HR: 1630h
AN: NS34A-03    [Abstracts]
TI: Airborne Gravity Gradiometry Resolves a Full Range of Gravity Frequencies
AU: * Mataragio, J
AF: Bell Geospace Inc, 2 Northpoint Drive suite 250, Houston, TX 77060, United States
AU: Brewster, J
AF: Bell Geospace Inc, 2 Northpoint Drive suite 250, Houston, TX 77060, United States
AU: Mims, J
AF: Bell Geospace Inc, 2 Northpoint Drive suite 250, Houston, TX 77060, United States
AB: Abstract Airborne Full Tensor Gradiometry (Air\-FTG^R) was flown at high altitude coincident with Airborne Gravity (AG) flown in 2003 in West Arnhem Land, Australia. A preliminary analysis of two data sets indicates that the Air\-FTG^R system has the capability of resolving intermediate to long wavelengths features that may be associated with relatively deeper geological structures. A comparison of frequency filtered slices and power spectral density (PSD) for both data sets using the short (> 5 km), intermediate (10 km) and long (20 km) wavelengths reveals that high altitude Air\-FTG^R data show greater response in high frequency anomalies than a conventional Airborne Gravity and matches well with the AG even at the longest wavelengths anomalies. The effect of line spacing and target resolution was examined between the two data sets. Reprocessed gradient and AG data at 2, 4 and 6 km line spacing suggest that Air\-FTG^R could be effectively flown at a comparatively wider line spacing to resolve similar targets the AG would resolve with tighter line spacing. Introduction Airborne Full Tensor Gradiometry (Air\-FTG^R) data have been available to the mining industry since 2002 and their use for geologic applications is well established. However, Air\-FTG^R data has been mostly considered and used in mapping and delineation of near surface geological targets. This is due to the fact that gravity gradiometer measurements are well suited to capture the high frequency signal associated with near\-surface targets ( Li, 2001). This is possible because the gradiometer signal strength falls off with the cube of the distance to the target. Nonetheless, in recent years there has been an increasing demand from the mining, oil, and gas industry in utilizing Full Tensor Gravity Gradiometer as a mapping tool for both regional and prospect level surveys. Air\-FTG^R as a Regional Mapping Tool Several, relatively low altitude surveys have been successfully flown in Brazil, Canada and Australia mostly targeting large, regional\- scale crustal structures as well as regional mapping of both lithology and regolith. Air\-FTG^R mapping is especially effective in areas of thick lateritic and/or clay cover where other geophysical methods such as airborne magnetics or electromagnetics become less effective. For instance, an Air\-FTG^R survey was successfully flown in Brazil in the Province of Minas Gerais, where several crustal\-scale structures associated with iron oxide mineralization were identified ( Mataragio et. al., 2006). In addition, in 2006 Air\-FTG^R had good success in the regional mapping of structures associated with Iron Oxide Copper Gold (IOCG) and uranium mineralization in the Wernecke Mountains in the Yukon, and Northwest Territories, Canada. On the basis of these successful surveys, Bell Geospace has initiated a number of high altitude test surveys aiming at evaluating the performance of the Air\-FTG^R system in capturing low frequency signal that may be associated with regional\-scale, deeper structures. One of the test surveys was conducted in December of 2006 in Australia, where the performance of Air\-FTG^R and the conventional Airborne Gravity were evaluated. Airborne gravity is currently considered well suited for capturing low frequency signal.
UR: http://www.bellgeo.com
DE: 0900 EXPLORATION GEOPHYSICS
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting