@article{oai:nagoya.repo.nii.ac.jp:00001419,
 author = {Tanaka, Tsuyoshi and Kawabe, Iwao and Yamamoto, Koshi and Iwamori, Hikaru and HIRAHARA, Yasuhiro and MIMURA, Koichi and ASAHARA, Yoshihiro and MINAMI, Masayo and ITO, Takamori and DRAGUSANU, Cristian and MIURA, Noriko and AOKI, Hiroshi and OHTA, Atsuyuki and TOGAMI, Kaoru and TORIUMI, Takahiro and MATSUMURA, Yoko and SAKAKIBARA, Tomoyasu and TANIMIZU, Masaharu and MIZUTANI, Yoshikazu and MIYANAGA, Naozumi and MURAYAMA, Masaki and TAKAYANAGI, Yukio},
 journal = {The Journal of earth and planetary sciences, Nagoya University},
 month = {Dec},
 note = {Our study of geochemical mapping in the area of Toyota and Seto Cities, Aichi Pref., central Japan, has been further extended. This geochemical mapping, started in 1994 for the purpose of environmental assessment of this area, is based on chemical data of stream sediments of drainage systems distributed over the area. Cretaceous granitic basements occur widely in the eastern part, whereas late Cenozoic sedimentary rocks cover the basements in the western part. In 1996,we have extended the mapped area to the northeastern part of Toyota City, and collected new 66 samples. Since 1994,we have sampled stream sediments from 352 different locations in the area of approximately 25 km × 25 km. All the samples have been analyzed for Al, Ti, P, Ni, Co, V, Sr, Cu, Cr, Ce and Zn by ICP-AES and for K, Na, Fe, Ca, Mg and Mn by AAS. In addition, representative samples of three different types of Cretaceous granites and their biotite mineral separates were analyzed. It turned out that chemical compositions of stream sediments in the areas of Creataceous granitic basements are systematically different from those in the areas of sedimentary rocks : (1) The Ca/Ti ratio and Ca, Na and Sr abundances in Cretaceous granitic basements are higher than those in the areas of the sedimentary rocks. (2) Cr, Co, Cu, Ni, V and Zn are depleted in the stream sediments from the granitic basements relative to the sedimentary rock areas. (3) The areal distribution patterns of the Ca/Ti ratio and the elemental abundances coincide with the distribution of the Cretaceous granitic basements. The geochemical results are fairly reasonable, because the sedimentary rocks have experienced much more intensive weathering reactions than the Cretaceous granitic rocks. During weathering of granitic rocks, plagioclase is more readily decomposed than biotite. Hence, as the weathering proceeds, the abundance of biotite relative to plagioclase increases in weathered rocks. As a result, the clastic materials transported into sedimentary basins tend to be depleted in Ca, Sr and Na because these cations are contained mainly in plagioclase. But such clastics become enriched in Ti, Cr, Co, Cu, Ni, V and Zn because biotites still accommodate these cations. This inference is consistent with our analyses of representative samples of granites and their biotite mineral separates. The areal distribution of Ce, however, does not show such a systematic difference between the two geologically different areas. Finer grains of Ce-rich rare phases such as monazite, allanite and/or sphene may be responsible for the areal distribution pattern of Ce abundance in the stream sediments., 国立情報学研究所で電子化したコンテンツを使用している。},
 pages = {27--47},
 title = {Geochemical mapping of the northern area of Toyota City, Aichi Prefecture, central Japan : Distinct chemical characteristics of stream sediments between granitic and sedimentary rock areas},
 volume = {43},
 year = {1996}
}