Geostatistical analysis of fractures in shear zones in the Chibougamau area: applications to structural geology

Abstract

A geostatistical approach is used to analyze the spatial distribution of fracture density in shear zones. The methodology proposed is illustrated with data obtained from the mapping of drift walls at the Henderson mine in the Chibougamau mining district, Québec. Fracture sets are defined using statistical characterization of fracture orientation and genetic parameters of fractures. Fracture density is defined as a function of the frequency, length and width of fracture traces measured on rock exposures. The spatial distribution of each set is estimated using three variables based on structural interpretation of fracture density ranges: the absence of fracture, the presence of clusters of small fractures with negligible thickness and the presence of fractures with measurable thickness. Results are presented in the form of variograms and of kriged contour maps. A positive relationship is shown between the range of the variogram and the type of fracture development. Furthermore, indicator maps provide insight into the spatial relationship between the major and the minor fractures in the investigated shear zone.