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.

研究火山，包括地球上形成火山的过程，是地球科学的重要组成部分。这种通常令人敬畏的地质过程经常扰乱航空公司航班等人类活动，有时还威胁到居住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一潜在致命现象的了解和理解。火山在破坏性板块边界(称为俯冲带)的弧形中发生的一个重要方面是，挥发性成分，如H2O和CO2，在高压和高温下岩石的原始熔融中发挥了作用。这种熔化过程形成了岩浆(熔岩和晶体混合物)，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融温度，决定产生的岩浆的物理性质(如密度和粘度)，并助长爆炸性喷发(气体膨胀)。这个项目的重点是这些挥发性成分对地幔融化过程的化学影响。从这个项目中获得的知识将有助于限制形成火山弧的岩浆的起源，它们最初的H2O和CO2含量，并将有助于我们全面了解火山的形成过程。这项实验研究将解决的特别问题是水对地幔条件下熔体的二氧化硅活动的影响。虽然已经在实验上观察到，在含水条件下形成的地幔熔体含有明显更高的二氧化硅含量，并且在显著较低的温度下熔融，但基本关系仍然不受实验数据的约束。作为对现有限制的补充，这项研究将使用一系列成分(从镁铁质到中间体)的实验来系统地测量P、T和可变流体(H2O-CO2)组成对二氧化硅活性的影响。由此得到的数据将使热力学分析能够显示可能与上地幔平衡的含水熔体的范围，从而澄清H2O在原始熔体生成中的作用(或缺乏作用)。