2013 Group Technical Report, GR159-10, MLN 2, MLN 3, MLN 951, MLN, 952, MLN 953, MLN 956, MLN 957, MLN 958, MLN 959, MLN 960, and MLN 961, 1 July 2012 to 30 June 2013

Abstract

Groote Eylandt is predominantly composed of a stable basement of Proterozoic quartz sandstones and quartzites. The overlying manganese deposits are part of a blanket of Cretaceous sediments lapping onto the western margin of the Proterozoic basement sandstones and quartzites of the McArthur Basin. The manganese orebody is a sedimentary layer, consisting of manganese strata occurring between clay and sand beds and gently undulates beneath the western plains of the island. It extends over an area of about 50 square kilometres as an almost continuous horizon ranging in thickness up to 11 metres. The ore body is thus essentially stratabound and strataform in character. A number of drilling campaigns were conducted during the reporting period. To increase the confidence in the resource and to convert resource into reserve, an RC resource definition drilling program was carried out. A total of 783 Reverse Circulation (RC) holes were drilled for 20,173m. Diamond drilling was carried out in order to update geometallurgical assumptions and to develop a short term mining model. A total of 173 diamond holes were drilled totalling 4,043m. Minor drilling and soil testing was also carried out for the installation of environmental ground watering bores, 11 holes were drilled totalling 87 metres. In addition, minor drilling was completed on selected existing and planned tailings dams for SPT testing and for the installation of piezometers, 14 holes were drilled for a total of 242m. As part of the East Arnhem Exploration Programme, 4 deep diamond core holes were drilled on the mining leases in order update current understanding of the stratigraphic and biostratigraphic setting of the orebody. Lastly, three aerial surveys were conducted in order to obtain orthoimagery and LIDAR data of the mining areas.