Characterization of a Fine-Grained Interstratification of Turbostratic Talc and Saponite

Annett Steudel,Ulrich Sohling,Friedrich Ruf,Frank Friedrich,Rainer Schuhmann,Katja Emmerich

doi:10.3390/min7010005

Annett Steudel, Ulrich Sohling + Show 4 more

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https://doi.org/10.3390/min7010005

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Abstract

Interstratifications of talc and trioctahedral smectites from different provenances are used as indicators for geological environments and for geotechnical and technical applications. However, comprehensive layer characterization of these interstratifications is rare. Sample EX M 1694, a clay with red-beige appearance from the Madrid basin was studied by X-ray diffraction analysis, X-ray fluorescence analysis, Fourier transformation infrared spectroscopy, simultaneous thermal analysis, gas adsorption measurements, cation exchange capacity, and environmental scanning electron microscopy. More than 95% of particles in EX M 1964 belong to the clay fraction <2 µm. It contains 75% interstratification of 30% turbostratic talc, and 70% saponite type III and 25% turbostratic talc. The turbostratic talc(0.3)/saponite interstratification is characterized by a low number of layers per stack (3), small lateral dimension of layers (60–80 nm) and, accordingly, a high specific surface area (283 m2/g) with nearly equal surface area of micro- and mesopores. Thus, the studied material can be used as mined for adsorption, in contrast to acid-treated clays that produce hazardous waste during production. Low particle size of the interstratification drastically reduced thermal stability and dehydroxylation was superimposed by recrystallization of high temperature phases already at 816 °C, which is low for trioctahedral 2:1 layer minerals.

Highlights

Interstratifications of talc and trioctahedral smectite layers are formed as an abundant mineral in lake and/or spring deposits of Miocene to Pleistocene age and in serpentinized rocks formed by a transformation of ultramafic rocks at low temperature
Stacks of turbostratic talc contain less than 4–5 layers and show broad basal reflections with an increased basal spacing of about 0.96 ± 0.005 nm compared to talc (0.936 nm; [13])
Discussion was used to determine the range of square length (L) of the particles and layer (n) per stack [35,36,37]

Summary

Introduction

Interstratifications of talc and trioctahedral smectite layers are formed as an abundant mineral in lake and/or spring deposits of Miocene to Pleistocene age and in serpentinized rocks formed by a transformation of ultramafic rocks at low temperature.Turbostratic talc/trioctahedral smectite interstratifications occur, for example, in the ProvinceParma (Italy) [1], in the Armagosa Desert (Nevada) [2], and in the Madrid basin (Spain) [3,4,5,6], which is the most extensive studied locality. Turbostratic talc/trioctahedral smectite interstratifications occur, for example, in the Province. Stacks of turbostratic talc contain less than 4–5 layers and show broad basal reflections with an increased basal spacing of about 0.96 ± 0.005 nm compared to talc (0.936 nm; [13]). In the talc structure the oxygen atoms of adjacent layers are partially packed together, thereby, the layers are close together. The sum of the basal reflection of talc 0.936 nm plus 0.027–0.029 nm due to disorder, gives 0.963–0.965 nm, which corresponds with the observed spacing of turbostratic talc [7]. Turbostratic talc is supposed to hold additional water in the structure, which is probably mainly surface-held water [7]

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