A variety of genetic models, ranging from magmatic through hydrothermal to syngenetic, have been postulated in the past for the formation of gold deposits in the Pine Creek Geosyncline. Gold and base metal mineralization in the Pine Creek Geosyncline is commonly associated with granite intrusions and have often been classified as high temperature contact aureole deposits. A secondary host rock control has also been suggested due to the association of gold mineralization with carbonaceous metasedimentary rocks, such as at Cosmo Mine.

Native gold is the main mineralization mineral and is commonly present as micron sized grains; coarse nuggets are rare. Gold is commonly associated with pyrite, arsenopyrite and pyrrhotite and in places with minor base metal sulphides. Quartz, chlorite, sericite and carbonates are the common gangue minerals in the gold-quartz deposits.

All gold deposits in the Northern Territory show some structural control at the regional and deposit scales, with most deposits within the Pine Creek Orogen trending northwest southeast.

Base metal mineralization in the Pine Creek Orogen strike significantly differently than the gold veins, suggesting different discrete mineralizing events. They are syngenetic.

Cosmo gold mineralization is hosted across a stratigraphic sequence (‘Cosmo Mine Sequence”) that lies between a major dolerite sill (‘Zamu’ dolerite unit) and a thick package of high sulfide, graphitic mudstone (‘Pm ........

The Company is currently mining the Cosmo Deposit as an underground mine at a current depth of 600mRL. The Cosmo workings are accessed via a decline commencing from the southern wall of the Cosmo open pit. The mining activity at Cosmo has progressed from the Eastern Lodes utilizing Avoca-style cut and fill stoping to the Hinge Zone and Western Lodes where uphole open stoping is employed.

Ore was previously mined by a combination of Modified Avoca and Long-hole Open Stoping when isolated stopes were extracted. Mining is now focused on the Hinge Zone and Western Lodes where the uphole open stoping will speed up access to stope ore as upper stopes will be mined without the requirement to backfill.

Uphole Open Stoping is sequenced from the top down. As soon as the drill drive is completed, Stope development can begin. Rib pillars are left at intervals along the length of each panel to support the hangingwall without the requirement of back filling. Sill pillars are not required to regulate stope development. All underground production mineralization is trucked via the decline to the surface ROM stockpile adjacent to the Cosmo open pit. Mineralization is then loaded into on-highway haul trucks to be transported 67km to the Union Reefs processing plant.

Development waste is used for stope backfill as dictated by the production schedule. Waste not immediately required for backfill is typically stockpiled underground close to stope backfill location ........

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