Abstract

Manganese ores of the Lower Proterozoic Hotazel Formation (Transvaal Supergroup) associated with the banded Fe-silicites are marked by high concentrations of several rare elements (B, Ge, W, Mo, Cr, Ni, Zn, Cd, Pb, Ag, Bi, As, Sb, Te, Se). High boron contents in the oxide‒carbonate ores (Mn-lutites) are attributed to the chemosorptional concentration of this element on Mn-carbonates. Owing to hydrothermal transformations, a wide range of the ore-forming (mainly Fe and Mn) and rare elements (REE included) was removed from the underlying hyaloclastic basaltic andesites of the Ongeluk Formation. Manganese ores and Fe-silicites are characterized by the typical values of the cerium (Ce/Ce* 0.28–1.72) and europium (Eu/Eu* 0.57–16.31) anomalies that can suggest that primary sediments were deposited in a marginal shallow-marine basin with a prominent oxic surficial water layer and subanoxic conditions near the floor. At different stages of lithogenesis, metalliferous (Mn, Fe) sediments of the shallow-water basin were enriched in Eu (positive Eu/Eu*) and subjected to metasomatism (with the redistribution of Mn and the formation of manganese carbonates) and the consequent regional metamorphism (up to the stage of green sericite schists).

中文翻译：

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稀有元素-卡拉哈里和波马斯堡油田（南非）中锰和铁矿床形成背景的标志：交流1.卡拉哈里锰田

摘要

与带状硅-硅酸盐岩相关的元古界下Hotazel​​组（Transvaal超群）的锰矿石具有高浓度的几种稀有元素（B，Ge，W，Mo，Cr，Ni，Zn，Cd，Pb，Ag，Bi ，As，Sb，Te，Se）。氧化物碳酸盐矿石（锰铝锰矿）中硼的含量高是由于该元素在锰碳酸盐上的化学吸附浓度所致。由于水热转变，从昂热鲁克组下伏的碎屑玄武质安山岩中除去了广泛的成矿作用（主要是铁和锰）和稀有元素（包括稀土元素）。锰矿石和铁硅铁矿的特征是铈（Ce / Ce * 0.28-1.72）和euro（Eu / Eu * 0.57-16）的典型值。31）异常现象，可能表明主要沉积物沉积在边缘浅海盆地中，该盆地具有明显的有氧表层水层和靠近底板的亚缺氧条件。在岩性形成的不同阶段，浅水盆地的含金属（Mn，Fe）沉积物中富集了Eu（正Eu / Eu *），并经历了交代作用（伴随Mn的重新分布和碳酸锰的形成），因此区域变质（直至绿色绢云母片岩阶段）。