, Cu, Zn, Sn, As, Se, and Pb. Those metals may originate as pollutants from the river.
   However, all these organometals are not necessarily human-derived, because some may originate from other processes such as absorption of inorganic metals onto terrigenous high-molecular weight organic matter and from biological activity.

Key words: Environmental assessment, Organometals, Bay sediments, OsakaBay   


吉田英一・山本鋼志・田中姿郎・與語節生・Milodowski,A.E. (2003) 酸化還元フロントの形成と二次的物質移動現象. 地質学雑誌, 109, 548-558.

   In a geological disposal system for high-level radioactive waste (HLW), maintenance of a reducing geological environlnent is considered to be important for long-term safety. However, formation of a redox front in the near-field of a HLW repository can be accornpanied by oxidation of artificial barriers and basement rocks during the operational phase. In order to provide an analogue for secondary elemental migration associated with the formation of such a redox front, we examined granitic rock with a redox front formed along a fracture.
   Geochemical analyses revealed that Fe concentrations in the oxidized zone are higher than those of the parent rock, and that secondary Fe acculnulation occurred. Secondary accumulation of Mn was also identified in the oxidized zone, which has about 5 times the Fe concentration of the parent rock. These results show that these elements were firstly carried by reduced groundwater, and then oxidized and precipitated after oxygen diffusion into the matrix of the host rock.
   It is also found that heavy metals such as Pb, Ba and Rb are concentrated in the oxidized zone, and that the concentrations of Pb and Ba are also increased by about 2 times compared with those of the parent rock. The concentration of these heavy metals can be considered to occur due to adsorption on Mn precipitates, and this suggests that Mn precipitates are capable of retaining heavy metals within the oxidized zone. Additionally, it has also been revealed that REE and U have accumulated in parts of the redox front, and are considered to be adsorbed onto Fe precipitates.
   These results of an investigation into a redox front, show that secondary migration and accumulation of heavy metals was accompanied by redox front migration. Coupled phenounenon like these may be analogous to processes that Inight occur in the near-field of a HLW repository.

Key words: Redox reaction, Granitic rock, Fracture, Secondary elemental Migration, Iron oxide.   




高柳幸央,山本鋼志,與語節生,足立守 (2000) 高知県福良地域の四万十帯白亜紀層状チャートの堆積環境 -ノルマルパラフィン組成・主要元素組成・希土類元素組成からの推定-,地質学雑誌106,632-645.

   The depositional environment of Cretaceous bedded cherts and intercalated shales from the Fukura area, Kochi Prefecture, in the Shimanto Terrane is discussed on the basis of analyses of n-paraffins (C12-C38 ), major elernents and rare earth elements (REES). Radiolarian biostratigraphy confirlns that the bedded cherts had deposited durini Barremian.
   N-paraffins in most shale partings are low in concentration and are composed mainly of short-chained (C14-C18). The low abundance of long-chained n-paraffins with a strong odd-carbon number predouninance suggests that the bedded cherts deposited in an environment with little contribution of terrigenous organic matter.
   Some samples, in spite of their sampling horizon, shows lower Al2O3 /TiO2 ratios, suggesting that the bedded cherts deposited around a field of mafic volcanism with a large contribution of basaltic debris.
   Samples from the lower horizon have higher tot.Fe2O3 /TiO2 and MnO/TiO2 ratios than those of average shales and marine sedinrents. In addition, these are characterized by a negative Ce anomaly. This suggests a large contribution of Fe-Mn precipitates from hydrothermal emanations, originating from mafic volcanism. Salnples from the upper horizons have lower tot.Fe2O3 /TiO2 and MnO/TiO2 ratios than those from the lower horizons and are close to those of average shales and marine sediments. Moreover, these samples show no or slight negative Ce anomaly. The upper horizon bedded cherts, therefore, deposited in an environment with little contribution of Fe-Mn precipitate from hydrothermal emanations. Accordingly, the hydrothermal effect observed in the bedded cherts under consideration is inferred to have weakened drastically in a short period of time (about 5 m. y.).

