Provenance and genesis of the auriferous palaeoplacer deposits in the Palaeoproterozoic Moeda Formation, Minas Gerais, Brazil

巴西米纳斯吉拉斯的QuadriláTero FerríFero的古元古代Moeda组由若干砾岩/石英岩单元组成，在某些砾岩层中具有经济的金品位。这些矿床与世界其他地方的古砂矿有很大的相似之处，在世界其他地方，它们以其巨大的黄金和铀的经济潜力而闻名。最好的例子是南非著名的太古宙维特沃特斯兰德盆地，该盆地蕴藏着世界上约40%的已知可开采金矿。未来的任何探索的成功总是取决于一个健全的遗传模型。因此，该项目的目标是利用现代分析技术和应用现有的威特沃特斯兰德金矿的经验，重建莫伊达组金矿的成因。要解决的主要问题是，金最初是否以类似于威特沃特斯兰德矿床的碎屑颗粒进入容矿砾岩，如果是这样，碎屑金的来源(S)位于哪里，以及金在多大程度上被沉积后变质/热液重新活化。为此，计划进行地质实地考察、岩石学和岩石地球化学分析、多种硫同位素研究以及金、精选硫化物和硅酸盐的微量元素分析。此外，还将对毗邻的里约热内卢达斯维尔哈斯绿岩带中的金矿进行比较研究，因为它们似乎是最接近莫伊达建造砾岩中碎屑硫化物和金矿颗粒来源(S)的金矿。总体而言，预期结果将大大有助于我们更好地了解世界各地这种经济上最重要的砾岩赋存的金(和铀)矿床。

The Palaeoproterozoic Moeda Formation of the Quadrilátero Ferrífero in Minas Gerais (Brazil) consists of several conglomerate/quartzite units with economic gold grades in some conglomerate beds. These deposits bear strong similarities to palaeoplacer deposits elsewhere in the world where they are known for their enormous economic potential for both gold and uranium. The prime example is the famous Archaean Witwatersrand Basin in South Africa, which hosts about 40% of all known minable gold in the world. The success of any future exploration is invariably dependent on a sound genetic model. The goal of this project is, therefore, to reconstruct the genesis of the gold deposits in the Moeda Formation using modern analytical techniques and applying existing experience with the Witwatersrand deposits. The principal questions to be addressed are whether the gold came into the host conglomerate originally as detrital particles ¿ analogous to the Witwatersrand deposits ¿ and, if that was the case, where the source(s) of that detrital gold was (were) located, and moreover to which extent gold was (re-)mobilised by post-depositional metamorphic/hydrothermal fluids. To this effect geological fieldwork, petrological and lithogeochemical analyses, multiple sulphur isotope studies and trace element analyses of gold, selected sulphides and silicates are planned. This will be complemented by a comparative study on the gold deposits in the adjacent Rio das Velhas Greenstone Belt because they appear to be the closest equivalents to likely source(s) of the detrital sulphide and gold particles in the Moeda Formation conglomerates. Overall the expected results will help considerably in improving our understanding of this economically most important type of conglomerate-hosted gold (and uranium) deposits worldwide.