Collaborative Research: The Behavior of Sulfur During Magma Mixing and Implications for Magma Degassing and Ore Formation

合作研究：岩浆混合过程中硫的行为及其对岩浆脱气和成矿的影响

• 批准号: 1707615
• 负责人: Philipp Ruprecht
• 金额: $ 3.41万
• 依托单位: Board of Regents, NSHE, obo University of Nevada, Reno
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-12-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1707615&HistoricalAwards=false
• 关键词: Collaborative; Research; Behavior; Sulfur; During

The proposed experimental study will elucidate the effect(s) of magma mixing on the mobility of sulfur and sulfur-affine elements. In particular, this study investigates the interaction of sulfur-rich magmas coming from the mantle that mix with more evolved magmas that are typically stored for extended times in magma chambers below the volcanic edifice and have relatively low sulfur concentrations. Understanding the behavior of sulfur during such mixing should significantly improve our ability to forecast volcanic behavior. In the atmosphere, volcanic-released sulfur (often during magma mixing) modulates climate and leads to acid rain in humid volcanic regions. Furthermore, sulfur mobility during magma mixing is thought to facilitate metal transport from silicate melt to magmatic aqueous fluids that are responsible for the evolution of societally important magmatic-hydrothermal ore deposits. A quantitative understanding of how sulfur is mobilized and how it facilitates mass transport during magma mixing of andesite and dacite magma remains unexplored experimentally. As magmas hybridize during diffusive re-equilibration, sulfur-bearing phase stability is investigated as a function of time and oxidation state. Given differential diffusivities of different components in diffusion-couple experiments, diffusive gradients lead to transient local environments, in which sulfides and/or sulfates may in one spot be precipitated while in another area they may be dissolved. This drives complex mass transfer between the mafic and felsic magma. Reduced and oxidized conditions will allow the team to assess the role of sulfur oxidation state on these processes.

建议的实验研究将阐明岩浆混合对硫和硫仿射元素的活动性的影响。特别是，本研究探讨了来自地幔的富硫岩浆的相互作用，这些岩浆与更演化的岩浆混合，这些岩浆通常在火山建筑物下方的岩浆房中储存较长时间，并且硫浓度相对较低。了解硫在这种混合过程中的行为，将大大提高我们预测火山活动的能力。在大气中，火山释放的硫（通常在岩浆混合过程中）调节气候，并导致潮湿火山地区的酸雨。此外，岩浆混合过程中硫的流动性被认为有助于金属从硅酸盐熔体向岩浆水流体的迁移，而岩浆水流体是岩浆热液矿床演化的重要原因。在安山岩和英安岩岩浆的岩浆混合过程中，硫是如何被动员起来的，以及硫是如何促进质量输送的，这些都还没有得到实验上的定量研究。作为岩浆杂交扩散再平衡过程中，含硫相的稳定性作为时间和氧化态的函数进行了研究。在扩散耦合实验中，由于不同组分的扩散系数不同，扩散梯度会导致局部环境的瞬态，其中硫化物和/或硫酸盐可能在一个点沉淀，而在另一个区域溶解。这驱动了镁铁质和长英质岩浆之间复杂的质量转移。还原和氧化条件将使研究小组能够评估硫氧化态对这些过程的作用。