Remote sensing for resources development and environmental management: Remote sensing for resources development and environmental management

damen, m. c. j.

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Multivolume work

Persistent identifier:: 856342815

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856342815

Language:: English

Additional Notes:: Volume 1-3 erschienen von 1986-1988

Editor:: Damen, M. C. J.

Document type:: Multivolume work

Volume

Persistent identifier:: 856641294

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Scope:: IX Seiten, Seiten 551-956

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A,. A. Balkema

Identifier (digital):: 856641294

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(26,7,2)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: Damen, M. C. J.

Editor:: International Society for Photogrammetry and Remote Sensing, Commission of Photographic and Remote Sensing Data

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: 5 Non-renewable resources: Geology, geomorphology and engineering projects. Chairman: J. V. Taranik, Liaison: B. N. Koopmans

Write comment:: Wegen zu enger Bindung kommt es teilweise im Original zu Textverlust.

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: Application of remote sensing in the field of experimental tectonics. J. Dehandschutter

Document type:: Multivolume work

Structure type:: Chapter

592 E«»t«fn coopM Wfeatern coup*« 5C 5D Figure 5c. Schematical localisation of geochemical anomalies (black squares) at the intersection of brec- ciated lineaments defining closures of synforms. Figure 5d. Stereographic projection of minor fold axes in the emerald bearing Eastern Cordillera, Colombia. 2.3.Economic aspects The deviatoric part of the horizontal stress field seems to split the crust in the direction of maximum horizontal compression before it fails by shear faul ting. Fractures with this appropriate direction and relation to shear fractures appear filled up by epi genetic solutions of possible economic interest. If the Zambian quartz-dykes are examples of a non-minera- lized fill, kimberlite dykes and pipes outcropping un der the same favourable conditions with respect to strike and attitude in the Lofoi area (Shaba, Zaire), are more interesting targets. Geochemical exploration in the emerald bearing part of the Eastern Cordillera, Colombia, illustrates the effects of the stretching and thorough fracturing in the lowermost beds of the passively folded and faulted synforms. All anomalies indicating environments fa vourable for emerald mineralization are situated at the intersection of brecciated lineaments bordering some of the synforms (fig. 5c). 3 THE CONTINENTAL STRESS FIELD It is currently accepted that, except for uplifted and isostatically compensated regions where the stress field would be tensional (Artyushkov 1973), most of the continental plates are slightly compressional (i.g Fleitout & Froidevaux 1983). The lithosphere act as a guide for this deviatoric field and may be treated as a continuum. The repetitive pattern of trends of line aments and their spatial relationship with geological structures indeed suggest that the former are the effects of a uniform strain emanating from continuous and homogeneous processes. As far as the distribution of the stress field within the Earth's lithosphere and crust is concerned, the classical theory of a conti nuous elastic plate may be applied. Much of the obser ved strain in the crust however is of ductile nature and results from plastic processes. The applicability of elastic theory to geological processes in nature is thus restricted to the time period between the on set of loading of the planar continuum to the moment the elastic material fails by brittle fracturing or deforms in a plactic way. 3.1 The homogeneous field The stress field in the plate interior depends largely on the strength of the applied forces, on the geometric outline of the loaded plate and on the boundary condi tions. Pure shear does not rotate the strain axes and stress and strain remain co-axial. A study implemented on a triangular body (Dehandschutter in prep.) shows a good gross correlation of the obtained stress tra jectories and lines of elastic slip with the observed strain in the triangular corner of the South America Plate, the northern Andes. Nevertheless is it very clear as well that factors of lower order do control stress distribution and strength of the deviatoric field. The elements of the analysis given in 2 above suggest that a prime factor in control of the stress field and the resulting fi nite strain, is the presence of intersecting groups of lineaments which apparently act as discontinuities in the uniform crust. The elastic constants of the solid in the lineaments may either be higher or lower than the corresponding values in the plate's interior. 3.2 The discontinuous field In order to evaluate the influence weak discontinui ties may have on the stress field, a triangular plate made of photoelastic resin was cut in two perpendi cular directions (figs. 6,7) representing a possible combination of ENE and NNW lineaments. The lineaments or weak discontinuities in the model were filled with another resin the modulus of elasticity of which is 5 times less stiff than the material in the interior of the plate. The photoelastic analysis was seconded by a numeric finite elements control (fig. 7). Some results of the experiments done on the trian gle are extendable to more universal conditions. It is found that the primary or undeviated field which is known from the investigation of the homogeneous triangle obtains in the interior of the blocks se parated by weak discontinuities. The weak lineaments create a field of influence around their strike (fig. 6a) in which the expected trajectories (fig. 6a) of maximum compression (pri mary field) are deflected towards parallelism with the lineaments and the edges of the relatively stiff blocks (fig. 6c). The adges of the stiff blocks have the tendency to act as stress guides. The degree to which trajectories inside the blocks are deflected depends on the elastic contrast between the block and the weak lineament. Figure 6. Elastic stress distribution in a triangle cut by weak discontinuities. A. Fields of influence of weak zones and sigma 1-trajectories in homogeneous triangle; B. Azimuth and magnitude of axes of maximum and minimum compression, thickness in lineaments = thickness in blocks; C. Refracted and reflected tra jectories; D. Axes of max. and min. compression, thickness lineaments = thickness blocks/2. Trajectories entering or leaving the weak linea ments are strongly refracted (fig.6c). The axes of minimum compression are re-oriented inside the zones where they strike parallel to the trend of the line aments. The axes of maximum compression correspon dingly turn towards perpendicularity with the res pective lineaments. The angle of incidence of the Figure 7. A. Photoe! compressi< trajector: with respe the axis c trajectory side as we cross the Diminisl pared to t enhances t Finally stress whi tions of t four corne tinuities. within the tions of t 4 DISCUSSI Accepting related to crust whic tal solids rues of th though not spatial re logical st The devi higher tha latter, wi static. Sma11 in the blocks direction directions appear to direction block depe within the the loadin brittle te gonal posi

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