palaeomagnetism
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Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This magnetic grid has a cell size of 0.001 degrees (approximately 106m).The data are in nanoTesla (or nT). The data used to produce this grid was acquired in 2004 by the QLD Government, and consisted of 74554 line-kilometres of data at 400m line spacing and 80m terrain clearance. The data has had a variable reduction to the pole applied to centre the magnetic anomaly over the magnetised body. The VRTP processing followed a differential reduction to pole calculation up to 5th order polynomial. Magnetic inclination and declination were derived from the IGRF-11 geomagnetic reference model using a data representative date and elevation representative of the survey.
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Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This GSWA P1177 Katanning TMI grid geodetic has a cell size of 0.00083 degrees (approximately 85m). The units are in nanoTesla (or nT). The data used to produce this grid was acquired in 2008 by the WA Government, and consisted of 75805 line-kilometres of data at a line spacing between 100m and 400m, and 60m terrain clearance.
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Interpretation of magnetic field data is complicated by the presence of remanent magnetization and benefits from palaeomagnetic and rock magnetic studies. Additionally, the planning of palaeomagnetic sampling sites and mapping of the distribution of magnetizations recovered in palaeomagnetic studies benefits from inspection of magnetic field imagery. These inter-relationships between magnetic field interpretation and palaeomagnetic studies are particularly important in Australia, where deep weathering and extensive cover by younger formations commonly lead to the magnetic field data being the most complete and detailed source of information for basement-related geological mapping and mineral exploration, and where there are few opportunities for direct palaeomagnetic sampling. For the assistance of both magnetic field interpreters and palaeomagnetists, we have developed a database tool to document and interrogate this relationship. We have started to populate the database, and are planning the facilities required to make the database available as an interactive, web-based resource. The key objectives are to facilitate interpretation of magnetic field data, increase reliability in developing deep drilling targets from magnetic field interpretation, and to better establish the spatial range of magnetizations related to igneous, metamorphic, thermal, alteration and mineralization events. Our intention is to establish a widely used, interactive, minimally-moderated resource rather than a more definitive but possibly less useful one. We envisage that the data base will grow primarily through public contributions, and will also be the forum for debate and speculation regarding Australian magnetization events. We believe that this model is appropriate for wider, global application.
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Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This magnetic grid has a cell size of 0.00082 degrees (approximately 84m).The data are in nanoTesla (or nT). The data used to produce this grid was acquired in 2005 by the NSW Government, and consisted of 18763 line-kilometres of data at 400m line spacing and 60m terrain clearance. The data has had a variable reduction to the pole applied to centre the magnetic anomaly over the magnetised body. The VRTP processing followed a differential reduction to pole calculation up to 5th order polynomial. Magnetic inclination and declination were derived from the IGRF-11 geomagnetic reference model using a data representative date and elevation representative of the survey.
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Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This GSNSW Murray Basin magnetic grid geodetic has a cell size of 0.00078 degrees (approximately 80m). The units are in nanoTesla (or nT). The data used to produce this grid was acquired in 2005 by the NSW Government, and consisted of 95495 line-kilometres of data at 400m line spacing and 60m terrain clearance.
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Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This GSQ Mt Isa Southeast magnetic grid geodetic has a cell size of 0.00083 degrees (approximately 88m). The units are in nanoTesla (or nT). The data used to produce this grid was acquired in 2006 by the QLD Government, and consisted of 100960 line-kilometres of data at 400m line spacing and 80m terrain clearance.
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Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This GSQ Mt Isa Southwest magnetic grid geodetic has a cell size of 0.00083 degrees (approximately 88m). The units are in nanoTesla (or nT). The data used to produce this grid was acquired in 2006 by the QLD Government, and consisted of 139836 line-kilometres of data at 400m line spacing and 80m terrain clearance.
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Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This GSWA Ashburton magnetic grid geodetic has a cell size of 0.00083 degrees (approximately 89m). The units are in nanoTesla (or nT). The data used to produce this grid was acquired in 2006 by the WA Government, and consisted of 106235 line-kilometres of data at 400m line spacing and 60m terrain clearance.
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Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This GSWA Musgrave Extensions magnetic grid geodetic has a cell size of 0.00083 degrees (approximately 88m). The units are in nanoTesla (or nT). The data used to produce this grid was acquired in 2006 by the WA Government, and consisted of 83777 line-kilometres of data at 400m line spacing and 60m terrain clearance.
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Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This GSWA Devils Creek Magnetic Grid Geodetic has a cell size of 0.00083 degrees (approximately 84m). The units are in nanoTesla (or nT). The data used to produce this grid was acquired in 1999 by the WA Government, and consisted of 3935 line-kilometres of data at 300m line spacing and 70m terrain clearance.