Targeting Fractured Rock Aquifers using Magnetic Data
- 1. Southern Geoscience Consultants, Heather.Ballantyne@sgc.com.au
- 2. Southern Geoscience Consultants, Karen.Gilgallon@sgc.com.au
- 3. Southern Geoscience Consultants, Sharon.Lowe@sgc.com.au
Description
Fractured Rock Aquifers are an important source of water with approximately 40% of groundwater in Australia present in fractured rock. The water extracted from fractured rock aquifers is utilised in mining, irrigation, town water supply and stock watering. A third of water extraction bores in Australia are in fractured rock systems. Understanding the possible size, potential for fracturing and accurate locations for targeting bores is an important part of exploring for fractured rock aquifers. Magnetic data, both airborne and ground, can be used to assist in mapping fractures, dykes and identifying rock types with favourable rheology for hosting fractured rock aquifers. Magnetic data have been collected by both government geological agencies and mining and exploration companies across large parts of Australia, ranging from 400m spaced data down to very detailed 25m spaced surveys. This is a low-cost solution for targeting bores as data can be acquired free of charge from government surveys or open file searches. The data can be filtered in several ways, such as second vertical derivative, to highlight the location of faults, fractures and potential water traps along dykes and other potential aquatards. Two case studies are presented showing the use of magnetic data in identifying locations for potential fractured rock aquifers. The first example is a 25m spaced survey from the Pilbara where water was required for a processing plant for a mining company. The interpretation was completed in collaboration with the company and hydrologists to identify the best potential sites for drilling a water bore. Another example from the Great Southern, Western Australian used 80m line spaced magnetic data, which was interpreted to identify priority drilling targets close to existing infrastructure. For fractured rock aquifer exploration, magnetic data filtering and interpretation is a cost-effective solution for identifying targets for exploration by drilling.
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