Publication Date:
2016-05-03
Description:
The full elastic tensors of two K-rich monoclinic alkali feldspars, Or 83 Ab 15 sanidine and Or 93 Ab 7 orthoclase, have been determined by using the Impulse Stimulated Light Scattering technique to measure surface acoustic wave velocities. The new data confirm that alkali feldspars exhibit extreme elastic anisotropy, so the bounds of their isotropic average properties span a wide range. The measured adiabatic moduli are, for Or 83 Ab 15 and Or 93 Ab 7 , respectively, K Reuss = 54.7(7), 54.5(5) GPa; K Voigt = 62.9(1.1), 64.4(0.6) GPa; G Reuss = 24.1(1), 24.5(1) GPa; and G Voigt = 36.1(5), 36.1(7) GPa. The small differences in moduli between the samples suggests that variations in composition and in state of Al, Si order only have minor effects on the average elastic properties of K-rich feldspars. The new measurements confirm that the earliest determinations of elastic wave velocities of alkali feldspars, widely used to calculate wave velocities in rocks, resulted in velocities systematically and significantly too slow by 10% or more.
Print ISSN:
0003-004X
Electronic ISSN:
1945-3027
Topics:
Geosciences
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