1998 Volume 9 Issue 4 Pages 221-226
Crustal shear zones are believed to have formed at deeper levels under high ductile, high PT, conditions. Subsequent rise of the shear zone rocks up to the surface, involves a series of deformational and metamorphic processes which leave their effects/imprints in the form of new structures, textures, fabric, and the related petrographic, mineralogical and geochemical features, all of which can be observed and measured. All these elements can be restructured or reorganized to develop quantitative models.
Depending upon the type of available data, only one or some specific models for a shear zone can be developed. Amathematical modelcan be developed when the measurable variables (or the controlling factors) of a shear zone can be approximated by some limited range. A mathematical model can be made more realistic if some random components of the shear zone (or the system) - e.g. vertical uplift, rise or fall of temperature, etc-can be considered. This gives rise to astochastic modelfor a shear zone. If the present-day tectonic set-up of a shear zone can be considered in terms of the sum total of a few structural processes (as outlined in the paper) together with one or two random components (outlined in the paper) operative in the system, astochastic processmodel can be developed for the shear zone. Aprocess-response model can be developed when the structural/tectonic factors that constitute the “causes” - i.e. process elements - and those constituting the “effects” - i.e. response elements - for a shear zone are known. A shear zone may take up alinear modelwhen all the associated structural data that have given rise to the development of the shear zone are directly observable and measurable in field sections, such that the observational data yield a certain linear relation of the type y=a+bx.
The method of developing a quantitative model for a shear zone has been demonstrated in the paper by taking the actual situation of a shear zone.
