Beschreibung:
<jats:p>Abstract. The OH stretching vibrational properties of eight
serpentine samples from veins of the New Caledonian ophiolite have been
investigated by Fourier-transform infrared spectroscopy (FTIR) in the mid-infrared
and near-infrared ranges and by Raman spectroscopy. The samples were
selected for their monophasic composition (Lz: lizardite; Ctl: chrysotile;
and Atg: antigorite) making them representative of the three serpentine
species. Comparison of fundamental and overtone spectra allowed us to interpret
most of the observed bands and to propose consistent spectral decomposition
in individual components. The OH stretching bands related to intrinsic
vibrational properties of the minerals are distinguished from those
associated with chemical substitutions in octahedral sites (mainly Fe and Ni
for Mg substitutions). Observations made on the most symmetric Lz are
consistent with previous interpretations and underline the effect of
macroscopic parameters on OH stretching bands in the FTIR spectra. The major
importance of the distribution of OH bond lengths in the broadening of the
vibrational signals of the less symmetric and more distorted Atg is
confirmed. The combination of the three spectroscopic methods makes it
possible to unravel the occurrence of two different types of interlayer OH
environments in Ctl nanotubes. One corresponds to the features observed at
3684 and 7171 cm−1 in the fundamental and overtone spectra,
respectively, and is similar to the local OH environment observed in Lz. The
other corresponds to broader signals observed at 3693 and 7200 cm−1 in
the fundamental and overtone spectra, respectively. It reflects a
distribution of OH bond lengths likely related to local structural misfits
between adjacent layers in the tubular structure of Ctl.
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