Falcon airborne gravity gradiometer survey results over the Cannington Ag-Pb-Zn deposit

Christensen, Asbjørn Nørlund; Mahanta, Asmita M.; Boggs, D.B.; Dransfield, Mark

doi:10.1071/aseg2001ab019

Cited by 13 publications

(10 citation statements)

References 1 publication

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“…Th e vertical slices of Figure 11 re prese nt the results of the gzz component inversion, and the extent of the anomalous body is mor e sharply defined . The presence of the orebod y on the southern side of the fault shows up at a greate r depth, as is expected from the local geology (Christensen et a!., 2001). The other geological features mentioned while describing the im ages for g, are all shown here.…”

Section: Agg Survey and Data Interpretationsupporting

confidence: 63%

Three‐dimensional regularized focusing inversion of gravity gradient tensor component data

Еllis²,

2004

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We develop a new method for interpretation of tensor gravity field component data, based on regularized focusing inversion. The focusing inversion makes its possible to reconstruct a sharper image of the geological target than conventional maximum smoothness inversion. This new technique can be efficiently applied for the interpretation of gravity gradiometer data, which are sensitive to local density anomalies. The numerical modeling and inversion results show that the resolution of the gravity method can be improved significantly if we use tensor gravity data for interpretation. We also apply our method for inversion of the gradient gravity data collected by BHP Billiton over the Cannington Ag‐Pb‐Zn orebody in Queensland, Australia. The comparison with the drilling results demonstrates a remarkable correlation between the density anomaly reconstructed by the gravity gradient data and the true structure of the orebody. This result indicates that the emerging new geophysical technology of the airborne gravity gradient observations can improve significantly the practical effectiveness of the gravity method in mineral exploration.

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Section: Agg Survey and Data Interpretationsupporting

confidence: 63%

Three‐dimensional regularized focusing inversion of gravity gradient tensor component data

Еllis²,

2004

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“…The modelled GGI output in response to the inertial sensitivities is subtracted from the observed output. Application of this technique to the output of the GGI, when it is adequately compensated by its internal mechanisms, results in the performance levels reported elsewhere Mahanta et al, 2001;Liu et al, 2001;Christensen et al, 2001) .…”

Section: Post-processing Compensationmentioning

confidence: 77%

“…A further program of test, modification, and development ensued before they were deployed in routine survey operations in 1999 and 2000. These instruments have proved suitable for use in mineral exploration with sufficient sensitivity and resolution for detection of the small localised gravity anomalies associated with mineral deposits and for regional mapping Mahanta et al, 2001;Christensen et al, 2001). The most effective demonstration of this capability is perhaps the detection of the gravity anomalies associated with Kimberlite pipes of~100 m diameter, and in resolving dykes separated by 300 m .…”

Section: Introductionmentioning

confidence: 99%

Falcon Gravity Gradiometer Technology

Lee

2001

Exploration Geophysics

110

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BHP Billiton's FALCON airborne gravity gradiometer is a derivative of the Gravity Gradient Instrument (GGI) developed by Bell Aerospace (now Lockheed Martin) between 1975 and 1990. The basis of the GGI design is an accelerometer complement consisting of four accelerometers equi-spaced on a circle with their sensitive axes tangential to the circle. This configuration rejects both common mode acceleration and rotations about the axis perpendicular to the plane of the complement. The complement remains intrinsically sensitive to rotation rates about axes in the plane of the complement and is sensitive to the acceleration environment to the extent that there is imbalance in the accelerometer sensitivities. Rotation of the complement about the perpendicular axis moves the gradient signal to twice the rotation frequency, away from the effects of low frequency accelerometer bias changes. The GGI is mounted in a high-performance inertial stabilised platform to reduce rotation of the instrument so that its sensitivity to this motion does not represent a significant noise source.The GGI accelerometers are designed for very low noise, requiring hard evacuation, high pendulosity, low spring constant and attention to the constrainment loop. Accelerometer pairs are aligned with precision and their sensitivities and frequency responses are matched. The scale factor (sensitivity) and alignment of the sensitive axis of each accelerometer are adjusted by compensation feedback loops to minimise accelerometer imbalance by monitoring the response of the system to specific stimuli.The requirements of survey operations were taken into account during development of the system and the result is an instrument which requires limited preparation, is largely automated during surveys, places few restrictions on flight planning and has been operated in harsh ambient conditions. Data processing is streamlined and data quality can be checked immediately after a flight.

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“…. In 2000, the first work with the Falcon airborne gravity gradiometer system was carried out over Cannington (Christensen et al 2001). Also in 1993, a seismo-electric trial was carried out (A. Kepic per com 2014).…”

Section: Geophysical Surveysmentioning

confidence: 99%

“…In Fig. 8, images of the Falcon gD (Christensen et al 2001) and Geotem 25 Hz dB/dt Z Ch 11-6.3 msec (BHP 1995). The Falcon survey shows the strong gravity high associated with the Cannington Northern zone, which merges with a much larger feature to the north and northeast.…”

Section: Airborne Surveysmentioning

confidence: 99%