Key words : Shimanto terrane, Bedded cherts, Normal paraffin, Major element, Rare earth element   





山本鋼志
・田中 剛・川邊岩夫ほか (1998) 愛知県豊田市北東部の領家花崗岩地域の地球化学図. 地質学雑誌, 104, 688-704.

   We started a study of geochemical mapping in 1994, in order to make environmental assessment of the area around Toyota and Seto Cities, Aichi Prefecture, central Japan. In 1997, new 101 stream sediments were collected in the northeastern part of Toyota City where Cretaceous granitic basements are widely distributed. The collected samples were analyzed for 16 elements (Al,
Ca, Ce, Co, Cr, Cu, Fe, K, Mn, Mg, Na, Ni, P, Sr, Ti, and V) by atomic absorption spectrometry and inductively-coupled plasma atomic emission spectrometry. Sixteen selected samples were analyzed for major elements by X-ray fluorescence spectrometry, and 34 were mineralogically analyzed by X-ray diffractometer.
   The analyses suggest that the stream sediments sampled from areas with sedimentary rock basement are more enriched in SiO2 than those from areas with granitic basement. The X-ray diffraction results suggest that the SiO2 enrichment is caused by quartz. Stream sediments from the basement of the Obara, Naegi-Agematsu and Inagawa granites differ geochemically with each other. Stream sediments from the Obara granitic area are characterized by enrichment of Fe, Ti, Mg, Ni and others owing to the contribution of mafic minerals such as amphibole. Sediments from the Inagawa granitic area are more enriched in Ca than those from the Naegi-Agematu granitic area; enrichment of plagioclase in the former compared to the latter is suggested by X-ray diffraction. The Inagawa granite can be classified into three types on the basis of relative abundances of Ca, Na and K in the stream sediments. The result of this classification is different from that of the previous classification by geological and
petrochemical methods.
   Geochemical maps around Seto and Toyota Cities were presented on the basis of geochemical data of 500 stream sediments. Obvious anthropogenic contamination is not detected in the area, excepting Fe enrichment around a golf
course.

Key words: Environmental assessment, Geochemical map, Stream sediments, Aichi Prefecture, Toyota City, Ryoke granites





山本鋼志・森下泰成  (1997) 蛍光X線分析用微量元素標準試料の調整. 地質学雑誌, 103, 1037-1045.

 Synthetic standards were prepared for the determination of 12 trace elements (Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Ba, Pb and Th) by X-ray fluorescence. Pure chemical reagents of elements of interest were mixed with major-element composites with similar chemical composition to the anorthite-diopsite eutectic mixture. The mechanically mixed standards were melted in an electric heater at about 1400C for the complete homogenization and subsequently quenched in distilled water. The quenched glasses were analyzed by an electron probe microanalyzer (EPMA). Except for CaO, the analytical values gave a good agreement with values calculated by weight of used chemical reagent within the error range of EPMA. The glasses were pulverized and mixed with standard rock samples issued by Gological Survey of Japan to make the variation of major-element composition wider. Synthesized standards range from 43.81 to 73.69% for SiO2 and from less than 10 to about 600ppm for most trace elements. The fusion technique with the mixture of sample and flux (Li2B4O7) in the proportion of 1:2 was applied to the analysis. Precision of calibration curves, corrected for matrix effect by iron content, is high enough to analyze trace elements of concentration above 10ppm in igneous and sedimentary
silicate rocks.

Key words: XRF, X-ray fluorescence, trace element, standard




山本鋼志  (1984) 静岡県西部瀬戸川帯の酸性凝灰岩および珪質泥岩の地球化学的研究. 地質学雑誌, 90, 479-496.

