In the paper “Why calcite can be stronger than quartz” by Neil S. Mancktelow and Giorgio Pennacchioni (Journal of Geophysical Research, 115, B01402, doi:10.1029/2009JB006526, 2010), Figure 10 requires clarification of the parameters used in its calculation to avoid misinterpretation. Figure 10 presents the deformed shapes at shear strain γ = 6 of cylindrical inclusions with an initially circular cross section. The results, calculated by the first author using a personally developed FEM code, were used to demonstrate that for power law materials in simple shear flow, nearly rigid behavior of isolated inclusions is possible even when the effective viscosity ratio is low (~2). In particular, the example with a power law stress exponent of n = 6 in the inclusion and n = 3 in the matrix was considered to be directly relevant to natural examples of coarse calcite clasts in quartz mylonites from the Neves area of the eastern Alps. This fundamental conclusion is correct, as are the calculated shapes for the parameters employed. However, with the aim of remaining concise, details of these parameters were not given: it was simply stated in the caption that “the effective viscosity ratio (μi/μm),” as listed on the left, was “for the case of equal strain rate in inclusion and matrix.” This statement requires clarification because (1) for power law viscous material there is no specific material parameter “viscosity” (or “viscosity ratio”) independent of strain rate, as there is for linear viscous behavior, (2) the strain rate in the inclusion and matrix will not be the same, even at the very start of a numerical experiment, and (3) the strain rate in the inclusion will vary with its axial ratio and orientation.

Correction to "Why calcite can be stronger than quartz"

PENNACCHIONI, GIORGIO
2010

Abstract

In the paper “Why calcite can be stronger than quartz” by Neil S. Mancktelow and Giorgio Pennacchioni (Journal of Geophysical Research, 115, B01402, doi:10.1029/2009JB006526, 2010), Figure 10 requires clarification of the parameters used in its calculation to avoid misinterpretation. Figure 10 presents the deformed shapes at shear strain γ = 6 of cylindrical inclusions with an initially circular cross section. The results, calculated by the first author using a personally developed FEM code, were used to demonstrate that for power law materials in simple shear flow, nearly rigid behavior of isolated inclusions is possible even when the effective viscosity ratio is low (~2). In particular, the example with a power law stress exponent of n = 6 in the inclusion and n = 3 in the matrix was considered to be directly relevant to natural examples of coarse calcite clasts in quartz mylonites from the Neves area of the eastern Alps. This fundamental conclusion is correct, as are the calculated shapes for the parameters employed. However, with the aim of remaining concise, details of these parameters were not given: it was simply stated in the caption that “the effective viscosity ratio (μi/μm),” as listed on the left, was “for the case of equal strain rate in inclusion and matrix.” This statement requires clarification because (1) for power law viscous material there is no specific material parameter “viscosity” (or “viscosity ratio”) independent of strain rate, as there is for linear viscous behavior, (2) the strain rate in the inclusion and matrix will not be the same, even at the very start of a numerical experiment, and (3) the strain rate in the inclusion will vary with its axial ratio and orientation.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2426755
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