Osino holds a dominating land position in Namibia including 25 Exclusive Prospecting Licenses (EPL) covering nearly 8,000km². Outside the Twin Hills Gold Project (“Twin Hills”), regional exploration has capitalizing on the discovery of Twin Hills and the wealth of geological information generated. The regional exploration program includes four main regions including the Karibib District, Otjiwarongo, Sandveld and Otjikoto East project areas. These include 19 EPL’s covering about 6,500km² of fertile Damara aged (Pan African Neoproterozoic) structures and metasediments.
Osino has over the last 4 years revisited the entire and highly prospective, Damara Orogenic Belt with renewed exploration targeting and work programs. Now focused through the use of its proven proprietary calcrete sampling techniques, which have been refined since the Twin Hills discovery, to explore highly prospective but covered areas, previously not effectively explored. Geological and regolith mapping, detailed structural analysis, soil and bedrock (RAB) sampling and geophysical surveying are all methods used to define exploration drill targets.
Geological model and exploration approach (repeated in Twin Hills Gold section)
Osino is targeting gold mineralization that fits the broad orogenic gold model. Much of the historical exploration for gold in Namibia has not taken this approach. The key regional features and/or criteria of the orogenic gold model, and how they relate to the Namibian and Damara Orogenic Belt setting, are:
- Very large, long-lived and deep structures, including the Omaruru and Otjohorongo Lineaments, as well as the recently identified Karibib Fault.
- Large scale turbidite basins as a source of fluids
- Compressional tectonics (required for pumping the fluids out of the basins and through these large structures)
- Association with domes and basement highs
- Associated gold occurrences
a. Karibib District Project
The Karibib District Project (Twin Hills”) is held through 11 licences comprising approximately 153,206 ha of prime geology which straddles the heart of the known gold showings east and west of the town of Karibib.
This gold bearing district hosts the multi-million-ounce Navachab Gold Mine, Osino’s Twin Hills gold Project, and several known minor deposits such as the Onguati copper-gold and the Goldkuppe gold showings. Much of the area held by Osino has never been systemically explored as it is covered by calcrete and wind-blown sand.
Since Osino made the Twin Hills discovery in 2019, including the Bulge, THC and Clouds orebodies, there has been limited capacity for exploration activity outside of the resource drilling to fast-track project development. However, the Twin Hills ore bodies lie within a larger zone of mineralization and stretches from exploration targets at Terminal 1 in the west to Rheinsheim in the east (see figure below). Ground magnetic and induced polarization (“IP”) geophysical surveys, in conjunction with exploration drilling and calcrete sampling, have highlighted these anomalies which are systematically being followed up as part of the brownfields exploration program.
These brownfields targets are part of the Karibib District Project area, and make up the core of the Project which has been defined over more than 65km in strike length, stretching from the Goldkuppe Prospect in the NE to the Kranzberg Target in the SW.
The Karibib District Project is situated within the southern Central Zone of the Neoproterozoic Damara Supergroup, largely comprised of marbles and siltstones, which grade northwards into turbidite clastic sequences representing a continental shelf and basin margin at the time of deposition. These sediments are suspected to be the probable source of the gold mineralisation, and importantly, most of the known deposits, prospects and geochemical anomalies are associated with the southern and northern margins of this basin.
A major orogenic event between 550 Ma and 500 Ma closed the basin along a series of major ENE structures. Hydrothermal fluid movement was focused along these structures and produced widespread gold mineralization along second and third order structures developing within the marbles and clastic metasediments. Significantly, similar to other orogenic gold hosted systems, the understanding of this interplay between large structures and thick basin morphology has been the key to discovering gold deposits in these terranes.
Karibib District Exploration History
After the discovery of the Navachab Gold Mine in 1985 by Anglo American, regional exploration including stream sampling, soil sampling and limited drilling of known gold occurrences in the marbles of the Karibib Formation at Goldkuppe, Albrechtshöhe and Dobbelsberg was completed. In 2013 further diamond drilling at Goldkuppe and Albrechtshöhe was carried out by Helio Resources.
No further work was done in the area until 2017, when Osino commenced programs focused on the more fertile southern faulted margin of the basin and the Karibib Fault.
The eastern portion of this fault trend (which stretches over 20km) was soil sampled and a number of significant gold in soil and calcrete anomalies, including Twin Hills Gold Project, OJW and Rheinsheim, were discovered. The mineralization is associated with fault splay, jogs and bends, and is strongly structurally controlled – features all typical of fertile orogenic gold belts.
The entire extent from Twin Hills East to the Navachab Gold Mine property was then covered by a detailed 50m line spaced ground magnetic survey in an area that is completely covered by calcrete and sand.
The detailed ground magnetic data was of particular value in defining prospective structures and enabled support of the geochemical data collected at surface, therefore critical in helping constrain the generally covered geology in the Twin Hills area.
