| 1. |
- Alm, Ove, et al.
(författare)
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Experimental deformation of Augen-gneisses
- 1979
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Ingår i: Mechanisms of deformation and fracture. - Oxford : Pergamon Press. - 0080242588 ; , s. 173-186
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Konferensbidrag (refereegranskat)
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| 2. |
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| 3. |
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| 4. |
- Burns, K.L, et al.
(författare)
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The Flinders Ranges breccias of South Australia diapirs or décollement?
- 1977
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Ingår i: Journal of the Geological Society. - : Geological Society of London. - 0016-7649 .- 2041-479X. ; 134:3, s. 363-384
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Tidskriftsartikel (refereegranskat)abstract
- Breccia-cored domes in the Northern Flinders Ranges, South Australia, have been regarded as diapirs analogous to diapiric salt structures in northwestern Germany and the Gulf Coast. It is shown that the core of the Blinman Dome is not intrusive and is not composed of less dense rocks; hence a diapiric process cannot apply. It is suggested that much of the breccia of the core is formed by deformation of a stratigraphic unit composed of interbedded competent and incompetent beds at a Flinders Ranges dgcollernent and results from folding. If this model is correct, the Flinders Ranges structures should occur at ddcollements in other parts of the world.
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| 5. |
- Stephansson, Ove
(författare)
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A Discussion on natural strain and geological structure - Finite element analysis of folds
- 1976
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Ingår i: Philosophical transactions of the Royal Society of London. Series A, Mathematical and physical sciences. - : The Royal Society. - 0080-4614 .- 2054-0272. ; 283:1312, s. 153-161
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Tidskriftsartikel (refereegranskat)abstract
- Finite element analysis of the time-dependent deformations of layered viscous solids serves as the basis of the study of the mechanics of folding. The progressive development of folds by buckling in single and multilayer models compressed parallel to the layering is reviewed. Fold geometries are shown to vary from parallel, for large viscous contrasts, to nearly similar, for low contrasts. For models with the same viscosity contrast the geometry depends upon the wavelength/thickness ratio, so that thin-layer folds behave in the most £ competent5 fashion with a great amount of buckle shortening. The development of stresses around folds is discussed. As the fold grows the principal stresses rotate and the magnitude changes quite drastically for models with high viscosity contrast. These folds also have the gradient of mean stress directed perpendicular to the layer in the hinge part of the competent layer. The heterogeneous stress distribution, as it appears in a fold structure, generates a free energy gradient, and diffusion current will tend to bring the system to a state of equilibrium by one or more of the following events: (1) introduction of new mineral species; (2) polymorphic phase changes; (3) a change in chemical composition and (4) a change in grain size. Future development of the finite element analysis of folding is discussed.
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| 6. |
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| 7. |
- Stephansson, Ove, et al.
(författare)
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Deformation of a jointed rock mass
- 1978
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Ingår i: Geologiska föreningens i Stockholm förhandlingar. - : Informa UK Limited. - 0016-786X. ; 100:3, s. 287-294
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Tidskriftsartikel (refereegranskat)abstract
- The finite-element method and the discrete-block method have been used to study the defor-mational behaviour of a jointed rock mass subjected to simple shear displacement. Blocks in models with large sizes of block make contact at few points which cause large openings of joints and high stress concentrations in the blocks and surrounding joints. The introduction of more joints into the models evens out the forces, reduces the stresses and causes a gentle type of deformation. From this study, we draw the practical conclusion that joints in rock plinths are eligible for the storage of radio-active waste, if we take into account the effect of simple shear displacement from faulting
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| 8. |
- Stephansson, Ove
(författare)
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Granite diapirism in Archaean rocks
- 1977
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Ingår i: Journal of the Geological Society. - : Geological Society of London. - 0016-7649 .- 2041-479X. ; 133:4, s. 357-361
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Tidskriftsartikel (refereegranskat)abstract
- This contribution is an extended abstract of a paper published elsewhere. It is included as an introduction to the published discussion which was stimulated by Professor Stephansson's lecture.
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| 9. |
- Stephansson, Ove, et al.
(författare)
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Pre-holocene joint fillings at Forsmark, Uppland, Sweden
- 1975
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 97:1, s. 91-95
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Tidskriftsartikel (refereegranskat)abstract
- Subhorizontal joints filled with sediments were found at Forsmark in north-eastern Uppland, Sweden. The sediments are glacial in character and show varves, graded and current bedding, and clay laminae. The occurrence, structure and pollen frequency of the sediments imply a deposition during a Pre-Holocene age, possibly during Early or Middle Weichsel.
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| 10. |
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| 11. |
- Stephansson, Ove, et al.
(författare)
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Revben i berg
- 1977
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Rapport (övrigt vetenskapligt/konstnärligt)
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| 12. |
- Stephansson, Ove, et al.
(författare)
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Seismic study of shallow jointed rocks
- 1979
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Ingår i: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts. - : Elsevier BV. - 0148-9062 .- 1879-2073. ; 16:5, s. 319-327
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Tidskriftsartikel (refereegranskat)abstract
- A theory of wave propagation in shallow jointed rocks is presented. The elastic waves from a source are propagated around the tip of an open joint. The depth of the joint is determined from known intercept times, wave velocities and joint spacing. The principles developed in this paper are compared with the theory of seismic refraction, and are verified in model experiments on artificial joints in concrete blocks.Field tests were made in an open pit and an underground mine. An explosive pulse exciter for generation of P- and SH-waves is described. The depth of jointing in the rock walls is determined by field observations and logging in bore holes, and the results confirm the theory.
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| 13. |
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| 14. |
- Stephansson, Ove
(författare)
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Seismo-tectonics in Fennoscandia
- 1978
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Ingår i: Geologiska föreningens i Stockholm förhandlingar. - : Informa UK Limited. - 0016-786X. ; 100:3, s. 239-245
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Tidskriftsartikel (refereegranskat)abstract
- Studies of seismic risk in Sweden indicate that there is coherence between the epicentres of earthquakes and the tectonics. On the basis of the existing seismic data and the tectonics, eleven seismo-tectonic zones are suggested for the Fennoscandian Shield. The correlation between the gravity data, the late glacial movements and the seismo-tectonic zones is found to be positive
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Stephansson, Ove, et al.
(författare)
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The relationship between deformation and mineral composition in some fold structures
- 1977
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 99:2, s. 198-207
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Tidskriftsartikel (refereegranskat)abstract
- An attempt is made to correlate the chemical compositions of certain minerals from different parts of fold structures with the theoretical stress pattern. A partial analysis was made on amphibole, plagioclase, garnet, diopside, sphalerite and biotite with a microprobe and the theoretical stress pattern was calculated by means of the finite-element method (FEM). Two of the four fold structures investigated show a systematic variation in the chemistry of some minerals, but there is no simple relationship to the theoretical stress model. The Fe-Mg silicates from the hinge zones often show lower values of iron, compared with the rest of the structure. A systematic variation between co-existing minerals indicates that chemical equilibrium has been attained. In many cases, the studied minerals from a folded layer are quite constant, which may be due either to small pressure gradients or to the fact that we have chosen minerals and elements which are not very sensitive to pressure. Though stress-induced diffusion may create some chemical variations, small fluctuations in partial pressures and local chemistry will very soon mask this pattern.
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| 19. |
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