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

Abstract

In April 2000 BHP conducted six FALCON airborne gravity gradiometer (AGG) test surveys over the Cannington Ag-Pb-Zn ore body in NW Queensland, Australia. The purpose of the test surveys was to demonstrate the capabilities of the AGG instrument by comparison with known detailed ground gravity data, to investigate the effects of source distance on signal strength by flying surveys at various altitudes, and to estimate AGG instrument noise levels in survey conditions. The processed FALCON gD data compare very favorably with the upward-continued residual ground gravity data, capturing most geological features and clearly delineating the Cannington ore body. Analysis of the effects of source distance on signal strength indicates that with a nominal flying height of 120m, the FALCON AGG instrument can detect the gravity anomaly from a deposit with the size and geometry of Cannington through 130m overburden. By repeating a survey using the same acquisition parameters we can make an estimate of the RMS noise of the instrument under survey conditions. Analysis of repeat survey readings show that the FALCON AGG instrument attained a noise level of 10 Eötvös RMS in the bandwidth from 0.0 Hz to 0.125 Hz during the Cannington test flights.