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首页> 外文期刊>South African Journal of Geology: Being the Transaction of the Geological Society of South African: Syndie die Verhandelinge van die Geologiese Vereniging van Suid-Afrika >Gold on the Kaapvaal Craton,outside the Witwatersrand Basin,South Africa
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Gold on the Kaapvaal Craton,outside the Witwatersrand Basin,South Africa

机译：在Kaapvaal Craton上，在Witvatersrand Basin，南非外

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摘要

Gold occurs in a variety of ancient geological environments in South Africa, the most well-known being the unique Witwatersrand Basin in the central part of the Kaapvaal Craton. Outside of the Witwatersrand Basin significant quantities of gold have been recovered from Archaean greenstone belts of the 3500 to 2700 Ma Kaapvaal Craton as well as from various occurrences in the 2600 to 2200 Ma Transvaal Supergroup. Very little gold has been found in younger formations. Archaean greenstone belts in South Africa are characterised by substantial sequences of ultramafic (komatiitic) volcanic rocks generally overlain by mafic volcanic successions which, in turn, are overlain in some cases by greywacke-shale sequences and younger arenaceous lithologies. Highly sheared and carbonate altered ultramafic zones, together with the immediately surrounding country rock, host some of the most important gold deposits on the Kaapvaal Craton. In the northern part of the Barberton Greenstone Belt, shearing tends to be most intense along the contact of the ultramafic schists of the Zwartkoppie Formation and the overlying greywacke-shales, the contact being marked by the presence of a chert "bar" or banded iron formation (BIF) horizon. Gold mineralisation occurs below, above and/or within the more competent and fractured chert/BIF marker horizon. The locus of gold mineralisation is typically controlled by the rheological characteristics of the wallrocks in the proximity of the shear systems, e.g. the ductile greywacke-shale strata are tightly folded with sub-parallel mineralised shear zones, while competent arenaceous rocks have yielded in a brittle manner resulting in high-angle mineralised fractures. Extensive carbonate alteration in ultramafic rocks is often present along, and in the vicinity of, shear zones where potassium alteration results in a vivid green coloration due to the formation of fuchsite (Cr-mica) and where zones of silicification and quartz veining are closely associated
机译：黄金发生在南非的各种古代地质环境中，最着名的是Kaapvaal Craton的中央部分独特的Witwatersrand盆地。在Witwatersrand Basin的外面，来自3500至2700 ma Kaapvaal Craton的大型青斯通带，从2600到2200 mA Transvaal Superroup的各种事件中恢复了大量黄金。在较年轻的地层中发现了很少的黄金。南非的考古青石带的特征在于大量超空白（Komatiitic）火山岩的序列通常由MAFIC火山继承的覆盖，反过来又在某些情况下覆盖在某些情况下，通过Greywacke - 页岩序列和年轻的植物岩性。高度剪切和碳酸盐改变了超空地，与立即周围的乡村岩石一起，举办了kaapvaal craton上最重要的金矿床。在Barberton Greenstone Belt的北部，剪切倾向于沿着Zwartkoppie的Quartramic Sc​​hist的接触和覆盖的Greywacke-Shales的接触，通过燧石“酒吧”或带状铁的存在标记的接触形成（BIF）地平线。在更有态度和/或更符合胜率和骨折的Chert / BIF标记范围内发生的金矿化发生。金矿化轨迹通常由钢管在剪切系统附近的船体的流变特性来控制，例如，控制。延展性灰色瓦尔斯 - 页岩地层与亚平行矿化剪切区紧密折叠，而具有脆性的岩石的胜利岩石产生高角度矿化骨折。超大碳酸盐岩的变化通常存在，并且在剪切区附近存在，其中钾改变导致由于紫陶（Cr-MIDA）的形成，并且硅化区和石英纱的区域密切相关

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