Dynamic recrystallization and fabric development during the simple shear deformation of ice     

J.P Burg  C.J.L Wilson  J.C Mitchell 《Journal of Structural Geology》1986,8(8)

In situ observations of polycrystalline ice deformed in simple shear between −10 and −1°C are presented. This study illustrates the processes responsible for the deformation, the development of a preferred crystallographic orientation and the formation of a preferred dimensional orientation. Intracrystalline glide on the basal plane, accompanying grain rotations and dynamic recrystallization, helps to accommodate the large intragranular strains. These are the most important mechanisms for crystallographic reorientation and produce a stable fabric that favours glide on the basal plane. Localized kinks, developed in grains unfavourably oriented for easy glide, are unstable and are overprinted by dynamic recrystallization. Dynamic recrystallization is a strain softening process with nucleation occurring in the form of equiaxed grains that grow subparallel to pre-existing grain anisotropies and become elongate during deformation. Plots of grain axial ratio against orientation ( ) indicate a weak shape fabric which does not correspond to the theoretical foliation and elongation for the appropriate increment of shear strain. We argue that estimates of the strain magnitude made from orientation of elongate grains are unreliable in high temperature shear zones. These results are applicable to both geological and glacial shear environments.  相似文献   

Tension fractures and boudinage oblique to the maximum extension direction: an analogy with lüders' bands     

J.P. Burg  L.B. Harris   《Tectonophysics》1982,83(3-4)

A study has been made of the orientation of boudin necklines and extension fractures with respect to the maximum extension direction X determined by infilling fibre growth. Several localities, within the Variscan belt of Western Europe, the Pyrenees and the Alps, have been investigated in detail. It has been generally accepted that boudinage and extension fracturing occur perpendicular to X in the rock at the time of their formation; however, we have shown that is not the case: boudin necklines and extension fractures occur at an angle between 45°–90° to X, with the most frequent orientations between 65°–70° and 80°–85°. Angles of exactly 90° are rare.In order to explain · this obliquity, an analogy is made with the phenomenon of Lüders' bands (localised regions of plastic deformation) developed in thin metal plates under tensile testing. Because the thickness of a layer is negligible compared with its lateral extent, we will only be concerned here with the case of thin metal plates.  相似文献   

Combined thrusting and wrenching in the Ibero-Armorican arc: A corner effect during continental collision   总被引：1，自引：0，他引：1  

Jean-Pierre Brun  Jean-Pierre Burg 《Earth and Planetary Science Letters》1982,61(2):319-332

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Metamorphic conditions and structural evolution of the Kesebir-Kardamos dome: Rhodope metamorphic complex (Greece-Bulgaria)     

Moulas  Evangelos  Schenker  Filippo Luca  Burg  Jean-Pierre  Kostopoulos  Dimitrios 《International Journal of Earth Sciences》2017,106(8):2667-2685

International Journal of Earth Sciences - The synmetamorphic nappe system of the Rhodope Metamorphic Complex has been deformed into dome-and-basin structures attributed to syn- to post-convergent...  相似文献