Major and trace element abundances in <180 and 180-2000μm fractions of stream sediments from the Hii River, Shimane Prefecture, Japan

抄録・要旨

Stream sediments collected from 47 localities in the Hii River of Shimane Prefecture were hand sieved to separate the ＜ 180μm and 180-2000μm fractions．Major and trace compositions of both fractions in each sample were determined by X-ray fluorescence analysis．Elemental abundances contrast significantly between the two size fractions．Average abundances of SiO_2，K_2O，Ba，and Rb are greater in the 180-2000μm 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 normalized distributions to average upper continental crust．The greatest departure from upper continental crust composition is observed in the ＜180μm fraction，with enrichment for several ferromagnesian elements（V，TiO_2，Fe_2O_3t，Sc）and for Zr，Y，and Th．In both fractions，Nb，CaO，Na_2O，Sr，Rb，MgO and Ni are slightly depleted relative to UCC．