Structural Iron in Kaolinites and in Associated Ancillary Minerals

Jepson, W. B.

doi:10.1007/978-94-009-4007-9_15

Cited by 38 publications

(34 citation statements)

References 44 publications

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“…Degradation of kaolinite structure accompanied by partial introduction of Fe 3+ in octahedral positions was observed during tropical weathering in lateritic profiles (Nahon 1981;Jepson 1988). Degraded kaolinite with Fe 3+ within octahedra was encountered during the initial stages of transformation, observed within Recent grains with a rather negligible content of Fe 2 § For more developed phases of transformation, observed here within Miocene grains, Fe e+ prevailed over Fe 3 § and the Mg content was also high (Table 3).…”

Section: Discussion and Conclusion Environmental Factorsmentioning

confidence: 70%

Characterization and Origin of 1:1 Phyllosilicates within Peloids of the Recent, Holocene and Miocene Deposits of the Congo Basin

Wiewióra

Łącka

Giresse

1996

Clays and clay miner.

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Abstract--The grey-green peloids from the Miocene period to Recent fine-grained deposits on the continental shelf close to Congo-Zalre River mouth were studied by X-ray transmission diffractometry (XRD), SEM and by EDAX. The peloids have multiphase heterogenous mineral composition. Their most important constituents are detrital minerals like kaolinite, quartz, goethite, 7 A phases with d(001) ~ 7.3 ,~, and in more maturated grains--nontronite. The d(060) values were used to estimate the general composition of phyllosilicate phases to compare with the composition determined by EDAX. It has been found that d(060) equal to 1.504 ~, is common for Fe3+-bearing kaolinite, which is quite abundant for the Recent peloids. The d(060) equal to 1.535 ,~ and 1.55 A is characteristic for the di-trioctahedral and trioctahedral l:l phases, which are abundant within the more evolved Miocene peloids. Nontronite is characterized by d(060) equal to 1.524 A within concordance with its highly ferrous composition, and partly by its potassic interlayer. It shows cabbage-like nannostructures proving neoformational origin of this mineral in the marine environment.It has been shown that areas of the low sedimentation rate within the Congo Basin were favorable for the mineral changes and neofolrnation. For the Holocene vertical profile, we observed levels of slower sedimentation rates. The evolution is expressed by the disappearance of kaolinite at the expense of other 7 A phases and nontronite. Although more advanced stages of maturation of the studied phases were observed in older peloids (10 4 to l07 y), One cannot detect a linear relationship of these processes with burial.

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Section: Discussion and Conclusion Environmental Factorsmentioning

confidence: 70%

Characterization and Origin of 1:1 Phyllosilicates within Peloids of the Recent, Holocene and Miocene Deposits of the Congo Basin

Wiewióra

Łącka

Giresse

1996

Clays and clay miner.

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“…Most Fe-rich kaolinite flakes are Mg-free and differ from kaolinite only in Fe content. A relatively high iron content (0.6 to 1.0 cation per formula unit) may suggest that Fe-kaolinite originates from continental ferrallitic soils (Herbillon et al, 1976;Mestdagh et al, 1980;Nahon, 1981;Jepson, 1988;Stucki, 1988;Muller and Calas, 1993;Malengreau et al, 1994).…”

Section: Crystallochemical Markers Of Alteration and Neoformation Promentioning

confidence: 99%

Crystal Chemistry of Layer Silicates of the Miocene Green Grain (Congo Basin) from Transmission Electron Microscopy (TEM) and Analytical Electron microscopy (AEM) Observations

Wiewióra

Giresse

Jaunet

et al. 1999

Clays and clay miner.

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Abstract--Transmission electron microscopy (TEM) and analytical electron microscopy (AEM) methods were used to study the crystal chemistry of phyllosilicates occurring in green grains of Miocene sediments from the Congo continental shelf. Using diagrams based on wt. % K and the (Fe + Mg)/A1 ratio, minerals were distinguished from mixed-layer phases. The most abundant detrital mineral is Fe-kaolinite. The morphology and composition identify this mineral as a component of ferralitic soils. This Fe-rich kaolinite has undergone a complex process of partial dissolution and recrystallization and further enrichment in Fe and, to a lesser extent, in Mg in the marine environment. The detrital mica observed with TEM retains the original morphology and chemistry of muscovite. Alteration processes resulted in the crystallization of 1:1 trioctahedral Fe 2+ and Mg-rich minerals and interstratified phases with 1:1 and 2:1 layers in varying proportions observed with the aid of hi~h-resolution transmission electron microscopy (HRTEM) imaging. Included among the newly formed 7-A phases are those apparently containing excess Si. The smectites are apparently neoform, and chemical analyses showed that these marine K-smectites belong to the beidellite-nontronite series and have tetrahedral substitutions similar to muscovite. Their compositions are closer to beidellite than to nontronite, although the latter was observed in association with goethite. The TEM observations and crystallochemical data show that mineral alteration ceased after forming mixedlayer minerals, and alteration did not reach the glauconitization stage. Apparently, the Miocene assemblages experienced rapidly changing environmental conditions and high sedimentation rates that continue today.

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“…Using oxalic acid, the dissolved iron can be precipitated from the leach solution as ferrous oxalate, which can be re-processed to form pure haematite by calcinations [6]. Many researchers have studied the use of oxalic acid to dissolve iron oxide on a laboratory scale [7][8][9][10][11][12][13]. Lee et al [14] used 0.19-0.48M oxalic acid to dissolve hydrated iron oxide.…”

Section: Introductionmentioning

confidence: 99%

Model for Predictive Analysis of Heat Absorbed by Oxalic Acid Solution Relative to the Solution Temperature during Leaching of Iron Oxide Ore

Nwoye¹,

Nwobodo²,

Nlebedim³

et al. 2009

JMMCE

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Structural Iron in Kaolinites and in Associated Ancillary Minerals

Cited by 38 publications

References 44 publications

Characterization and Origin of 1:1 Phyllosilicates within Peloids of the Recent, Holocene and Miocene Deposits of the Congo Basin

Characterization and Origin of 1:1 Phyllosilicates within Peloids of the Recent, Holocene and Miocene Deposits of the Congo Basin

Crystal Chemistry of Layer Silicates of the Miocene Green Grain (Congo Basin) from Transmission Electron Microscopy (TEM) and Analytical Electron microscopy (AEM) Observations

Model for Predictive Analysis of Heat Absorbed by Oxalic Acid Solution Relative to the Solution Temperature during Leaching of Iron Oxide Ore

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