Chemical and physical properties of magmatic sulfides and sulfide liquids at conditions of Earth’s deep upper mantle

地球上地幔深处岩浆硫化物和硫化物液体的化学和物理性质

• 批准号: 451014777
• 负责人: Dr. Christopher Beyer
• 金额: --
• 依托单位: Institut für Geologie, Mineralogie und Geophysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/451014777?language=en
• 关键词: Chemical; physical; properties; magmatic; sulfides

Base metal sulfides (Fe-Ni-Cu-S +/- Co, and Zn) and sulfide melts are ubiquitous accessory phases in basalts, peridotites, and mantle xenoliths, and are the most frequent inclusions in diamonds. Due to their nature, they are a sink for highly siderophile elements (HSE) and economically important chalcophile elements like platin-group elements, Cu, Zn, Ag, and Pb. The abundances of HSE in planetary materials are commonly used to track the evolution of planetary reservoirs and core formation, which in conjunction with information of the Re-Os radioactive decay systems, provides us with insights into the chronology of planetary-scale processes. Fe-Ni-Cu-S inclusions are overabundant in diamonds and suggests that a genetic link between sulfides and diamonds exists. We plan to investigate compositions that resemble natural inclusions recovered from lithospheric and sublithospheric diamonds more closely, i.e. compositions with a distinct eclogitic and peridotitic metal to S and Fe to Ni ratio. To complement existing experimental data, carried out at shallow mantle conditions, we will conduct high-pressure/high-temperature experiments at deep mantle conditions (i.e. below 200 km depths to the base of the upper mantle) in equilibrium with different silicates/oxides (olivine, wadsleyite, ringwoodite, majorite, and stishovite) to unravel the conditions of sulfide saturation and their effect on element partitioning between sulfides, sulfide melts, and silicates.Sulfide melts have distinctly different physical properties (e.g. density, viscosity, electrical conductivity) compared to silicates and silicate melts. If sulfide melts develop an interconnected network, which depends on the solid-solid and solid-melt interfacial energies between sulfide melts and coexisting silicates, as well as oxygen and sulfur fugacity, they will significantly contribute to the transport of siderophile and chalcophile elements, as well as the likelihood of efficient metal segregation during planetary core formation. Moreover, sulfide melts can dissolve significant amounts of C and play a key role in the genesis of large diamonds. We will determine the dihedral angle of sulfide melts coexisting with high-pressure mantle phases to identify the conditions under which sulfide melts are mobile in the deep mantle. Moreover, we will address the solubility of C and the precipitation of diamonds from sulfide melts at pressures that represent Earth’s transition zone.

贱金属硫化物（Fe-Ni-Cu-S +/- Co和Zn）和硫化物熔体是玄武岩、橄榄岩和地幔捕虏体中普遍存在的副相，也是金刚石中最常见的包裹体。由于它们的性质，它们是高度亲铁元素（HSE）和经济上重要的亲铜元素如铂族元素、Cu、Zn、Ag和Pb的汇。HSE在行星材料中的丰度通常用于跟踪行星储层和核心形成的演化，这与Re-Os放射性衰变系统的信息相结合，为我们提供了对行星尺度过程年表的见解。Fe-Ni-Cu-S包裹体在金刚石中含量丰富，表明硫化物与金刚石之间存在成因联系。我们计划调查的组合物，类似于从岩石圈和亚岩石圈金刚石回收天然夹杂物更密切，即组合物具有独特的榴辉岩和橄榄岩金属的S和Fe的Ni比。为了补充在浅地幔条件下进行的现有实验数据，我们将在深地幔条件下进行高压/高温实验（即200公里深度以下至上地幔底部）与不同的硅酸盐/氧化物平衡（橄榄石，wadsleyite，ringwoodite，majalite和stishovite），以揭示硫化物饱和的条件及其对硫化物之间元素分配的影响，硫化物熔体与硅酸盐和硅酸盐熔体相比具有明显不同的物理性质（例如密度、粘度、电导率）。如果硫化物熔体形成一个相互连接的网络，这取决于硫化物熔体和共存硅酸盐之间的固-固和固-熔体界面能，以及氧和硫的逸度，它们将显着有助于亲铁和亲铜元素的运输，以及行星核心形成期间有效金属分离的可能性。此外，硫化物熔体可以溶解大量的C，并在大型金刚石的成因中发挥关键作用。我们将确定硫化物熔体与高压地幔相共存的二面角，以确定硫化物熔体在深部地幔中移动的条件。此外，我们将解决C的溶解度和沉淀的钻石从硫化物熔体在压力下，代表地球的过渡区。