Controls on the enrichment and transport of As and Sb in magmatic fluids: experimental studies and implications for hydrothermal Au-Ag-As-Sb deposits

岩浆液中砷和锑富集和运移的控制：热液金银砷锑矿床的实验研究和意义

• 批准号: 521731897
• 负责人: Professorin Dr. Carmen Sanchez-Valle, Ph.D.
• 金额: --
• 依托单位: Institut für Mineralogie
• 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/521731897?language=en
• 关键词: Controls; enrichment; transport; Sb; magmatic

The genesis of world-class magmatic-hydrothermal ore deposits is largely controlled by the efficient extraction of metals from a deep magma source and their transport by magmatic volatiles to superjacent environments. However, processes occurring at the so-called ‘magmatic-hydrothermal transition’, as magmas degas and crystallize, remain still poorly understood. Developing a robust quantitative understanding of these processes thus requires better constrains on the partitioning of metals between the magma source and the exsolved volatiles, and on the stability of metal complexes in the conveying magmatic volatile phase. Specifically, it is critical to quantify how changes in pressure, temperature, redox state and chemistry affect the partitioning and speciation of metals in ore-forming fluids. Yet, the experimental data is rather limited at magmatic-hydrothermal conditions ( 300-800 ⁰C, 0.5-3 kbar) due to exceptional experimental challenges associated to sampling unquenchable volatile phases. This proposal will address this gap of knowledge by applying a multidisciplinary experimental approach combining experimental and analytical work with thermodynamic modelling. We will particularly focus on the behaviour of As and Sb, and how they affect the mobility and transfer of precious metals Au-Ag, with whom they are associated in a large number of hydrothermal deposits. Volatiles (fluids) equilibrated with silicate melts will be probed by a combination of in situ synchrotron-based X-ray methods in a hydrothermal autoclave and ex situ fluid entrapment as synthetic fluid inclusions (SFI). Spectroscopic data acquired at P-T conditions relevant for the magmatic-hydrothermal transition, will identify the speciation of metals and allow thermodynamic description of the transfer of elements from the melt to the volatile phase. The obtained data will be employed to construct mass transfer and thermodynamic models to assess the role of granitic intrusions and exsolved volatiles as a source of As-Sb-Au-Ag metals in the formation of a range of hydrothermal ore deposits, from epithermal to Carlin-type Au/Ag-As-Sb deposits, at shallower depths.

世界级岩浆热液矿床的成因在很大程度上受控于金属从深源岩浆中的有效提取及其通过岩浆挥发分向超岩浆环境的迁移。然而，发生在所谓的“岩浆热液过渡”的过程，如岩浆脱气和结晶，仍然知之甚少。 因此，发展一个强大的定量了解这些过程需要更好地限制金属之间的岩浆源和出溶挥发物的分配，并在运送岩浆挥发相的金属络合物的稳定性。具体而言，它是至关重要的，以量化压力，温度，氧化还原状态和化学的变化如何影响成矿流体中的金属的分配和形态。然而，实验数据在岩浆热液条件下（300-800 ℃，0.5-3 kbar）相当有限，这是由于与采样不可淬灭的挥发性相相关的特殊实验挑战。该提案将通过采用多学科实验方法，将实验和分析工作与热力学建模相结合，来解决这一知识差距。我们将特别关注As和Sb的行为，以及它们如何影响贵金属Au-Ag的流动性和转移，它们在大量热液矿床中与贵金属Au-Ag相关。 与硅酸盐熔体平衡的挥发物（流体）将通过在热液高压釜中的原位同步辐射X射线方法和作为合成流体包裹体（SFI）的非原位流体圈闭相结合来探测。在P-T条件下获得的光谱数据与岩浆-热液过渡有关，将确定金属的形态，并允许从熔体到挥发相的元素转移的热力学描述。所获得的数据将用于构建质量转移和热力学模型，以评估花岗岩侵入体和出溶挥发物作为As-Sb-Au-Ag金属来源在浅部从浅成热液矿床到卡林型Au/Ag-As-Sb矿床等一系列热液矿床形成过程中的作用。