Water–rock interactions : an investigation of the relationships between mineralogy and groundwater composition and flow in a subtropical basalt aquifer
Locsey, Katrina L., Grigorescu, Micaela, & Cox, Malcolm (2012) Water–rock interactions : an investigation of the relationships between mineralogy and groundwater composition and flow in a subtropical basalt aquifer. Aquatic Geochemistry, 18(1), pp. 45-75.
A holistic study of the composition of the basalt groundwaters of the Atherton Tablelands region in Queensland, Australia was undertaken to elucidate possible mechanisms for the evolution of these very low salinity, silica- and bicarbonate-rich groundwaters. It is proposed that aluminosilicate mineral weathering is the major contributing process to the overall composition of the basalt groundwaters. The groundwaters approach equilibrium with respect to the primary minerals with increasing pH and are mostly in equilibrium with the major secondary minerals (kaolinite and smectite), and other secondary phases such as goethite, hematite, and gibbsite, which are common accessory minerals in the Atherton basalts. The mineralogy of the basalt rocks, which has been examined using X-ray diffraction and whole rock geochemistry methods, supports the proposed model for the hydrogeochemical evolution of these groundwaters: precipitation + CO 2 (atmospheric + soil) + pyroxene + feldspars + olivine yields H 4SiO 4, HCO 3 -, Mg 2+, Na +, Ca 2+ + kaolinite and smectite clays + amorphous or crystalline silica + accessory minerals (hematite, goethite, gibbsite, carbonates, zeolites, and pyrite). The variations in the mineralogical content of these basalts also provide insights into the controls on groundwater storage and movement in this aquifer system. The fresh and weathered vesicular basalts are considered to be important in terms of zones of groundwater occurrence, while the fractures in the massive basalt are important pathways for groundwater movement.
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|Item Type:||Journal Article|
|Keywords:||Aluminosilicate mineral weathering, Basalt aquifer, Mass balance|
|Subjects:||Australian and New Zealand Standard Research Classification > BIOLOGICAL SCIENCES (060000)|
|Divisions:||Current > Schools > School of Earth, Environmental & Biological Sciences
Current > QUT Faculties and Divisions > Science & Engineering Faculty
|Deposited On:||03 Jul 2012 23:59|
|Last Modified:||03 Jul 2012 23:59|
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