Investigating the relationship between the dimension of the Riedel fault blocks and amount of open spaces in brittle shear zones: analogue and numerical modeling

The geometry of mineral deposits in brittle shear zones depends on the open spaces in these zones and especially in the Riedel structures. The systematic intersection of Riedel fractures in the path of these zones causes the formation of Riedel blocks, the dimensions of which are proportional to the spacing between these fractures. By increasing the shear strain (γ) in a shear zone and consequently the rotation of these blocks, it is expected to create proportionate open spaces that with the penetration and deposition of ores in these spaces, causes the formation of mineral veins in all these spaces. Since the amount of open spaces in shear zones is different, in this study, through analogue and numerical modeling using 3DEC software, it was shown that the change in the dimensions of the blocks in equal kinetic conditions is one of the parameters affecting the amount of open spaces of these zones. Therefore, this volume of open spaces in a single range of different shear zones, which are different from each other in terms of spacing of Riedel fractures, is inversely related to increasing the dimensions of Riedel blocks; the more Riedel blocks, the more block rotation and consequently more space is expected. As the shear strain increases during a progressive deformation, in bigger dimensions of the Riedel blocks tested, more force is expended on inter-block slips than on block rotation and open space. The amount of open spaces created in numerical modeling shows good agreement with this type of modeling.