Manganese genesis, analysis and future demand: a case study from the United Manganese of Kalahari (UMK), Hotazel, South Africa

Abstract

The origin of the biggest manganese deposit in the world has been extensively researched and discussed for years with no consensus on the origin, due to its complex mineral associations. The Kalahari manganese field occurs within the 2.5G a Proterozoic Transvaal Supergroup, it is restricted to the Hotazel Formation of the Postmasburg Group in the Griqualand West basin and is at least 1100km2 in extent. The Kalahari Formation, comprising sand, calcrete, clay and pebble beds covers the ore-bearing Hotazel Formation, while the Mooidraai Formation, comprising dolomites locally underlies the Kalahari Formation. The ore bearing Hotazel Formation is composed of alternating layers of banded iron formations and braunite lutites. The difference in mineral distribution and ore composition has given rise to three types of ore; the slightly altered Mamatwan-type low-grade,the hydrothermally altered Wessels-type high-grade ore and the supergene enriched ore. The predominant minerals of the Kalahari basin are bixbyite, braunite, cryptomelane, hausmannite, jacobsite ,kutnahorite and todorokite. United Manganese of Kalahari mine extracts the economic lower ore body, that has an average of 20m in thickness. The mine hosts two types of manganese ore; the low-grade mamatwan-type and the supergene altered ore. The chemical composition of these types of manganese ore is determined using different analytical methods, titration and X-ray fluorescence are the most suitable for analysing oxides. In most cases, however, these methods have given quite significant differences of up to 2.5% in manganese content. As 2.5% manganese is a significant amount, re-analysis is required. Due to the globally competitive market, manganese ore is directly impacted by the demand in the steel industry. The amount of manganese used in the steel industry per quantity of steel produced has declined over time, due to improvements in technology since the 1950s. However, the worldwide increase in demand for steel will increase the demand for manganese. With the imminent 4th industrial revolution, the future for demand of manganese ore will be impacted. This research supports some of the previous studies on the genesis of manganese, with regard to a sedimentary origin and addressing the question of differences in assay values of the above mentioned analytical methods. The study ultimately looks into the economics of manganese, with focus on the future demand