Defining the Hydrous Petrogenetic Grid: Experimental Constraints on Primitive Hydrous Magmas

定义含水成岩网格：原始含水岩浆的实验约束

• 批准号: 0610005
• 负责人: Gordon Moore
• 金额: $ 30.05万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-01 至 2010-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0610005&HistoricalAwards=false
• 关键词: Defining; Hydrous; Petrogenetic; Grid; Experimental

The study of volcanoes, including the processes in the earth that give rise to them, is an important part of earth sciences. This often awe-inspiring geologic process often disrupts human activity such as airline flights, and sometimes threatens the lives of the millions of people that live near volcanic centers. Therefore, there is much at stake that depends on our knowledge and understanding of this potentially deadly phenomenon. One important aspect of volcanoes that occur in arcs at destructive plate boundaries (known as subduction zones) is the role that volatile components such as H2O and CO2 play in the original melting of rock at high pressure and temperature. This melting process forms the magmas (molten rock and crystal mixtures) that are eventually erupted at the surface as lavas. It is well known that H2O and CO2 influence the initial melting temperature of the source rocks of volcanoes, determine the physical properties of the resulting magma (such as its density and viscosity), and fuel explosive eruptions (gas expansion). This project is focused on the influence of these volatile components on the chemistry of the melting process in the Earth's mantle. The knowledge gleaned from this project will help constrain the origins of the magmas that form volcanic arcs, their initial H2O and CO2 contents, and will contribute to our overall understanding of the processes that create volcanoes.The particular question that will be addressed by this experimental study is the influence of H2O on the silica activity of melts at mantle conditions. While it has been experimentally observed that mantle melts formed under hydrous conditions contain significantly higher silica contents, and melt at significantly lower temperatures, the fundamental relationships remain poorly constrained by experimental data. As a complement to existing constraints, this study will use experiments over a range of compositions (mafic to intermediate) to systematically measure how P, T, and variable fluid (H2O-CO2) composition influence the silica activity. The resulting data will enable a thermodynamic analysis showing the range of hydrous melts that could have been in equilibrium with the upper mantle, and thus will clarify the role (or the lack thereof) of H2O in the generation of primitive melts.

对火山的研究，包括地球上火山形成的过程，是地球科学的重要组成部分。这种令人惊叹的地质过程经常扰乱人类活动，例如航空航班，有时甚至威胁到生活在火山中心附近的数百万人的生命。因此，这在很大程度上取决于我们对这种潜在致命现象的了解和理解。破坏性板块边界（称为俯冲带）弧形火山发生的一个重要方面是，H2O 和 CO2 等挥发性成分在高压和高温下的岩石原始熔化中所起的作用。这种熔化过程形成岩浆（熔融岩石和晶体混合物），最终以熔岩的形式在地表喷发。众所周知，H2O和CO2影响火山源岩的初始熔化温度，决定所产生的岩浆的物理性质（例如其密度和粘度），并为爆炸性喷发（气体膨胀）提供燃料。该项目的重点是这些挥发性成分对地幔熔化过程化学的影响。从这个项目中收集到的知识将有助于确定形成火山弧的岩浆的起源、它们最初的H2O和CO2含量，并将有助于我们对火山形成过程的整体理解。这项实验研究将解决的具体问题是H2O对地幔条件下熔体二氧化硅活性的影响。虽然实验观察到在含水条件下形成的地幔熔体含有显着较高的二氧化硅含量，并且在显着较低的温度下熔化，但基本关系仍然很少受到实验数据的约束。作为对现有限制的补充，本研究将使用一系列成分（镁铁质到中间质）的实验来系统地测量 P、T 和可变流体 (H2O-CO2) 成分如何影响二氧化硅活性。由此产生的数据将能够进行热力学分析，显示可能与上地幔处于平衡状态的含水熔体的范围，从而阐明水在原始熔体生成中的作用（或缺乏水）。