Bynoe Joint Venture Annual Report EL 5096

Abstract

This report is submitted to the Northern Territory Department of Mines and Energy and details exploration carried out on EL 5096 during the period April 1988 - April 1989. Exploration Licence 5096 is located on the Cox Peninsula south west of Darwin. It is one of a number of licences held by the Bynoe Joint Venture in the region, for the exploration and development of cassiterite and tantalite pegmatite and alluvial deposits. The Bynoe Joint Venture partners are Greenbushes Ltd and Barbara Mining Corporation a subsidiary of Bayer A.G. of West Germany. Greenex the exploration division of Greenbushes Ltd is the operator of the joint venture. Samples of weathered pegmatite were collected from backhoe trenches or auger drill holes. Samples were collected at approx. 1.5 m intervals from the trenches and holes and stored in plastic bags. Aluminium tags stapled to the bags designated the sample numbers. The trenches were channel sampled and logged. Approximately 10 litres of sample was collected from each interval. Care was taken in digging and the sampling of the trenches to get below the enriched eluvial zone. All samples were hauled to a central processing facility by the main camp site. Between 6 litres and 10 litres of sample was collected from each trench sample. A 6 litre volume of loosely compacted sample was measured in volume cylinders. The sample was mechanically mixed with calgon and water in a steel bucket. In this process the clay was dispersed and formed a slurry. Water was slowly injected into the sample bucket forcing the suspended clay to be decanted. Care was taken to avoid the overflow of 'fine heavies' . The de-slimed sample was fed through a trommel with 10 mm screen onto a 1.75 m diameter concentrating cone, the slope of the cone and the water velocity flowing against the slope caused the heavy minerals : cassiterite, tantalite, illmenite, magnetite, rutile, zircon etc. : to be separated from the light fraction, which was predominantly quartz and muscovite. Like any form of gravity concentration the recovery of heavy minerals will be dependent of their grainsize relative to that of the gangue minerals. The plus 10 mm trommel oversize was rejected. At Leviathan the oversize appears to contain little 'locked' cassiterite and tantalite. No account has been taken of mineralised oversize in the evaluation of the Projects Mineralised Reserves. Any cassiterite or tantalite derived from oversize will be additional to that predicted by the projects reserve grade. At the Greenbushes Mine Laboratory the entire concentrate sample was pulverized for 2 minutes in a 200 ml chrome steel bowl on a vibrating pulverizer. The pulverized sample was fused with lithium borate containing lanthanum oxide to make a suitable glass disc for X-ray spectrographic analysis. The following elements, Nb205, Sn02 and Ta205 were determined on the disc. Sampling System Checks - A number of programmes were in operation to monitor the procedures adopted in concentrating and analysing exploration samples. Analysis was continuously re-checked by the Greenbushes Ltd Laboratory.