instrumental techniques applied to mineralogy and geochemistry
instrumental techniques applied to mineralogy and geochemistry
instrumental techniques applied to mineralogy and geochemistry
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Biliana Gasharova<br />
constitute the main reservoir for water in the Earth’s mantle. Even traces of water in<br />
minerals such as olivine drastically reduce mechanical strength, with major<br />
consequences for mantle convection <strong>and</strong> the formation of minerals as diamonds. The<br />
distribution of H 2 O around inclusions <strong>and</strong> cracks in nominally anhydrous mantle<br />
minerals such as olivine is studied by IR microspectroscopy mapping (Fig. 6, Sommer et<br />
al., 2008).<br />
FIGURE 6. Left: Synchrotron IR spectra of OH stretching b<strong>and</strong>s of olivine in , , directions. The<br />
quantitative analysis of anisotropic minerals involves summing absorption intensities from<br />
polarized spectra. The water content was calculated with the help of the Beer–Lambert law <strong>and</strong> a<br />
calibration after Bell et al. (2003). The absorbance was normalized <strong>to</strong> 1 cm sample thickness. The<br />
water content (normalized in ppm H 2 O by weight) is 138 ppm in the clear, inclusion-free olivine<br />
matrix. Right: 3D graph (40x40 μm 2 ) showing the increase of water <strong>to</strong>wards a <strong>to</strong>tally embedded<br />
Cr-spinel inclusion (5-8 μm in size) in olivine. The H 2 O content significantly increases <strong>to</strong>wards the<br />
inclusion up <strong>to</strong> values of about 800 ppm.
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