伊香保温泉から析出したノントロナイト

概要

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The occurrence of nontronite as hot-spring deposit is first described from Ikaho Hot-springs, Gunma Prefecture, Japan. The hot-spring water, issuing from the No. 6 drilled well (Temp.=65.9℃, pH=6.65) is introduced into a concrete tank, where yellow-green deposit is precipitating with a rate of 1cm /year. The deposit has been identified as nontronite by chemical analysis, thermal analyses (DTA and TG), infrared spectra, and X-ray diffractometry. A typical nontronite sample (No. 6-1-G), with a composition of {Na_<0.02>K_<0.01>Ca_<0.10>} (Fe^<3+>_<1.45>Mn_>0.02>Mg_<0.08)[Si_<3.37>Al_<0.13>Fe^<3+>_<0.50>]O_<10>(OH)_<1.86>. nH_2O. has been revealed by scanning electron microscopy to be an aggregate of small particles with a diameter less than 1〜2μm, and by transmisson electron micrograph to be feathery. This sample is slightly higher in iron content than the idealized formula of nontronite. Moessbauer spectroscopy showed that Fe in the sample is mostly in trivalent state. The genetic condition of this mineral is also discussed.
日本地球化学会の論文
1994-09-10