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A Study on the Formation of Smectite in Silica Scales Precipitated from Geothermal Water: The Effect of Magnesium
Author(s) -
Aramaki Yoshinobu,
Yokoyama Takushi,
Okaue Yoshihiro,
Imai Akira,
Watanabe Koichiro
Publication year - 2005
Publication title -
resource geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 43
eISSN - 1751-3928
pISSN - 1344-1698
DOI - 10.1111/j.1751-3928.2005.tb00248.x
Subject(s) - clay minerals , magnesium , geothermal gradient , mineralogy , nmr spectra database , chemistry , geology , spectral line , organic chemistry , physics , astronomy , geophysics
. Silica scales containing large amounts of smectite were recently found in the pipelines for geothermal water at a geothermal power plant. To elucidate the mechanism of smectite formation, seven silica scale samples were characterized by powder X‐ray diffraction, chemical analysis and 27 A1 MAS NMR. Smectite was present in samples with MgO levels above 10 wt% and Al 2 O 3 levels below 10 wt%. In 27 A1 MAS NMR spectra, peaks assigned to both tetrahedrally and octahedrally coordinated aluminum (Al(4) and Al(6)) were observed for Mg‐rich samples, whereas a peak due to Al(4) alone appeared in Mg‐poor samples. From these observation and comparison between 27 A1 MAS NMR spectra for synthesized precipitates of Al 2 O 3 ‐SiO 2 containing MgO and not containing MgO, it is concluded that magnesium plays an important role in the stabilization of Al(6), and results in the formation of smectite