- Title
- Mineralogical and geochemical modification of manganese ore in response to fluid flow through the Hotazel Formation of the Kalahari Manganese Field, Northern Cape Province, South Africa
- Creator
- Vafeas, Nicholas Andrew
- Subject
- Geology - South Africa - Northern Cape, Mineralogical chemistry - South Africa - Northern Cape, Manganese ores - South Africa - Northern Cape
- Date
- 2018
- Type
- Doctoral (Thesis)
- Identifier
- http://hdl.handle.net/10210/292777
- Identifier
- uj:31822
- Description
- Abstract: The Kalahari Manganese Field hosts the largest land based manganese resource in the world, comprising several variants of manganese ore-types including diagenetic/Mamatwan-type, supergene, hydrothermal/Wessels-type and thrust-related manganese ore. The lower manganese ore bed of the Hotazel Formation from five mines was investigated and analysed petrographically. Four of the five mines were further analysed geochemically and include Mamatwan mine in the south of the lower Kalahari Manganese Field, Sebilo Manganese Resources and United Kalahari Manganese mine in the central lower Kalahari Manganese Field and Gloria mine in the north of the lower Kalahari Manganese Field. The lower manganese ore bed from these mines is structurally located below the N-S trending Blackridge Thrust Fault and comprises diagenetic, low-grade, high carbonate-bearing ore. The ore from Mamatwan mine bears the closest similarities to a proposed original protolith comprising abundant kutnohoritic and calcitic ovoidal concretions, ribbons and lenses that are variably distributed within a braunite I and kutnohorite matrix. The highest manganese content is found within the lower half of the lower manganese ore bed and exhibits a Mn2O3 content of 30-45 wt %. In the central part of the lower Kalahari Manganese Field, diagenetic ore is located at shallow depths just below the Kalahari unconformity and as a result is subjected to the effects of classic supergene alteration. These effects have resulted in the replacement of much of the diagenetic carbonate and oxides by supergene oxyhydroxides, including cryptomelane, psilomelane and pyrolusite. The development of these phases, coupled with the removal of carbonates has increased the manganese content to 40-55 wt %. In addition, the precipitation of classic supergene phases resulted in an increase in bulk chemical potassium and barium abundances within the ore, as well as the residual enrichment of vanadium. The manganese ore in the area of Mukulu is positioned above the Blackridge Thrust Fault and as such, has been displaced several tens of kilometres eastwards. The resultant ore exhibits signs of Wessels event alteration, reaching Mn2O3 abundances of 60-80 wt % and is significantly coarse-grained relative to the diagenetic ore. Three stages of alteration were identified in the Thrust Manganese ore i.e. Stages 1, 2 and 3, and closely resemble the..., Ph.D. (Geology)
- Contributor
- Viljoen, K.S.,Prof., Blignaut, L.C., Dr.
- Language
- English
- Rights
- University of Johannesburg
- Full Text
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