Iron oxide and clay minerals and their relation to colours of red and yellow podzolic soils near Sydney, Australia

Abstract--Hydrogen-(3D = -106 to -97%0 and oxygen-(3180 = +14.0 to +16.6%0 isotope compositions of kaolinite from late Cretaceous and Oligocene deposits at Iwaizumi, northeastern Japan, indicate that these clays formed by weathering of volcanic parent rocks, rather than during hydrothermal (>100 ~ alteration. The Iwaizumi kaolinites also are depleted of D and 180 relative to kaolinite formed during modern, tropical weathering, suggesting that the kaolinite developed under cool or cool-temperate conditions. The oxygen-isotope compositions of the kaolinite increase slightly upward through the deposits, perhaps implying a modest increase in temperature from late Cretaceous to Oligocene time. The 8D and 8~sO results for kaolinite from the Oligocene deposits closely follow the kaolinite weathering line. However, a small but systematic deviation from this line for the Cretaceous kaolinites is most simply explained by post-formational, hydrogen-isotope exchange between these clays and downward percolating meteoric water.

Section: Introductionmentioning

confidence: 98%

Origin of Cretaceous and Oligocene Kaolinites from the Iwaizumi Clay Deposit, Iwate, Northeastern Japan

Mizota

Longstaffe

1996

“…not et al, 1971;Davey et al, 1975;Nahon et al, 1977;Bigham et al, 1978;Fitzpatrick, 1978;Mendelovici et al, 1979;Torrent et al, 1980;Fitzpatrick and Schwertmann, 1981;K~impf, 1981), oolitic iron ores (Scheiderh6hn, 1964;Schellmann, 1964), and bauxites U6-ntis and Solymfir, 1970). Al-substituted goethites can also be easily synthesized in the laboratory (Thiel, 1963;J6nts and Solymtr, 1970;Golden, 1978;Schwertmann, 1979a, 1979b;Fey and Dixon, 1981).…”

Section: Introductionmentioning

confidence: 99%

The Influence of Aluminum on Iron Oxides. VIII. Unit-Cell Dimensions of Al-Substituted Goethites and Estimation of Al from them

Schulze

1984

355

197

Abstract--The unit-cell dimensions of synthetic, Al-substituted goethites showed that the c dimension is a linear function of A1 substitution in the range 0-33 mole % A1, but that the a dimension is variable over this same range. The b dimension is also linearly related to Al substitution but is slightly more variable than the c dimension for A1 substitutions of 20-33 mole %. The variability of the a dimension is postulated to be the result of structural defects. An improved procedure for estimating Al substitution from x-ray powder diffraction positions requires (1) calculation of the c dimension from the positions of the 1 l0 and 111 diffraction lines using the formula: c = (l/d(11 l) 2 -l/d(110)2) -'h, and (2) estimation of A1 substitution from the relationship: mole % A1 = 1730 -572.0c. The 95% confidence interval of the estimate is +2.6 mole % A1 when using this procedure, in contrast to _+4.0 mole % A1 when the position of the 111 reflection alone is used.

“…In order to concentrate Fe oxides from such materials, Norrish and Taylor (1961) used a boiling 5-MNaOH treatment for kaolinitic-goethitic samples to remove kaolinite and were thus able to determine the degree of A1 substitution of the goethites. Since then, this method has been used only occasionally (Janot et al, 1971;FSlster, 1971;Davey et al, 1975;Resende, 1976;Bigham et al, 1978;Kitagawa and Mrller, 1979;Torrent et al, 1980), perhaps because of the possibility that the rather drastic treatment might alter the Fe oxides with respect to form, crystallinity, and substitution. This possibility was supported by work on synthetic and natural Fe oxides (Kojima, 1963;Petit et al, 1964;Janot et al, 1971) in which transformations and increased crystallinity of goethite were observed.…”

Section: Introductionmentioning

confidence: 99%

The 5-M-NaOH Concentration Treatment for Iron Oxides in Soils

Kämpf

Schwertmann

1982

203

The boiling 5-M-NaOH treatment was found to aid in the identification and characterization of goethite and hematite by effectively concentrating the two Fe oxides in kaolinitic-gibbsitic soil clays. No transformations of goethite to hematite or hematite to goethite were detected, but poorly crystalline, highly Al-substituted goethite was found to dissolve and recrystallize into a more well-crystalline, less Al-substituted goethite in samples low in Si. The Si released from kaolinite was sufficient to block goethite dissolution and recrystallization in kaolinitic samples, but noncrystalline silica had to be added to samples rich in gibbsite to minimize this effect.