Open AccessRare elements — setting markers of the formation of the manganese and iron ore deposits of Kalahari and Postmasburg areas (South Africa). Communication 2. Iron- and manganese ore of Postmasburg area
Author(s) -
И.М. Варенцов,
И.М. Варенцов,
В. Н. Кулешов,
В. Н. Кулешов
Publication year - 2019
Publication title -
litologiâ i poleznye iskopaemye
Language(s) - English
Resource type - Journals
ISSN - 0024-497X
DOI - 10.31857/s0024-497x20195466-485
Subject(s) - manganese , geochemistry , geology , karst , banded iron formation , mineralogy , metallurgy , archean , materials science , paleontology
In the world resources of manganese and iron ores, a significant place belongs to the Postmasburg ore field (South Africa), enclosed in rocks of the Transvaal Supegroup. Ore deposits have the nature of karst residual accumulations. A number of elements (B, Cr, Ni, Zn, Ge, As, Se, Mo, Ag, Cd, Sb, Te, W, Pb, REE) form a characteristic association that sheds light on the geochemistry of the ore formation processes. Of these, the most representative elements are: Mo, As, Ag and REE. Molybdenum is distinguished by the chemisorption incorporation nature of accumulation in the ores under consideration, often with the formation of epic growths of ferri molybdate-type minerals. Arsenic leached from substrate rocks and accumulated in karstic Mn-Fe- and Fe-ores reflects the total effect of the dominant iron oxide minerals on its mobility. The behavior of silver is controlled by the processes of hypergenic change of Archean-Early Proterozoic carbonate rocks and banded iron ores (BIF). Comparison of the distribution of REE in karst Fe-, Mn-Fe- and Mn-ores and in banded iron ores shows that they are characterized by similar values of cerium (C/Ce*) and europium (Eu/Eu*) anomalies, but differ in the fractionation of heavy and light REE (typical values: Ce/Ce* = 0.7‒1.0; Eu/Eu* = 0.8‒1.1). Strip iron ores and associated manganese ore deposits accumulated in the marginal anoxide-disoxide marine basin, which was limited to continental land. Anoxide and disoxide conditions were the result of intense hydrothermal activity.