Victoria River Downs Gravity Survey

Abstract

A helicopter-supported gravity survey, consisting of 1,589 gravity readings, has been completed in two areas on granted Victoria River Downs tenure. The survey was cofunded by the Northern Territory Government under the government's Geophysics and Drilling Collaboration Program ('GDCP'). The northern part of the survey (based on readings spaced 1 km x 1 km) was designed to target a major north south fault and associated splay faults and domes over a strike length of 50 km. This area contains extensive stream sediment geochemistry zinc-lead anomalies. Preliminary examination of the data indicates a broad gravity high was located 30 km south of the Victoria Downs Homestead, flanked by lower frequency gravity anomalies. Of particular interest are anomalies located adjacent to the major north south fault. Gravity anomalies adjacent to an interpreted feeder structure represent very localized areas of rocks denser than the surrounding sedimentary rocks. These denser rocks could be buried sulphides and may represent future drill targets. The southern half of the survey in the Mt Sanford area (100 km south west of Victoria River Downs Homestead) was also conducted initially on a 1 km x 1 km basis and then infilled to 500m x 500m. Preliminary examination of the data shows a broad gravity low corresponding to a major north west trending fault, flanked to the south by linear gravity anomalies which have a strike lengths of over 3 km. One of the gravity anomalies is coincident with a magnetic anomaly. Field examination shows that outcrop, east of the gravity anomaly trend, adjacent to the fault consists of steeply dipping quartzite. There is little outcrop in the vicinity of the gravity anomalies where stratigraphy is sub horizontal. The gravity anomalies adjacent to the fault could be targets under our current exploration model. Modelling and interpretation of the data, from both areas, is currently being undertaken by Southern Geoscience.