Current Exploration Program
n recent years the Company’s focus has been firmly on the Twin Hills discovery. Even so, the exploration team has been successful in discovering and defining brownfields resources which have added significantly to the overall resource, including Clouds (0.34 Moz) in 2020, Oryx and Kudu (0.21 Moz indicated) in 2021 and most recently Clouds West (0.02 Moz indicated and 0.02 Moz inferred).
Numerous, equally highly ranked targets along the Karibib fault now warrant similar in-depth investigation and drill testing. These include Dobbelsberg, Terminals / Eland, Puff Adder, THE, OJW Central, OJW South, Rheinsheim and Oasis/Wedge.
The brownfields exploration program for 2023 is designed to make new gold discoveries, with the primary focus on near-pit discovery. The four highest ranking targets scheduled for initial follow-up exploration are; Eland (directly west of Oryx), Twin Hills East (about 2.5km east along strike from Clouds), Puffadder (3km) and Dobbelsberg (5km) southeast and south of the Bulge pit, respectively.
Directly east of the THE target, on a more district scale, a syn-tectonic granite disrupts mineralization along the Karibib fault but soil sampling east of the intrusive shows that mineralization along the Karibib fault continues. Four high ranked targets were identified in this area between 2017-2019; OJW South, OJW Central, Rheinsheim and Oasis/Wedge. Initial reconnaissance work done included infill surface geochemistry, trenching and limited scout drilling. These targets now form part of the brownfields follow up program. The table below provides details on targeting vectors and work programs for all priority brownfields and district targets.
|Target Name||Target Support||Work Program||Priority|
|Twin Hills East||Magnetic and surface geochemical anomalies, structural complexity, thickening of preferential greywacke, historical drill support (10m @ 1g/t)||Drill testing||1a|
|Eland||Magnetic and surface geochemical anomalies, structural complexity, proximity to Oryx||Drill testing||1b|
|OJW South||Large concentrated gold-in-soil anomaly, associated with 2nd and 3rd order Karibib fault structures, gold in trenches||Structural mapping, trenching, drill testing||1c|
|Oasis / Wedge & Goldkuppe||Magnetic and surface geochemical anomalies, structural complexity, thickening of preferential greywacke, historical drill support (48m @ 0.7g/t)||Structural mapping, trenching, drill testing||2a|
|Rheinsheim||Geochemical gold-in-soil anomaly along Karibib fault, historic drilling||Structural mapping, drill testing||2b|
|OJW Central||Large geochemical gold-in-soil anomaly along 2nd order Karibib fault structures, gold in trenches||Structural mapping, trenching||2c|
|Puff Adder||Geochemical support – Au in soil, high strain hinge zone of regional dome structure||Expand soil sampling grid, structural mapping||3a|
|Dobbelsberg||Geochemical support – Au in soil, parasitic fold zone of regional dome structure, historic drilling||Structural mapping, drill testing||3b|
|Kranzberg / Klein Aukas||Magnetic and bedrock (RAB drilling) geochemical anomalies, strained structural corridor associated with fertile Karibib Fault.||Expand soil sampling grid, structural mapping, bedrock drilling||3c|
b. Otjiwarongo Project
The Otjiwarongo Regional Exploration Project is made up of nine licenses, including the Ondundu Gold Project, having a combined surface area of 2,657km² situated in central Namibia. The licenses lie roughly between the Company’s Karibib District and Otjikoto East Projects.
Osino’s regional exploration strategy includes the use of its proven proprietary calcrete sampling techniques, which have been refined since the Twin Hills discovery, to make new greenfield gold discoveries. in the figure above, areas indicated by stars represent ranked exploration targets with work programs scheduled for 2023 and beyond. Priority targets within the Otjiwarongo Project include Eureka, Moselle, Ondundu South, Epako Sud and Edendale. Geological mapping, detailed structural analysis, calcrete, soil and bedrock (RAB) sampling will be used to define exploration drill targets.
|Target Name||Target Support||Work Program||Priority|
|Eureka||Surface geochemical anomalies, fold interference, preferential Okonguarri Fm host rock (Otjikoto gold mine)||Structural mapping, drill testing||1a|
|Moselle / Libertas||Magnetic and surface geochemical anomalies, structural complexity, preferential Kuiseb – Karibib host rock||Extend soil and calcrete sample grids, trenching, drill testing||1b|
|Edendale||Magnetic and surface geochemical anomalies following fertile regional 1st order structure, in Kuiseb Schists||Infill soil grids, structural and lithology mapping||2a|
|Ondundu South||Structural strike extent to Ondundu mineralisation, surface geochemical anomalies||Structural mapping, trenching||2b|
|Epako Sud||Geochemical gold-in-soil anomaly along fertile regional structures, historic gold mining||Trenching, drill testing||3a|
|Etekero||Bedrock geochemical gold anomaly, Magnetic structural anomalies||Extend geochem sample grids, drill testing||3b|
Osino continues to identify, and aims to further consolidate, areas of key regional structural and stratigraphic targets in this part of the Damara Belt. The licenses are focused on specific regional fault, fold and lithological targets with similarities to other gold deposits and occurrences found in Namibia, while also fitting the general targeting criteria of the orogenic gold model followed by the Company.
c. Sandveld Project
Osino has recently staked a large new land package approximately 100km to the east of Twin Hills, a contiguous block of three current and two licences still under application. The Sandveld Project will make up a combined project area of 3,575km² covering what Osino believes to be the eastern extension of the fertile Karibib Fault, which is host to Osino’s Twin Hills discovery (3.1 Moz in Indicated & Inferred Resources).
