Post-Conference Field Trip | FT07 View all field trips
The Iron Oxide Copper Gold (IOCG) Vein System of the Onganja Mine, Windhoek District
Description
The Onganja Mine, with a 120-year history, is located 65 km northeast of Windhoek. The orebodies comprise a post-orogenic, Neoproterozoic, iron oxide copper-gold (IOCG) sheeted vein complex, hosted by Kuiseb Formation quartz-plagioclase-biotite schists, within the Southern Zone of the Damara orogen. The genesis of the vein systems has never been satisfactorily explained, but they may have been derived from the multi-phase intrusions of the S-type Donkerhuk batholith, lying to the north.
The mine is currently being brought back into production. Underground development on the VT8-West section, reached via an inclined shaft, exposed a high-grade manto in readiness to commence production. New underground development is planned at the MY4-South section, where a second feeder vein-manto was discovered during a 2023 exploration drilling program. Ore beneficiation is to be carried out by conventional crushing, milling, and flotation circuits, currently under advanced construction.
There will first be a general introduction to the geological setting of the mesothermal, Neoproterozoic Onganja orebodies, the nature of the Iron Oxide Copper Gold vein-hosted mineralization, and a short history of mining activities in the area.
This will be followed by visits to trenched areas of outcrop where the typical IOCG style of reddish, iron-dusted albite and albitized wallrock schists are present, as are chalcopyrite and chalcocite-derived gossans in the brecciated host feeder veins.
Out of interest, outcrops of the remarkable, magnetic epidosite metavolcanics, which pre-date the Onganja orebodies, will be visited. This unit acts as a marker horizon delineating the outer limbs of the plunging antiform which hosts the Onganja orebodies. An underground visit will be undertaken to look at an exposure of the massive chalcopyrite manto ore. Hardhats and cap lamps will be provided.
Examples of host-rock alteration and mineralized intersections of chalcopyrite ore obtained during a reverse-circulation drilling program will be viewed in the drilling samples storage facility.
Visitors should have the following items: Field boots, hardhats, and other personal items such as field bag and rock hammers, as they may require. Underground cap lamps and hardhats will be provided on site.
About the Leader
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Robert Carr
General Manager, Onganja Mining Company (Pty) Ltd
As an exploration geologist, he started with Falconbridge of South West Africa, in 1971. The focus was on detailed mapping of basement, shear-hosted copper and fluorspar occurrences in the Outjo District and general base metal exploration work in the Warmbad District. The following years were spent carrying out exploration for his own account, which included base metals, tin-bearing pegmatites and industrial ores, such as barytes and wollastonite.
His interest turned to a small-scale, limited but successful underground copper mining operation in the 1980s, followed by the development of a quartz quarry, producing optical grade material for the European market. After this, and for a long period, he stepped away from mining exploration and specialized in groundwater exploration for secondary aquifers in arid, hard rock terrain. During this period, he was part of the team that successfully pioneered the artificial recharge of the Windhoek Wellfield fault-hosted aquifers..
In the late 1990s, he acquired the company holding the Mining licenses over the long-abandoned Onganja copper mining operations. Years of surface exploration for new orebodies, resulted in the discovery of two feeder vein systems and their related mantos, carrying massive chalcopyrite ore. Underground development by way of an inclined shaft to reach the first discovered manto was completed. This was followed by the construction of a conventional crushing, milling and flotation ore beneficiation plant for the production of copper concentrate. At the time of writing, these accessory works are nearing completion.
Registration
Early Deadline: July 22, 2024
Regular Deadline: September 12, 2024
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| SEG Student and Recent Graduate Members |
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| Non-member |
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| All prices are in United States dollars (USD). SEG reserves the right to cancel this event should minimum attendance numbers not be met by July 22, 2024. All registrants will be given a full refund should SEG cancel the field trip. Cancellation policy, event photography, dietary restrictions, and more are detailed in the SEG Conference terms and conditions. |
All field trip registrants will be required to provide proof of emergency medical evacuation coverage in order to participate in conference field trips. Individuals may conveniently purchase this coverage online through various organizations such as International SOS or utilize existing coverage that they may already have through their employment. Further details and additional required documentation will be shared with registrants.
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