Goldkuppe Historical Drill Plan & Intersections
Goldkuppe & Extensions
Goldkuppe is an advanced project covering gold mineralisation within carbonate rocks belonging to the Karibib Formation over an area of 3,400 x 700m in extent. The Karibib rocks are folded into an overturned isoclinal antiform plunging shallowly to the north east with limbs dipping southeast. This antiform has later been refolded along north – south axial planes with fold axes plunging steeply to the south.
Since the mid 1980’s a series of geochemical, geophysical and geological surveys have defined several gold and copper anomalies, magnetic anomalies, chargeability anomalies and geologically generated targets in the Goldkuppe area. Approximately 10,000 m of RC and diamond drilling has been conducted by at least three previous operators and explorers in the Goldkuppe area. Mineralisation is shallow and some significant high-grade (3 – 30g/t Au) zones occur within the lower grade envelope.
Highlights of historical drilling are as follows:
DDH OJD009: 18m of 1.0 g/t Au, 0.14% Cu and 7.5 g/t Ag ( from 9 – 27m)
DDH OJD012: 28m of 1.8 g/t Au and 5g/t Ag (from 37 – 65m)
DDH OJD001: 7m at 9.0 g/t Au, 73 g/t Ag and 4.43% Cu, from 54 – 61m.
DDH OJD008: 6m at 5.3 g/t Au, 23 g/t Ag, from 48 – 54m.
DDH OJD013: 4m at 11.6 g/t Au from 30 – 34m.
The very shallow depth of several of these intersections is striking. Many of the historic RC and diamond drill holes were of a reconnaissance nature and were terminated at distances of less than 50m sub-surface. All of the mineralized interval lengths within these drill holes are drill indicated lengths as the geometry of the mineralized zone has not been defined.
The combined surface geochemical, geophysical and geological data, as well as the results from several surface RC and diamond drill programmes indicates that subsequent exploration within the Goldkuppe area is well warranted.
The Project is situated within the Southern Central Zone of the Damara Supergroup in central Namibia between the towns of Karibib and Omaruru. The Damara Supergroup is Neo-Proterozoic in age and is comprised of continental margin carbonates and silts which grade into turbidite sequences representing continental shelf and basin deposits. The Damara underwent a major orogenic event at 550 – 500Ma when the sea closed along a series of major ENE structures. Hydrothermal fluid movement produced widespread gold mineralisation within the carbonates and schists.
The Karibib Formation is underlain by Arandis schists in the core of the antiform in the Goldkuppe area. The Arandis schists are the lithologies that hosts most of the Navachab gold mineralisation. There are granitic intrusions to the east of Goldkuppe and pegmatitic dykes, sills and blows are common. The carbonate rocks have been altered to skarn in irregular haloes – diopside and tremolite are common alteration minerals.
Stratigraphic Column for Damara Lithologies in Goldkuppe Project Area
There are two major producing gold mines within the Damara – Navachab and Otjikoto – and several well-known smaller deposits which have been mined or evaluated in the past including Ondundu, Onguati, Sandamap and Epako.
The gold mineralisation at Goldkuppe is hosted primarily by dolomite with minor zones in the underlying white and banded marbles – all within the Karibib Formation. The higher grade mineralisation is primarily associated with massive sulphides (pyrite, chalcopyrite) on or adjacent to the contact between dolomite and underlying white marble. Lower grade disseminated mineralisation occurs within the skarn alteration zones which are often magnetic due to the presence of pyrrhotite. These zones can be 20 or 30m wide but are generally less than 1g/t and can be less than 0.5g/t. Gold also occurs in quartz – sulphide veins which are 1 – 10cm wide. The mineralisation is strongly structurally controlled with the massive sulphide zones occurring in the north – south orientated fold noses as saddle reefs and foliation parallel boudins.
Goldkuppe was first discovered during the German colonial period but no formal exploitation took place. After the discovery of the Navachab gold deposit in 1984, Anglo American carried out a rapid regional exploration programme using primarily stream sampling and targeting similar stratigraphic horizons and basement domes. The known gold occurrence at Goldkuppe was drilled by Anglo American in 1988 and again in 2003.
Helio Resources was granted the licence in 2007 and signed a Joint Venture deal with Desert Minerals to carry out exploration. Desert Minerals drilled 18 RC and 3 diamond holes in early 2008 but were forced to close down in October of 2008 due to the Global Financial Crisis. Helio restarted exploration in 2011 with a detailed soil programme over Goldkuppe at a spacing of 100 x 25m and then an extension grid to the northwest at 200 x 25m. These results were used as the basis for the later drill programmes. They also carried out detailed geophysics including ground magnetics, electromagnetics and IP. Students from Cardiff University were contracted to do structural and mapping work during 2011 and 2012.
Between 2010 and 2013 Helio carried out drill programmes of RC and diamond drilling. The RC programme focussed on extensions of the known mineralisation as well as a series of 200m line spacing east – west traverses. The collars were located at 50m intervals with scissor holes drilled east and west at each collar. Helio also drilled twin holes of the best Anglo intercepts in the central part of the target.
Work Completed by Osino to Date
Osino started work on the Goldkuppe project towards the end of 2016. When the project was acquired from Helio Resources, there was an inherited drill programme in place to drill out the central portion of the target with a view to assembling an initial resource. After 25 holes, Osino decided to curtail the drill programme as it became apparent that the historical understanding of the mineralisation and structure was poor and that further work was required before an effective drill-out could take place.
During 2017, all historical core and chips were re-logged and a simpler more coherent geological model was put in place. Structural interpretation was carried out on the core and at surface. A highly detailed surface map was compiled and first-pass Leapfrog modelling carried out.
In November 2017, the Goldkuppe extensions were drilled at North End, Calidus, Spang and Oasis with a total of 24 RC holes for 2,569mm. These targets are all based on surface geochemistry and rock chip sampling of gossans at surface. Drill results are currently awaited.