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Preferred orientation in experimentally deformed dolomite

✍ Scribed by H. -R. Wenk; J. Shore


Publisher
Springer
Year
1975
Tongue
English
Weight
784 KB
Volume
50
Category
Article
ISSN
0010-7999

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✦ Synopsis


Fine grained dolomite has been deformed in over twenty compression experiments in a Griggs-type piston-cylinder apparatus at various P and T conditions. Preferred orientation determined quantitatively using X-ray techniques and spherical harmonic analysis of the data is presented in inverse pole-figures of 3 2/m symmetry. In most cases specimens display strong preferred orientation which varies mainly as a function of temperature. At all conditions it is very different from ealcitic limestone. Although there is no significant grain growth even at 1000 ~ C the simple c-axes maximum fabric above 700 ~ C might be the result of recrystallization or translation on c. Below 700 ~ C, the preferred orientation is much weaker and complex. The primary maximum in the inverse pole-figure is near e, a secondary maximum near a high angle positive rhomb, principal minima are at c and f. This inverse pole-figure is consistent with ]-twinning and translation gliding on r (t=a?), two mechanisms which counteract each other. The latter is a new deformation mechanism for dolomite which we propose in order to explain the pattern of preferred orientation. The minimum at c is less pronouneed below 100 ~ C suggesting that c-translation may be active, but in these fine-grained aggregates it appears to be less important than is expected from single crystal experiments (Higgs and tIandin, 1959), at least at low temperatures.


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