3-D stochastic modeling and simulation of fault zones in the Albalل granitic pluton, SW Iberian Variscan Massif

A distribution of fracture index (FI) is obtained from stochastic modeling and simulation to characterize quantitatively the fault system of the Mina Ratones area in three-dimensions (3-D). FI is a quantitative estimate of the fracture intensity in discrete domains of the granitic rock massif. The resulting 3-D grids, expressed as block (cells) models or contoured isosurfaces of FI, show high and low FI zones. The correlation of these zones with mapped faults allows two structural domains to be distinguished: (1) variably irregular surfaces of high FI, and (2) rhomboidal blocks of low FI located inside them. High FI domains (FI>4.2 m−1) are interpreted as fault zones, since there is a good correlation at the surface between the domains and traces of the major fault zones. Low FI blocks (FI<2.5 m−1) correspond to less fractured granite. The contact between high and low FI domains is gradual. The high and low FI structural domains may correspond with the damage zone/fault core and the protolith in the model for fault zone architecture of Caine et al. (1996). Therefore, 3-D grids of the FI in granitic areas affected by strike-slip brittle tectonics, such as Mina Ratones, constitute an image of fault zone architecture.