Manganese Ores in Weathering Crusts

Abstract

Among various types of manganese ores the largest accumulations of rich varieties occur in the supergene settings, in particular in laterite weathering crusts. This established empirical fact underlines the justice of the statement, made by V.I. Vernadskii in the beginning of the century that the highest concentrations of manganese were observed in the zone of free oxygen (Vernadskii, 1954a, 1954b). However, many classifications of manganese deposits do not sufficiently reflect the real diversity of genetic types of ores in the supergene zone (Berner, 1981; Betekhtin, 1946; Park, 1956; Roy, 1968, 1969, 1981; Strakhov et al., 1968; Varentsov, 1962; Varentsov and Rakhmanov, 1974). The general scheme by Patterson (1971), used by Banerdji (1981) fora number of minerals, associated with weathering, is devoid of similar drawbacks. It should be stressed that in our work this classification is somewhat modified in order to reflect more adequately the distinguishing features of manganese ores, formed as the result of supergene processes: 1. Deposits associated with laterites and saprolites. For example, deposits of manganese ores in humid tropical zones. 2. Manganese ores of the oxidation zone or secondary enriched ore deposits. This type includes the oxidized manganese associations, widely developed in the largest sedimentary-diagenetic, hydrothermal-sedimentary ore accumulations. For example, in the South Ukrainian and Georgian Oligocene basins, and the Late Devonian oxidized-carbonate ores of the Central Kazakhstan, etc. 3. Manganese deposits associated with supergene processes of leaching, infiltration, and redeposition. The scales of their ore content may vary sharply. For example, the largest accumulations in karst caves of the Postmasburg area, South Africa (reserves: hundreds min t of Mn) and relatively large ledges in deposits of Porozhinskoe (Eniseiskii ridge), Urkut (Bakoni Mountains, Hungary), Burshtynskoe (Western Ukraine) etc.