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The significance of manganese ores is very weil known in cast iron and steel production, as weil as in various types of chemical raw material and agricultural fertilizers. The world industry development in recent years requires their increased production in the vicinity of the metallurgical centers in different regions of the world; high grade manganese and associated metalores are needed. Analysis of the world production and consumption of manganese ores by industrial countries indicates convincingly that the highest commercial value belongs to the ores associated with the supergene zone (National Minerals Advi sory Board, 1981; Coffman and Palencia, 1984; Doncoisne, 1985; Iones, 1990, 1991; Manganese, 1990; McMichael, 1989). The remarkable property of manganese, in contrast to many other types of mineral resources, is that the ore accumulations of this metal are distributed in the wide geochrono logical interval from the Archean to the present time; these ores are deposited in basins and supergene environments of different types from lakes, internal seas to pelagic and abyssal regions of the World ocean, as weIl as different types of weathering crusts and karst. At the same time the manganese accumulations and features of their mineral and chemical compositions are relatively sensitive indicators, reflecting facies and geodynamic condi tions of their formation. These properties aid the investigation of the Earth's evolution processes.
Sommario
1. Introduction.- 2. Manganese Ores in Weathering Crusts.- 3. Manganese Ores in Karst.- 4. Model of Manganese Ore Formation in the Supergene Zone.- 5. Evolution of Manganese Ore Formation in the Earth's History.
Riassunto
The major part of the world's high grade industrial manganese ore is being mined in supergene deposits. This text represents an attempt to bring together not only academic but also commercial data on all aspects of the geochemistry of formation of supergene manganese ores.
