M.I. Staid
M.D. Kraft
J. R. Johnson
2007
<p><span>New measurements of </span>thermal<span> </span>infrared<span> emission spectra (250-1400 cm</span><sup>-1</sup><span>; ∼7-40 μm) of </span>experimentally<span> </span>shocked<span> </span>basalt<span> and basaltic andesite (17-56 GPa) exhibit changes in spectral features with increasing pressure consistent with changes in the structure of plagioclase feldspars. Major spectral absorptions in unshocked rocks between 350-700 cm</span><sup>-1</sup><span> (due to Si-O-Si octahedral bending vibrations) and between 1000-1250 cm</span><sup>-1</sup><span> (due to Si-O antisymmetric stretch motions of the silica tetrahedra) transform at pressures >20-25 GPa to two broad spectral features centered near 950-1050 and 400-450 cm</span><sup>-1</sup><span>. Linear deconvolution models using spectral libraries composed of common mineral and glass spectra replicate the spectra of </span>shocked<span> </span>basalt<span> relatively well up to shock pressures of 20-25 GPa, above which model errors increase substantially, coincident with the onset of diaplectic glass formation in plagioclase. Inclusion of </span>shocked<span> feldspar spectra in the libraries improves fits for more highly </span>shocked<span> </span>basalt<span>. However, deconvolution models of the basaltic andesite select </span>shocked<span> feldspar end-members even for unshocked samples, likely caused by the higher primary glass content in the basaltic andesite sample.</span></p>
application/pdf
10.2138/am.2007.2356
en
Walter de Gruyter
Thermal infrared spectroscopy and modeling of experimentally shocked basalts
article