A study on the mothballed Khusib Springs copper-silver mine in Namibia recently acquired by junior explorer Golden Deeps (ASX: GED) has identified remnant mineralisation on the margins of mined stopes and at depth.
Geological consulting group Shango Solutions conducted the study, which aimed to validate historic drilling data and digitally-capture hardcopy mine plans including that of the old underground development and stopes with a view to assessing the potential to mine any leftover ore.
The data was imported into a 3D mine software package to allow visualisation of the orebody and to assist targeting.
South Africa-based Shango modelled both the copper and silver mineralisation where high silver grades averaging up to 585 grams per tonne were reported during the mine’s operation from 1995 to 2003.
Shango’s study identified remnant zones of copper-silver mineralisation on the margins of the mined stopes at Khusib Springs – possibly left behind due to relatively low copper grades and prices at the time.
A priority zone was identified within 100m of surface and is believed to be amenable to reverse circulation drilling.
Down plunge of the main orebody, a second priority zone was also found with underground mining revealing it dips steeply and pinches out at depth.
Deep wide-spaced drilling was conducted by former owner Ongopolo Mining Ltd to intersect possible extensions.
Some of those holes hit mineralised zones with elevated copper-silver grades which Golden Deeps said appear to represent a faulted offset of the orebody.
The company said electromagnetic surveys should be successful at locating off-hole conductors which could be tested with drilling.
Located near the town of Grootfontein in Namibia, Khusib Springs was an unusually high-grade, relatively small copper-silver mine with a pre-mining resource of more than 300,000t at 10% copper, 1.8% lead and 584g/t silver.
The deposit was discovered in the early 1990s through mapping and drilling.
Previous notable drill results from Khusib Springs were 4.5m at 35.19% copper, 3.67% lead, 2.23% zinc, and 2,090.91g/t silver from 30m; and 14m at 8.12% copper, 0.75% lead, 0.52% zinc and 385.06g/t silver from 37m.
Mining began in 1995 and ceased in 2003 due to a low copper price at the time and the depletion of easy-access, high-grade ore.
Khusib Springs has been described as a steeply plunging pipe-like lens hosted by limestone and is considered to be comparable to the nearby Tsumeb mine, which was closed in 1996 after 91 years production.
Tsumeb was one of the world’s major copper producers during its time, churning out a total 30Mt of ore grading 4.3% copper, 10% lead and 3.5% zinc during its life.