The land package also covers the Mon Repos Thrust which is believed to be instrumental in the formation of the Navachab Gold Deposit (estimated 8 Moz historical gold resource comprising approximately 2 Moz in past production and approximately 6 Moz in remaining total endowment).
Most of the Sandveld Project is covered by calcrete and wind-blown sand which has rendered traditional exploration methods ineffective, and the entire area remains almost completely unexplored. Surface work is planned to start in 2023, using a combination of in-house sample collection and analysis techniques developed by the Company.
d. Otjikoto East Project
The Otjikoto East Gold Project consists of one license (with another currently being under application) covering approximately 381km². The license areas include approximately 30km of strike length with prospective geology similar to that which hosts the Otjikoto Gold Mine (owned by B2Gold Corp.), less than 10km to the west of the Company’s licenses.
Osino regional exploration is focused on a number of specific regional fault, fold and lithological targets with similarities to Otjikoto, and which occur along similar trends while also fitting the general targeting criteria of the orogenic gold model followed by the Company.
History of B2 Gold’s Otjikoto Gold Mine
The Otjikoto gold deposit was discovered in 1996 by Avdale Namibia, when they drilled a prominent magnetic anomaly during a regional base metal exploration programme in an area of flat, featureless calcrete covered scrub. After the discovery, areas of similar stratigraphy to the east and south of Otjikoto were explored using geophysical methods, specifically airborne magnetic and electromagnetic surveys, of which the most prominent anomalies were tested with wildcat diamond holes and in some cases with RAB drilling. None of the geophysical targets drilled were positive and Avdale relinquished the Otjikoto East area in 2010.
The Otjikoto deposit has now been demonstrated to host a resource in excess of 3 million ounces and growing with mineralisation found to be largely hosted by schists belonging to the Okonguarri Formation. Gold mineralisation is found just below the contact with the marbles of the Karibib Formation.
These stratigraphic contacts have focused Osino’s exploration to date; however, the uppermost Kuiseb Formation, which forms so much of the host rock stratigraphy at Twin Hills, underlies parts of the license areas and is also prospective.
Otjikoto East Project Exploration History
Osino started regional work at Otjikoto East in October 2017, initially reprocessing the regional magnetic data to assist with lithological mapping under the calcrete cover and remote sensing regolith mapping to best constrain the geomorphological setting of geochemical results. High priority areas were selected on the basis of stratigraphy and structural complexity and a campaign of calcrete and termite mound sampling was initiated.
Calcrete sampling has been highly successful in Western Australia and has led to the discovery of gold deposits under cover. Anthill sampling has been successful in exploring for gold in Zimbabwe as well as West Africa. These methods of sampling have been applied by the Company and both calcrete sampling as well as anthill sampling have been successful leading to the discovery of a number of gold anomalies. Further geological interpretation has been combined with magnetic mapping to identify large-scale, potentially gold fertile structures as well as enabling a delineation of the prospective stratigraphy.
As the Otjikoto East region has very limited outcrop and the interpreted geology is essential to prioritize and direct activities on the ground, magnetic mapping has become crucial in identifying the large-scale, potentially gold fertile structures as well as the prospective stratigraphy.
Otjikoto East Project Current Exploration Program
Given the positive historic results the project will be prioritised for further work in 2023 with the Fairview, B2 East and the Devon targets scheduled for follow-up work programs.
Fairview was discovered as multiple gold anomalies in anthill samples adjacent to an interpreted dome structure. Subsequent pitting and rock chip sampling of limited quartz vein outcrop produced two positive assays of 1.16 and 0.90 ppm gold, along with anomalous silver and copper. This is regarded as a priority target for drill testing.
B2 East and Devon targets are desktop generative at this stage with no fieldwork done to date. B2 East has structural and lithological characteristics similar to those hosting gold mineralisation at the nearby (12km) Otjikoto Gold Mine. Devon represents a regional scale structural splay or positive flower structure identified from interpreting regional airborne magnetic data. The splay represents a similar structural setting to the Twin Hills Gold Project, where dextral rotation within a restraining bend along the Karibib Fault resulted in the development of a significant fracture/plumbing for the gold endowed hydrothermal fluids.