Summary:
Theta Gold team is active on site to deliver into a steady state of production initially from four existing mines, Beta, Frankfort, Clewer-Dukes Hill-Morgenzon (CDM), and Rietfontein.
The Project Areas are situated within the Sabie-Pilgrims Rest Goldfield. Gold mineralisation occurs within shear zones located within sedimentary host rocks of the Transvaal Supergroup.
Epigenetic gold mineralisation in the Sabie-Pilgrims Rest Goldfield occurs as concordant and discordant (sub-vertical) veins (or reefs) in a variety of host rocks within the Transvaal Drakensberg Goldfield, and these veins have been linked to emplacement of the Bushveld Complex.
Mineralisation in the region occurs principally in concordant reefs in flat, bedding parallel shears located mainly on shale partings within the Malmani Dolomites. These bodies are stratiform, and are generally stratabound, and occur near the base of these units.
The discordant reefs (or cross-reefs) are characterised by a variety of gold mineralisation styles. At Rietfontein, a sub-vertical quartz-carbonate vein occurs which reaches up from the Basement Granites and passes to surface through the Transvaal. They are found throughout the Sabie-Pilgrims Rest Goldfield, and are commonly referred to as cross reefs, blows, veins, and leaders and exhibit varying assemblage of gold-quartz-sulphide mineralisation generally striking northeast to north-northeast. They vary greatly in terms of composition, depth and diameter. In addition to the above, more recent eluvial deposits occur on the sides of some of the hills and are through to represent cannibalized mineralised clastic material resulting from the erosion of underlying reefs. Gold mineralisation is accompanied by various sulphides of Fe, Cu, As and Bi.
The orebodies considered in the FS are described as thin, sheet-like near horizontal deposits. The reefs considered for extraction through the underground operations at Beta, Frankfort and CDM, namely the Beta Reef (Beta Mine), Bevetts Reef (Frankfort Mine) and Rho Reef (CDM) are all concordant reefs that dip shallowly westwards between 3°and 12°. At the Rietfontein Mine, the Rietfontein Reef occurs as a subvertical hydrothermal vein striking north-northeast and fills a narrow 1-3 m wide fracture in basement granite.
Beta
The Beta Reef occurs as a sub-horizontal or hydrothermal typical “flat reef” quartz-carbonate vein which strikes north-northeast, dips at about 3° to 7° to the west and pinches and swells down dip as well as along strike. The reef varies in width from waste-on-contact to nearly 3 m with a mean reef width of between 20 cm to 30 cm and is stratigraphically located within the dolomite of the Eccles Formation within the Malmani Subgroup of the Transvaal Supergroup. The gold-bearing material is mainly associated with pyrite with trace chalcopyrite with a minor presence of graphitic and carbonaceous material.
The Beta Reef vein has been prospected to depths of about 550 m below surface by historical as well as more recent drill holes. The only available information is that which is available in the form of annotations on plans and various MS Excel™ spreadsheets. The deepest underground development reaches a depth of 360 m below surface. Exploration activity indicates the presence of a pay shoot towards the east-southeast of the current westernmost workings.
The Beta Reef quartz vein follows the regional trend of bedding on a north-northeast to south-southwest strike orientation. It has been traced for nearly 2 km on strike and 2.5 km on dip and mined for at least 1.5 km down dip in the area of Beta Mine.
The Beta Mine is split into an eastern and western section by the 30 m thick north-northeast to southsouthwest trending Beta Dyke which is thought to be diabasic in nature (of the late Vaalian age belonging principally to the Bushveld Complex) and intruded into the Transvaal Group. The dyke exhibits a scissor displacement on the Beta reef where in the north displacement is approximately 2 m down to the west. In the south this displacement increases to approximately 25 m to the west.
Minor dykes and faulting occur within the Mine trending along the regional north-northeast to southsouthwest trending lineaments and generally have negligible displacements.
Frankfort
At the Frankfort Mine, the Bevetts Reef occurs as a concordant to sub-concordant reef. The Bevett’s Reef is developed at the interface between the Bevetts quartzite and the overlying Pretoria shales. The reef consists of a quartz-carbonate vein, which can vary in thickness from a contact to in excess of 200 cm. Evidence of duplex thrusting is present, which may have served to eliminate the reef horizon in some areas and duplicate it into a thick package in other areas. Reef mineralogy is comprised of coarse euhedral sulphide crystals. These coarse sulphides are predominately pyrite, arsenopyrite and lesser tetrahedrite. Massive chalcopyrite is common. The mineralisation is commonly banded with barren milky quartz and lesser calcite between the sulphide bands.
Below the Bevetts Reef, a 100 cm thick quartzite unit is developed. Below this quartzite, the Bevetts Conglomerate, comprising rounded to sub–angular chert clasts, is sporadically developed. Below this, the thin dolomitic Rooihoogte Formation is present before passing into a 60 m thick lava unit, which contains amygdales at the top of the unit.
CDM
At CDM, the Rho Reef hosts gold mineralisation and has a general dip direction of 5° to 7° to the west and strikes in a north–south direction. The reef occurs approximately 24 m below the base of the Bevett’s unconformity, which marks the end of the dolomite succession and the beginning of the Pretoria Group. The Rho Reef itself consists of an Upper Rho Reef and a Lower Rho Reef separated on average by 2 m of argillaceous dolomite. Below the Lower Rho Reef there is a sill developed approximately 5 m in the footwall ranging from 5 m to 18 m thick. A shale band varying from 5cm in the north to 60cm in the south is developed 3 m below the Lower Rho Reef. Above the Upper Rho Reef, a unit termed the silver shale is developed 3 m in the hanging wall and is between 50 cm and 100 cm thick. Above the silver shale, a hanging wall sill is developed that ranges from 18 m to 22 m thick. The Bevett’s conglomerate unconformably overlies this hanging wall sill.
Faulting generally trends NNE to SSW is normal and sub–vertical. Displacements are in most cases less than 3 m. Dykes occupy pre-existing fault planes and either one or both contacts are strongly faulted. Dykes follow the trend of the faulting and in most cases faults and dykes are water-bearing, though the inflow is not excessive.
The resource model is however based on one reef only, referred to as the Rho Reef. It is uncertain if the historical sampling captured is the upper or lower reef.
Rietfontein
Another style of mineralisation occurs at the Rietfontein Mine, where the Rietfontein Reef occurs as a crossreef in the basement granites. It penetrates the overlying Black Reef Quartzite for a short distance before petering out. The granite surrounding the quartz vein is heavily decomposed as a result of the hydrothermal fluids and influx of surface water along the outcrop trace of the quartz vein. The sub-vertical hydrothermal quartz vein strikes north-northeast and fills a narrow 1-3 m wide fracture in basement granite. The quartz vein has been traced over 16 km on strike and mined for 3 km along its strike length. The gold-bearing material and the gold are associated with pyrite and trace arsenopyrite, chalcopyrite and bismuth. The vertical vein has been prospected to depths of 400 m by historical drillholes, the only information is annotations on plan. The deepest underground development is 320 m below surface. There is no indication of the vein closing out at depth giving room for exploration of the depth extensions.