Crystal-chemistry of talc: A near infrared (NIR) spectroscopy study

Petit, Sabine; Martin, F.; Wiewióra, Andrzej; Parseval, Philippe de; Decarreau, A.

doi:10.2138/am-2004-2-310

Cited by 97 publications

(99 citation statements)

References 11 publications

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“…6a) are the fundamental OH stretching bands of talc. From the experiments on synthetic talcs by Wilkins and Ito (1967) and the rich collection of Farmer (1974), one of the most recent works on analyses of natural talcs having various compositions was published by Petit et al (2004). Their data are in good agreement with the data on these synthetic talcs and with the simulated spectra of 2:1 trioctahedral minerals of the talc type (Scholtzova et al, 2003).…”

Section: Ir Spectroscopymentioning

confidence: 56%

Talc indices from Boumnyebel (Central Cameroon), physico-chemical characteristics and geochemistry

Nkoumbou¹,

Njopwouo²,

Villièras³

et al. 2006

Journal of African Earth Sciences

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Two talc schist occurrences were discovered in the Boumnyebel area, embedded in the Pan-African mica schist, at the junction between Archean, Eburnean and Neoproterozoic formations in Cameroon. They have been analysed by different techniques such as chemical analyses, XRD, DRIFTS, DTA and TG. The talc schist of the northern deposit contains talc (up to 95 wt%) with chlorite, goethite and lepidocrocite as minor minerals. The talc schist of the southern deposit has up to 88% of talc and is speckled with dark green phenoblasts of amphiboles (coexisting prismatic tremolite and magnesio-riebeckite). Due to its high talc content, the amphibole-free talc schist is economically attractive. Chemical analyses show that most of the rocks consist of SiO 2 , MgO and Fe 2 O 3 , except the sample from the southern deposit that displays some amounts of Al 2 O 3 and CaO. Among trace elements, Ni, Co and Cr are as high as in serpentinized peridotites, and suggest a protolith of ultrabasic nature. Chromium concentration in tremolite reaches 6178 ppm; most of the trace elements (Cd, Cr, Dy, Er, Eu, Ga, Gd, Ho, Lu, Nd, Pr, Sm, Sn, Sr, Tb, Tm, Y, Yb, Zr) are compatible with a tremolite lattice. The regional metamorphism yielded garnet micaschist nappes and thus belongs to the upper greenschist facies. Based on the high talc contents of the rocks and occasional coexisting tremolite and magnesio-riebeckite, the origin of the talc deposits is assigned to a hydrothermal alteration of ultramafic rocks. During the hydrothermal event, the fluid composition changed from silica-rich to lime-rich, but very few trace element contents were affected. Thus the low Rb, Sr, Th, Nb, K, Ta, Y, Zr, Hf, MREE and HREE and high Ni, Cr, Co contents of the rocks point to depleted peridotites (harzburgite-lherzolite) and pyroxenite as protoliths. The hydrothermal alteration is expressed in the positive cerium anomaly accompanied by little LREE enrichment of talc-rich rocks and hornblendite. The studied talc schist deposits and the neighbouring gabbroic and ultramafic rocks may belong to a dismembered Pan-African ophiolite set.

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Section: Ir Spectroscopymentioning

confidence: 56%

Talc indices from Boumnyebel (Central Cameroon), physico-chemical characteristics and geochemistry

Nkoumbou¹,

Njopwouo²,

Villièras³

et al. 2006

Journal of African Earth Sciences

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“…5). Following Petit et al (2004aPetit et al ( , 2004b, the relation between the ν OH wavenumber in MIR and the 2ν OH wavenumbers in NIR is: W ν OH = (0.5 × W 2ν OH ) + 85.6. Consequently, the MIR Fe 3+ 2 -OH vibrations should be expected at about 3573 cm −1 and those of Al 2 -OH 3626 cm −1 , which agrees well with literature (e.g.…”

Section: Nir 2 ν-Oh First Overtone Bandsmentioning

confidence: 99%

“…OH vibrational modes are the most often used as a local probe of the octahedral sheet composition, but lattice bands can also give structural information (Madejová et al, 1994;Petit et al, 1995;Gates, 2005;Petit and Madejová, 2013). For well-crystallized 2:1 type clay minerals, and especially trioctahedral talc (Petit et al, 2004a(Petit et al, , 2004bPetit, 2005), IR spectra are relatively well-resolved because bandwidths are narrow and spectral features can be accurately assigned. For dioctahedral smectites, local disorder and the inclination of the OH vibration cause broadening of absorption bands, resulting in difficulties with assignments.…”

Section: Introductionmentioning

confidence: 99%

Hydrothermal synthesis of dioctahedral smectites: The Al–Fe3+ chemical series. Part II: Crystal-chemistry

Petit

Decarreau

Gates

et al. 2015

Applied Clay Science

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“…Hunt defined the set of bands at around 7875 cm -1 (1.27 μm) as due to the first fundamental overtone of the OH stretching vibration combined with the Al-OH deformation mode [46]. Petit et al attributed bands in the 7000 to 7500 cm -1 region as due to the overtones of MgMg-OH, MgAlOH, AlAlOH fundamental OH stretching vibrations [47]. If Fe is also present additional bands are observed.…”

Section: Resultsmentioning

confidence: 99%

Near-infrared spectroscopy of natural alunites

Frost

Wain

2008

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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Near-infrared spectroscopy (NIR) has been used to analyse alunites of formula K(Al 3+ ) 6 (SO 4 ) 4 (OH) 12 . Whilst the spectra of the alunites show a common pattern differences in the spectra are observed which enable the minerals to be distinguished. These differences are attributed to subtle variations in alunite composition. The NIR bands in the 6300 to 7000 cm -1 region are attributed to the first fundamental overtone of both the infrared and Raman hydroxyl stretching vibrations. A set of bands are observed in the 4700 to 5500 cm -1 region which are assigned to combination bands of the hydroxyl stretching and deformation vibrations. NIR spectroscopy has the ability to distinguish between the alunite minerals even when the formula of the minerals is closely related. The NIR spectroscopic technique has great potential as a mineral exploratory tool on planets and in particular Mars.

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Crystal-chemistry of talc: A near infrared (NIR) spectroscopy study

Cited by 97 publications

References 11 publications

Talc indices from Boumnyebel (Central Cameroon), physico-chemical characteristics and geochemistry

Talc indices from Boumnyebel (Central Cameroon), physico-chemical characteristics and geochemistry

Hydrothermal synthesis of dioctahedral smectites: The Al–Fe3+ chemical series. Part II: Crystal-chemistry

Near-infrared spectroscopy of natural alunites

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