   Nineteen acidic tuffs and 15 interbedded siliceous shales of the Setogawa Terrane in the western part of Shizuoka City, central Japan, were analyzed for 15 major and 15 minor components. The tuffs are enriched in SiO2 and are very hard. The results were compared with those of volcanic materials as well as biogenic bedded cherts for finding geochemical criteria for the examination of origins of siliceous rocks. The following conclusions were obtained by this comparison. I ) Correlation between SiO2 and the other elements in siliceous shales is identical with that in biogenic bedded cherts and shale parphgs. This evidence shows that siliceous shales can be regarded as mixtures of terrigenous clays and silica derived mainly from siliceous organic remains. Whereas, the correlation found in acidic tuffs is different from that in siliceous shales but similar to that in volcanic ashes and tuffs from various regions in the world. The characteristic correlation found in each siliceous rock and volcanic material shows that the their origins can be distinguished by their chemical compositions. 2) SiO2/TiO2-Al2O3/TiO2 and SiO2/TiO2-Na2O/TiO2 diagrams can be useful for distinguishing origins of siliceous rocks. A ternary diagram of 50 x K2O-Rb-Zr is also useful for the same purpose.
   Moreover, in order to examine depositional environments of silica-rich rocks of the Setogawa Terrane, the analytical data of siliceous shales were compared with those of recent argillaceous sediments from various marine environments. This comparison on the basis of MnO and Co values normalized to TiO2 suggests that the siliceous shales are considered to have been formed in nearshore environments or marginal sea. Perhaps the same holds true for the acidic tuffs closely associated with the siliceous shales.
   Whether or not these results can be generally applied to other different siliceous rocks of unknown origins, is not clear at present, but it is emphasized that the geochemical approach exemplified by the present investigation is efBcient in examination of the origins of siliceous rocks.




山本鋼志  (1983) 岐阜県上麻生付近の三畳系層状チャートの地球化学的研究. 地質学雑誌, 89, 143-162.

   Radiolarian bedded cherts and their associated rocks from Kamiaso, Gifu Prefecture, Central Japan, were analyzed and their results were compared with the chemical composition of modern marine sediments from various environments such as near-shore, marginal sea and pelagic in order to deduce the depositional environment of the bedded cherts. Seventy-one chert samples, 42 shale samples interbedded with cherts and 15 siltstone sampls overlying the bedded chert sequence were collected and 15 major and 15 minor components were analyzed by the X-ray fluorescence method. The main conclusions deduced from these data are summarized as follows.
1) Cherts and shale partings show little stratigraphic variations of MnO/TiO2 and Zn/TiO2 ratios in the bedded cherts.
2) Red cherts contain more Fe2O3 than other cherts.
3) Correlation between SiO2 and the other components in cherts are remarkably identical with those in shale partings, and this evidence shows that original source of clays and clastics contained in cherts is the same as that of shale partings; the cherts can be, therefore, regarded as a simple mixture of clays and clastics with radiolarian silica.
4) Each component in the samples was normalized by the TiO2 concentration in the sample. This procedure of TiO2 normalization is useful for the comparison of cherts with marine argillaceous sediments, because this normalized values can represent the composition of clays and clastics in cherts independent of SiO2 contents.
5) Al2O3/TiO2 ratio, Zr/TiO2 ratio and several elements, which are immobile during sedimentation processes, remain nearly constant among cherts, shale partings and marine sediments. This fact shows that the clays and clastics in them were derived from the same source.
6) Micro-manganese nodules precipitated in pelagic sediments are usually more abundant than those in near-shore ones; accordingly, elements concentrated in the nodules can be an important key to the depositional environment of various sediments. It is deduced on the basis of TiO2 normalized values of MnO and Co of cherts and marine sediments that the bedded cherts under consideration formed in a nearshore or hemipela*'ic environment.
7) Discriminant analysis with the geochemical data also supports the above inference of the origin of the bedded cherts.
8) The MnO/TiO2 ratio of cherts is larger than that of shale partings.

   Whether or not these results can be applied to other bedded cherts in deep oceans as well as geosynclines is not clear at present. Nevertheless, the genesis and depositional environment of bedded cherts are of geological and geochemical significance in the study of ancient geosynclines. The geochemical approach exemplified by the present investigation, which has seldom used is efficient in examination of the depositional environment of bedded cherts.