geophysics
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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. These line dataset from the Murrindal, Vic, 1996 VIMP Survey (GSV3060) survey were acquired in 1995 by the VIC Government, and consisted of 15589 line-kilometres of data at 200m line spacing and 80m terrain clearance. To constrain long wavelengths in the data, an independent data set, the Australia-wide Airborne Geophysical Survey (AWAGS) airborne magnetic data, was used to control the base levels of the survey data. This survey data is essentially levelled to AWAGS.
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This web service delivers metadata for onshore active and passive seismic surveys conducted across the Australian continent by Geoscience Australia and its collaborative partners. For active seismic this metadata includes survey header data, line location and positional information, and the energy source type and parameters used to acquire the seismic line data. For passive seismic this metadata includes information about station name and location, start and end dates, operators and instruments. The metadata are maintained in Geoscience Australia's onshore active seismic and passive seismic database, which is being added to as new surveys are undertaken. Links to datasets, reports and other publications for the seismic surveys are provided in the metadata.
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As part of initiatives by the Australian and Queensland Governments to support energy security and mineral exploration, a deep seismic reflection survey was conducted in 2007 to establish the architecture and geodynamic framework of north Queensland. With additional support from AuScope, nearly 1400 km of seismic data were acquired along four lines, extending from near Cloncurry in the west to almost the Queensland coast. Important results based on the interpretation of the deep seismic data include: (1) A major, west-dipping, Paleo-proterozoic (or older) crustal boundary, which we interpret as a suture, separates relatively homogenous, thick crust of the Mt Isa Province from thinner, two layered crust to the east. This boundary is also imaged by magnetotelluric data and 3D inversion of aeromagnetic and gravity data. (2) East of the Mt Isa Province the lower crust is highly reflective and has been subdivided into three mappable seismic provinces (Numil, Abingdon and Agwamin) which are not exposed at the surface. Nd model ages from granites sampled at the surface above the western Numil and central Abingdon Seismic Provinces have very similar Nd model ages, suggesting that both provinces may have had a very similar geological history. By contrast, granites sampled above the eastern Agwamin Seismic Province have much younger Nd model ages, implying a significantly younger component in the lower crust; we consider that the Agwamin Seismic Province contains a strong Grenvillean-age component.
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Legacy product - no abstract available