Karibib Regional Exploration
Regional mapping and re-interpretation of the aeromagnetic data has identified a large, previously unmapped, deep regional structure – now named the Khan River Fault. This structure can be traced over 40km and has several gold-in-soil anomalies along it and on splays leading off it. Osino’s exploration activities during 2017 were focussed along this major structure between the companies’ Goldkuppe project and the Navachab Gold Mine. The southwest portion of the Khan River Fault and the Goldkuppe-Onguati trend will be explored during 2018.
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. There are two major producing gold mines within the Damara and several well-known smaller deposits which have been mined or evaluated in the past including Ondundu, Onguati, Sandamap and Epako.
Stratigraphic Column for Damara Lithologies in Karibib Project Area:
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. Known gold occurrences in marbles at Goldkuppe, Albrechtshöhe and Dobbelsberg were followed up with soil sampling as well as limited drilling. Detailed follow up at Goldkuppe (see separate summary) and Albrechtshöhe was carried out by Helio Resources in 2013. No further regional work was done.
Work Completed by Osino to Date
Osino started regional work on the Otjimbojo licence (EPL3739) at the end of 2016. Initial review of the historical data and orientation work indicated that most of the area had not been adequately sampled or not sampled at all. A small but promising soil anomaly at Twin Hills had never been followed up. A decision was made to undertake a systematic soil sampling and mapping exercise paying careful attention to regolith effects. By the end of 2017, a total of 13,718 soil samples and 275 rock samples had been collected and a new detailed geology map created. This work, together with in – house reprocessing and interpretation of the aeromagnetics led to the discovery of the regional scale Khan River Fault which has a number of large coherent gold anomalies along it. The Khan River Fault lies within the Kuiseb turbidite basin which was previously not considered prospective in this area.
The largest of the gold anomalies is Twin Hills where the extent is currently 3,000 x 300m and still open to the west where it is hidden under calcrete. Two further large targets exist to the east of Twin Hills namely Okapawe (3000 x 100m+) and Okapawe Dam (700m long and open to the west. These three anomalies contain high tenor soil assays (>100ppb gold) and exhibit spatial continuity. The mineralisation appears to be hosted by quartz-sulphide veinlets within biotite schists and quartz biotite schists. The mineralisation is structurally controlled by second order structures and pressure shadows adjacent to syn-deformational granites. There are also several other smaller – scale anomalies which were discovered during 2017 including the promising Wedge prospect which appears to be hosted by a large-scale shear within Arandis schists.
Work Planned for 2018
RC drill traverses with additional diamond drilling where appropriate, have been planned for Twin Hills, Okapawe and Okapawe Dam starting Q2 2018. A second phase of drilling is planned for later in the year. The soil sampling programme will continue in Q1 2018 to the west and south west of Twin Hills as well as the area between Twin Hills and Okapawe. This next phase of sampling will take approximately 6 months.