Cessation of plastic deformation during exhumation of metamorphic tectonites revealed by microboudinage structures

Masuda, Toshiaki; Kimura, Nozomi; Okamoto, Atsushi; Miyake, Tomoya; Omori, Yasutomo

doi:10.1016/j.jsg.2006.06.019

Cited by 8 publications

(2 citation statements)

References 22 publications

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“…5). Given that the microboudinage is considered to have occurred immediately before the rock entered the brittle-plastic transition from the plastic realm (e.g., Masuda et al, 2007Masuda et al, , 2011, the estimated value should reflect the state of differential stress corresponding to the last stage of plastic deformation.…”

Section: Discussionmentioning

confidence: 99%

The relationship between the proportion of microboudinaged columnar grains and far–field differential stress: A numerical model for analyzing paleodifferential stress

Matsumura

Kuwatani

Masuda

2017

Journal of Mineralogical and Petrological Sciences

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Microboudin paleopiezometry is an intensive endeavor that involves measurement of several hundred grains per sample to produce reliable estimations of far-field differential stress. This procedure is particularly time-consuming when conducting stress analysis for a large number of samples within a metamorphic belt. To improve and expedite the stress estimation procedure, we propose a numerical model that uses grain-shape data to calculate the relationship between the proportion of microboudinaged columnar grains ( p) and the far-field differential stress (σ 0 ). Our model combines the weakest link theory and the shear-lag model. The weakest link theory is used to derive the fracture strength of grains, whereas the shear-lag model is used to determine the relationship between the differential stress within a grain (σ) and σ 0 . An intact grain becomes a microboudinaged grain when σ is higher than its fracture strength at a specific point within the grain. Here, we make calculations of p for all intact grains under increasing σ 0 from 0 to 20 MPa. Our calculations show that the modeled and observed distributions of p and the aspect ratio have similar patterns for both intact and microboudinaged grains. The value of p increases with increasing σ 0 , with 70% of the grains being microboudinaged when σ 0 = 20 MPa. These results suggest that our model is capable of reproducing observed data for microboudinaged columnar grains and that the relationship between p and σ 0 can be used to estimate the magnitude of differential stress without the need to measure grain-size data for several hundred grains with a wide range of aspect ratios.

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Section: Discussionmentioning

confidence: 99%

The relationship between the proportion of microboudinaged columnar grains and far–field differential stress: A numerical model for analyzing paleodifferential stress

Matsumura

Kuwatani

Masuda

2017

Journal of Mineralogical and Petrological Sciences

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“…Boudinage and folding Orientation and shape of boudinage are useful in kinementic analysis of deformed rocks particularly in paleostrain analysis (e.g., Ramsay 1967;Ferguson 1981;Lloyd and Ferguson 1989;Lloyd et al 1982;Ramsay and Huber 1983;Masuda et al 1995;Akawy 1999;Masuda et al 2007). In the study area, simple boudinage is common while the composite one is rare.…”

Section: Strain Analysismentioning

confidence: 99%

Structural elements and incremental strain history of the basement rocks of Um Had area, central Eastern Desert, Egypt

Akawy

2009

Arab J Geosci

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The Um Had area, central Eastern Desert, Egypt shows a regional stretching in the NW-SE and a contraction in the NE-SW direction. Major NW-SE folds, small recumbent folds, and local thrusts and reverse faults were recognized. Complicated relation between folds and boudinage was identified. This stretching amount ranges from 1.282 to 1.309. Earlier coaxial and later non-coaxial strains were inferred. The change from axial to non-coaxial stress regime was gradual and the latter was associated with minor clockwise and anticlockwise rotation of structural elements. During the non-coaxial strain, strain fringes were formed as a consequence of the high circulation of fluids in low temperature and high pressure conditions. Superimposed strain fringes indicating right-and left-lateral senses of movement were recognized. At least three generations of fringes were recognized, implying three stages of non-coaxial stretching. Each generation has about 15 increments which show irregular strain gradient and intensity over the different increments. Eastwards, the strain increments became mature and westwards, the finite strain increases. The strongest finite strain was found in a narrow belt delimiting the basement rocks on the west and underlying the Phanerozoic sediments. Chocolate-tablet structure was recorded and indicates later multidirectional tension. Not all Nubia Sandstone exposures are overlying the basement rocks and some are separated by NW-SE normal faults. Major NW-SE normal faults are cutting basement rocks of different ages.

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Determination of amphibole fracture strength for quantitative palaeostress analysis using microboudinage structures

Kimura

Nakayama

Tsukimura

et al. 2010

Journal of Structural Geology

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Cessation of plastic deformation during exhumation of metamorphic tectonites revealed by microboudinage structures

Cited by 8 publications

References 22 publications

The relationship between the proportion of microboudinaged columnar grains and far–field differential stress: A numerical model for analyzing paleodifferential stress

The relationship between the proportion of microboudinaged columnar grains and far–field differential stress: A numerical model for analyzing paleodifferential stress

Structural elements and incremental strain history of the basement rocks of Um Had area, central Eastern Desert, Egypt

Determination of amphibole fracture strength for quantitative palaeostress analysis using microboudinage structures

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