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The Mesopotamian Geochemical researches..
THE
IDENTIFICATION AND CHARACTERIZATION OF IRON OXIDE PHASES
IN GA'ARA FORMATION AFTER TREATING WITH NaOH
K.T.
AL-YOUZBAKEY
kotayba_tawfiq@yahoo.com
Saddam Research
Center for Dams and Water Resources
University
of Mosul.
Iraqi
Geological Journal, 27(3)» pp.
130-151, (1994)
Abstract
The identification and characterization of goethite and hematite in
kaolinitic clayetones are like to be simple after
concentrated iron oxides by treating with NaOH.
The Al substitutions displays 2 to 13 mole% for goethite and
1 to 7 mole% for hematite. In general the ratio
of Al substitutions in hematite and goethite were around
0.5:l. Al substitution in both minerals cause shortening
in the unit cell dimensions (b Ao and
c A° dimension in goethite and a A0
dimension in hematite). The mean crystalline dimensions
indicated a growth in the Z direction for goethite
crystals (as an acicular habits) and a development in
the X-Y plane for hematite crystals (as a platy nature).
Fe-oxalate / Fe-HCl ratio was used as a measure of
crystallinity, it reflects high crystalline iron oxides
and low amorphous materials. Hematite present in the
studied samples is relatively small amount compared with
goethite, the hematite/goethite ratio was measured by
the X-ray diffraction lines intensities as I(102)hem.
/I(110)goe..
The results of Infrared and X-ray diffraction analyses had been
went concordantly in Al substitution. Both bands δOH (at
896 cm-1) and γOH (at 789 cm-1)
were sensitive to Al substitution in goethite, whereas
(530 cm-1) and (458 cm-1) were
sensitive to Al in hematite, therefore, they were used
to estimate the amount of Al substitutions. The Infrared
absorption intensities for the two strongest bands at
890 cm-1 and 790 cm-1 were related
to the degree of crystallinity. The I896/I798
ratio were decreases as the crystallinity increases.
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