A correlation between the evolution of mineralizing fluids and the geomechanical development of a shear zone as illustrated by the Henderson 2 Mine, Quebec

Univ. Que. a Chicoutimi, Sci. Terre, Chicoutimi, PQ, Canada

Two ore zones, one enclosed within a shear zone (zone B) and the other in a subsidiary structure (zone D). At onset of the shear zone, subsidiary fracture patterns are developed in second order faults in the following sequence. At peak strength Riedel shears are formed which propagate out into the walls of the shear zones producing the zone D structure. After peak strength, restraint (P) shears are developed in the thrust attitude within the shear zone. Principal displacement shears, (D) developed toward residual strength in the direction of movement. The continuation of the shear displacement gives rise to schistosities within the main shear zone. While the main shear zone and the P and D shears within the main shear zone were in continual movement, the subsidiary zone D structure, once formed retained a simple fracture pattern and moved little in comparison to the main shear zone. Mineralizing fluids introduced into this shear environment show a similar pattern of evolution, with a wider range of homogenization and halite disappearance temperatures in the more active zone B than within zone D. Systematic variations of Ca/Na and Ca/Mg indicate migration. --Modified journal abstract.

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