Summary:
Tanami consists of sediment hosted sheeted quartz vein mineralization.
Mining operations are predominantly focused on the Callie and Auron ore bodies in the underground mine at Dead Bullock Soak (“DBS”).
The Project lies in the eastern part of the Early Proterozoic Granites-Tanami Inlier. The basement geology of the Project is predominantly comprised of the sedimentary rocks of the Tanami Group. The remaining basement is predominantly composed of granitic intrusions. The Tanami Group consists of two Formations; the Dead Bullock Formation and the overlying Killi Killi Formation.
The Killi Killi Formation is the most widespread unit across the Project tenements. It is dominated by a thick interval of turbidites, with a felsic volcanic component and a distinctive unit of jasper chert.
The Dead Bullock Formation has been informally divided by the geologists of the Project into two Members; the Callie Member and underlying Ferdies Member. These units host all the known gold mineralisation on the project tenements.
At DBS there are two sub-units (Members) within the Dead Bullock Formation; the Callie Member (which includes SHIM, Orac and the Callie Laminated Beds) and the Ferdies Member (which includes the Lower Auron Beds). Post-mineralization faulting has repeated parts of the stratigraphy and mineralization.
The Callie mineralization is developed in the DBS anticlinorium which is an upright isoclinal fold with local complex parasitic folding. Mineralization is present in the Lantin and Callie Anticlines, the Challenger Syncline and their respective limbs. The Auron deposit sits stratigraphically below the Callie deposit. The Federation deposit represents an un-mined mineralization envelope hosted predominantly within the hinge and southern limb of the Federation Anticline which is parallel to the Callie and Lantin Anticlines.
The Callie deposit has a complex shape, which is a function of the difference in strike of the quartz vein corridors (070°) and the plunge of the folded sequence (100°). The gold mineralization occurs in steeply dipping sheeted veins within the folded sequence. The orientation of the veins is 65° towards 154°, hence they are locally referred to as “70/70” veins. Vein density in the ore zone averages five veins per meter; however, it can reach more than 12 veins per meter in “corridors” that range in thickness from 20 to 50 meters (m). The width of mineralization varies significantly due to the interaction of the fold, fault and quartz vein corridor geometries, at its thickest point it is ~200 m wide in the hinge of the Callie Anticline. Mineralization has a down-plunge extent of at least 2,800 m from the surface to the easternmost deepest drill intercept. The mineralization currently remains open at depth. Gold is characteristically nuggety and occurs exclusively within the veins as grains from submillimeter sizes through to >20 millimeters (mm).
Auron shares the same structural, metamorphism, alteration and vein generations as Callie, and the mineralized quartz vein corridors that control the Callie mineralization are continuous through Auron. The majority of the economic Auron mineralization is represented by the Callie-style 70/70 sheeted vein mineralization. Auron shows a similarly complex shape as the Callie deposit due to the intersection of the folded sequence and the vein corridors. This is further complicated by fault repetitions. The Auron mineralization has been demonstrated to have a plunge extent of at least 2,500 m and remains open to the east. Like Callie, the width of the Auron mineralization varies significantly due to the interaction of the fold, fault and quartz vein corridor geometries, at its thickest point it is ~150 m wide. It gradually thins out up-plunge and is attenuated on the fold limbs.
Gold at Federation is hosted by a similar sheeted 70/70 vein set. The Federation mineralization has been demonstrated to have a plunge extent of at least 1,000 m. Mineralization has reduced widths relative to intersections within Callie and Auron.
Exploration drilling conducted during 2015 confirmed a new discovery in the Federation Anticline. The new orebody, referred to as Liberator, was similar to Federation in its structure and geometry but hosted in a rock mass similar to that of the Auron orebody.
Three types of gold mineralization have been recognized within the Project area:
• Callie-style mineralization is characterized by coarse and readily visible gold occurring in quartz veins hosted in carbonaceous siltstone. These contain very minor sulfides and are generally discordant to bedding. Mineralization is in subparallel, sheeted quartz veins within a structural corridor. Example deposits and prospects include Callie, Auron and Federation;
• Villa-style mineralization is associated with Au-sulfide (arsenopyrite, pyrite and pyrrhotite) ± quartz ± carbonate veins in BIF and chert. The veins follow a stratigraphic horizon of iron-rich, cherty metasedimentary rocks within the Dead Bullock Formation. While generally associated with veining, a vein is not necessary for gold deposition and gold may be disseminated throughout the host. Example deposits and prospects include Triumph, Colliwobble, Sleepy Hollow, Dead Bullock Ridge, and Villa–Fumerole;
• East Bullakatchie mineralization that developed in Au–carbonate–sulfide ± quartz veins. These are unique to the East Bullakitchie deposit and occur as concordant and discordant veins within metamorphosed sedimentary rock, which probably had a carbonate precursor.