Annual report for Tanami JV from 14 October 1996 to 13 October 1997

Abstract

The Tanami mine is a 60:40 joint venture between Otter Gold NL and Acacia Resources Ltd with Otter Gold as managers. Gold was first discovered in 1900 and since 1990 in excess of a million ounces has been produced from 30 pits. The eighteen mining leases comprising the joint venture cover 88.84sq km and production for the reporting period was derived from eleven pits located within mining lease MLS167, the area of which is 38sq km. The mill has a capacity of 1.45 million tonnes per year and proven and probable reserves as at 30th June 1997 were 5,108,000 tonnes at 3.2g-t Au for 521,498 ounces and measured, indicated and inferred mineral resources are currently 8,357,000t at 2.92g-t Au for 783,998 ounces. A total of 133,800oz of gold were produced from 1,350,000t at an average grade of 3.08g-t Au. A total of 7.2 million bank cubic metres of waste were mined for a strip ratio of 13.4 : 1. A total of 33,500m of grade control RC drilling, 29,500m of exploration and development RC drilling, 4,302m of diamond drilling and 398,000 of percussion drill and blast metres were completed. A total of 199,000 samples were taken from grade control, exploration and development activities located on 34 prospects and analysed at the on site laboratory. The mining leases are located within a 30km long corridor of weakly metamorphosed, broadly folded Mt Charles beds that consist of intrusive and extrusive basalt and fine to coarse grained turbiditic siltstone to sandstone and carbonaceous sediments that are broadly folded between the Frankenia and Coomarie granite plutons. These structural features lie immediately north of the Trans-Tanami Lineament. Mineralisation within the Tanami mine corridor is orientated along 350 degrees, 020 degrees and 060 degrees trending structural elements that reflect strike-slip displacement associated with brittle deformation. The unique feature of this mineralisation is that is dips at a high angle to the bedding and as a consequence most drilling is orientated down dip of the bedding. Strong haematitic and silicic alteration is associated with the mineralisation and minor pyrite, arsenopyrite and chalcopyrite occurs with the mineralisation. Mineralisation is thought to be derived from either 300 degrees centigrade, magmatic hydrothermal or contact metamorphic fluids sourced from the thermal aureole of the Frankenia Granite. During the period exploration was undertaken on 34 prospects within the mining leases and RAB, RC and diamond drilling have returned numerous significant intersections that require follow-up. Diamond drilling below existing pits has intersected down plunge extensions of known mineralisation. Significant exploration potential exists within the mining leases as numerous geological, geochemical, geophysical anomalies and RAB, RC and diamond drilling intersections remain to be followed up.