Summary:
Dokwe is located within a covered Archaean Greenstone Belt, extending from the border with Botswana (Maitengwe greenstone belt) and linking up with the Bulawayo-Bubi Greenstone Belt to the east. The Archaean greenstone units are overlain by Karoo and Kalahari sedimentary units of up to 25-40m in thickness. The east-northeast striking greenstone belt has been complexly folded and thrust-faulted and is dissected by a series of major sub-parallel sinistral shear zones.
At the Dokwe Gold Project area, the barren sedimentary cover is dominated by calcrete, with a few metres of sand at the surface, and mudstone and sandstone located towards the base. The basement Archaean volcanic sequence comprises a series of quartz-rich volcaniclastic units, tuffs, and agglomerates, that grade into felsic irregular rhyolitic flows; intermediate vesicular dacite; agglomerates and andesites. The volcanic sequence has undergone greenschist facies metamorphism and deformation. The sequence appears intruded by near syn-depositional quartz porphyries and later by dolerite. While brittle-ductile deformation occurs throughout the deposit, somewhat more brittle deformation, characterised by fracturing, is common in felsic tuff and porphyry units whilst rather more ductile deformation characterises the dacitic and andesitic units.
The Dokwe deposits comprising Dokwe North and Central. The Dokwe North and Central deposits are strongly structurally controlled, occupying two distinct structural domains within a broader ENE trending shear zone.
Dokwe North
The Dokwe North deposit consists of a sequence of Archaean intermediate to felsic volcanic rocks, interbedded with layers of agglomerate and tuff. A quartz-feldspar porphyry intruded into the upper part of the sequence. The Archaean rocks have been folded, metamorphosed to greenschist facies and sheared. Gold is particularly concentrated where a sub-vertical shear zone interacts with lithological contacts, which typically dip towards the southeast at a moderate angle. All Archaean rock types exhibit some degree of gold mineralisation, with the principal host rocks being dacite, tuff and porphyry. Coarse visible gold is a characteristic feature of this deposit, with higher-grade zones developing along discrete shear zones.
The Dokwe North is characterised as a large low-grade deposit containing relatively few quartz veins, with several very highgrade zones including visible gold developed within a sheared and folded volcaniclastic sequence. The gold mineralisation is associated with silicified zones containing thin quartzcarbonate pyrite veins and narrow shears. There is also an association with strongly disseminated, fine-grained pyrite in the host rocks. Much of the economic gold mineralisation occurs in the dacitic unit and in the overlying felsic tuff, with lesser mineralisation within quartz porphyry and andesitic units.
The geology of Dokwe North primarily consists of a sequence of Late Archean-aged greenstone volcaniclastics. These include dacite-to-andesite flows featuring amygdaloidal rich horizons, interbedded felsic tuffs, agglomerates, and irregular rhyolite flows.
The sequence is intruded by earlier quartz-feldspar porphyries and later altered dolerite. Brittle deformation, characterised by fracturing, is common in felsic tuff whilst more ductile deformation characterises dacite and andesite.
A major brittle fault, the “Western” fault is post-mineralised structure dissecting offsetting mineralisation.
The main Dokwe North orebody occurs within a NE-SW trending shear zone that displays a central core with intense foliation and mylonitisation of the host rocks.
Primary gold mineralisation at Dokwe is preserved as free gold and occasionally as inclusions in quartz veins, micro-fractures in pyrite, and other open-space micro-features.
The mineralisation is primarily structurally controlled and associated with the intensity of shearing and with lithological contacts. Visible gold has been documented multiple times and is often associated within the foliation planes formed by shearing.
Overlying all the basement stratigraphy is a sequence of barren sedimentary rocks.
Dimensions
The orebody is 780m along strike, 470m across strike (across the thickest portion of the deposit), and the depth from the surface is between 42m and 320m.
Dokwe Central
Dokwe Central is a smaller, higher-grade pipe-like deposit containing abundant quartz veins and several steeply plunging high-grade zones. Mineralisation is contained within a series of strongly sheared intermediate chlorite schists and biotite-chlorite schists in a covered Archean Greenstone Belt, extending from the border with Botswana (Maitengwe Greenstone Belt) and linking up with the Bulawayo-Bubi Greenstone Belt to the east. The Archaean greenstone units are overlain by Karoo and Kalahari sedimentary units of up to 25-40m in thickness.
Mineralisation appears to be dominantly constrained within intensely sheared and brecciated zones, and in association with disseminated sulphides (dominantly pyrite).
The defined mineralisation extent is abruptly terminated against a package of sedimentary rocks to the north, marking a major east-west trending fault.
Dimensions
The orebody is 260m by 200m across and the depth from the surface is between 25m and 350m.