Potential role of alkaline aqueous fluids in the formation of supergene and low-temperature hydrothermal mineralizations: experiments and natural analogues

碱性水流体在表生和低温热液矿化形成中的潜在作用：实验和天然类似物

• 批准号: 441301783
• 负责人: Professor Dr. Michael Bau
• 金额: --
• 依托单位: Department of Physics and Earth Sciences
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/441301783?language=en
• 关键词: Potential; role; alkaline; aqueous; fluids

The significance of hot, acidic fluids for the formation of ore deposits, especially in hydrothermal settings, is reasonably well understood. Such fluids are widely recognized as the most important transport media for metals and other solutes in most hydrothermal systems.In contrast, the role of alkaline fluids wth pH >>7, in ore formation is, with few exceptions, only poorly constrained. This is due to the fact that not only are many geochemical parameters and the behavior of critical metals in such fluids not known, but that for many elements even most basic information such as concentration data for natural alkaline waters, are simply not available. This severe knowledge gap prevents any reliable assessment of their potential role during the formation of ore deposits. Alkaline fluids, however, are ubiquitous and occur in many geological settings ranging from endorheic lakes to groundwater to marine hydrothermal fluids. Such fluids could have contributed to the formation of supergene and low-temperature hydrothermal deposits. Here, we intend to constrain the potential contribution of alkaline fluids to the formation of ore deposits by identifying geochemical and isotopic fingerprints of high field strength elements in alkaline solutions and in rocks that have interacted with high-pH solutions. To reach this goal, we will first investigate the distribution of HFSE (e.g., rare earth elements and Y, Sc, Zr, Hf, Nb and Ta) and the isotopic composition of Sr and Nd in alkaline lakes in Europe (e.g., Austria, Hungary), East-Africa, and the US. After having characterized the major, minor and trace solute geochemistry and further important physico-chemical parameters, untreated aliquots of these solutions are used for leaching experiments with a range of different rocks and with potential protores. These experiments will be complemented by experiments using artificial solutions that mimic simplified natural ones. The mobility of HFSE and their isotopes during water-rock interaction in alkaline conditions is not well constrained. This project will, close a significant knowledge gap by providing, for the first time, a comprehensive database of the HFSE and isotope distribution in alkaline waters from several locations. It will provide important information on how such alkaline fluids interact with rocks and how they affect the mobility of critical elements during water-rock interaction. The geochemical signatures in the leachates and the solid residues may be utilized as fingerprints of the involvement of alkaline fluids and will help geochemists and economic geologists alike to assess whether such fluids contributed to the formation of supergene and low-T hydrothermal ore deposits. This study will be complemented by geochemical modeling and finally, a comparison to geochemical data from actual ore deposits, in which the potential contributions of alkaline fluids to the formation of the described deposits will be investigated.

热酸性流体对矿床形成的重要性，特别是在热液环境中，已相当清楚。在大多数热液系统中，这种流体被广泛认为是金属和其他溶质最重要的输运介质。相比之下，除了少数例外，pH值为> bbb7的碱性流体在成矿中的作用受到的约束很差。这不仅是因为许多地球化学参数和这些流体中关键金属的行为不为人所知，而且对于许多元素，甚至连最基本的信息，如天然碱性水的浓度数据，也根本无法获得。这种严重的知识差距妨碍了对它们在矿床形成过程中的潜在作用进行可靠的评估。然而，碱性流体无处不在，并且出现在许多地质环境中，从内陆湖到地下水到海洋热液流体。这些流体可能促成了表生和低温热液矿床的形成。在这里，我们打算通过在碱性溶液和与高ph溶液相互作用的岩石中识别高场强元素的地球化学和同位素指纹，来限制碱性流体对矿床形成的潜在贡献。为了实现这一目标，我们将首先研究欧洲（如奥地利、匈牙利）、东非和美国碱性湖泊中HFSE（如稀土元素和Y、Sc、Zr、Hf、Nb和Ta）的分布以及Sr和Nd的同位素组成。在描述了主要、次要和微量溶质的地球化学特征以及进一步重要的物理化学参数后，将这些溶液的未处理等分液用于一系列不同岩石和潜在原岩的浸出实验。这些实验将辅以模拟简化自然溶液的人工溶液实验。在碱性条件下，水-岩相互作用过程中HFSE及其同位素的迁移率没有得到很好的约束。该项目将通过首次提供来自几个地点的碱性水的HFSE和同位素分布的综合数据库，缩小重大的知识差距。它将提供有关此类碱性流体如何与岩石相互作用以及它们如何影响水岩相互作用过程中关键元素的流动性的重要信息。渗滤液和固体残留物中的地球化学特征可以作为碱性流体参与的指纹，有助于地球化学家和经济地质学家评估这些流体是否有助于表生矿床和低t热液矿床的形成。这项研究将辅以地球化学模拟，最后与实际矿床的地球化学数据进行比较，其中将调查碱性流体对所述矿床形成的潜在贡献。