Thesis: The geochemistry, distribution and formation mechanisms of calcretes in the semi-arid Hamersley Basin of northwest Australia
Calcretes are terrestrial accumulations of carbonates, which form a major component in near-surface geology. Calcretes are widespread in the semi-arid Hamersley Basin of the Pilbara region of northwest Australia, an area also renowned for its high quality iron ore. Carbonate minerals precipitate from groundwater within the phreatic and vadose zone. However, it is not known what processes and conditions have occurred for these accumulations of calcrete to have formed and whether lateral groundwater flow or soil forming processes have influenced their distribution. My research seeks to establish the distribution, formation mechanisms and evolution of calcrete deposits in the Hamersley Basin. Characterisation of calcrete at both local and regional scales will provide information for planning and management of water resources in the Hamersley Basin.
Why my research is important
Calcretes in the Hamersley Basin have hydrogeological significance as they influence the flow and recharge of aquifers. This is particularly important in the Pilbara as local hydrology is currently being altered due to water abstraction, as well as dewatering and discharge associated with mining practices. In some locations calcretes form an impermeable layer between deep saline and shallow fresh groundwater. Dissolution of calcrete may result in mixing of deep and shallow groundwater, resulting in increased salinity near the surface. These calcretes also impede evaporation from the deeper aquifer, which in turn influences the distribution of local water resources and groundwater dependent ecosystems. My research will provide the first detailed characterisation of calcretes in the Pilbara and thus will increase understanding of how existing calcretes and those currently forming may be impacted by ongoing water abstraction and dewatering by mining activities.