Application of Open System Modelling to Studies of Secondary Mineralization (Koongarra) and Rock Matrix Diffusion (Kräkemäla)

Summary

The open system modelling technique was developed to interpret the results of the natural analogue study being conducted in the Alligator Rivers region of the Northern Territory of Australia. The model was prepared in a general form, and then compared with other open system models. A modified version of the model was used to study the movement of uranium in the secondary mineralization deposit at Koongarra. The results were consistent with a general understanding of a roll front effect. The average overall uranium mobility rate had leaching characteristics near the original ore deposits which systematically changed to a deposition mechanism farther from the primary body. The derived timescale for the event was in agreement with the results of other modelling attempts. A second modified version of the open system model allowed uranium mobility in the region of a water conducting fracture in crystalline rock to be modelled. Experimental data by Smellie, MacKenzie and Scott from a Kräkemäla granite sample containing a fracture were used to test the model. The calculated uranium mobility rate supported the assumption that the radionuclides can disperse into the rock matrix through a diffusion mechanism.