Collaborative Research: Experimental Study of H, S, Cl, and F Partitioning Between Apatite, Fluid(s), and Melts: Applications to Magma Evolution and Volatile Component Exsolution

知识价值。挥发性组分水、碳、硫、氯、氟影响岩浆流变和分异，控制火山脱气和喷发过程，影响岩浆组分在流体中的溶解和运移，引起交代作用和热液成矿作用。火山岩浆挥发物的脱气也从根本上影响大气和海洋的地球化学，从而影响地球的气候。这些过程的功效与挥发物的丰度直接相关。尽管通过对火山和深部岩石中被困硅酸盐熔体包裹体和含水矿物的分析，以及互补的实验和理论研究，对岩浆挥发性成分进行了广泛的研究，但目前对挥发物的行为和丰度的了解还不足以准确模拟岩浆演化过程中的流体过程。特别是，我们必须更好地了解富含挥发物的岩浆流体何时首次溶解，它们的成分在岩浆演化过程中如何变化，以及这些流体如何积聚在岩浆房的顶端，以控制岩浆过程和火山活动。无处不在的矿物磷灰石[Ca5(PO4)3(OH，F,Cl)]含有氟、氯和羟基离子作为基本成分，还可能含有微量到主要元素水平的硫。如果我们有定量的元素分配知识，磷灰石可能被用来监测其形成的岩浆中的挥发性含量。拟议的调查旨在通过控制实验和在已知压力、温度和熔体成分下形成的运行产品的详细分析提供必要的校准信息。研究的最终目标是将磷灰石发展成为一种地球化学工具，用于：(1)估算熔体演化不同阶段的岩浆挥发物含量（并不总是以原生熔体包裹体的存在为代表）；(2)跟踪岩浆演化过程中挥发物组分的行为；(3)阐明岩浆流体在脱气和火山喷发过程中的作用；(4)改进能够预测这些交换过程并应用于自然系统的热力学模型。更广泛的影响。该项目可能会导致开发出评估岩浆挥发性成分的有力替代方法。科学成果及其与社会的相关性将传达给参加美国自然历史博物馆nsf支持的本科生研究经历（REU）项目的暑期实习生，并通过博物馆的讲座项目（重点是挥发物和地质过程）传达给教师和公众。博物馆提供了许多其他机会，通过电子媒体在展厅与公众分享科学研究成果。研究结果也将在马里兰大学的本科生培训中分享，并通过马里兰大学的地球科学开放日活动对公众进行教育。

Intellectual merit. The volatile components water, carbon, sulfur, chlorine, and fluorine affect magma rheology and differentiation, control processes of volcanic degassing and eruption, and influence the dissolution and transport of magmatic components in fluids that cause metasomatism and hydrothermal mineralization. The degassing of magmatic volatiles from volcanoes also fundamentally affects the geochemistry of the atmosphere and oceans - thus influencing Earth's climate. The efficacy of these processes varies directly with the abundances of volatiles. Despite extensive study of magmatic volatile components via analyses of trapped silicate melt inclusions and hydrous minerals in volcanic and plutonic rocks, and complementary experimental and theoretical research, current knowledge of the behavior and abundances of volatiles is insufficient for accurate modeling of fluid processes during magma evolution. In particular, we must better understand when volatile-rich magmatic fluids first exsolve, how their compositions change during magma evolution, and how these fluids accumulate in the apices of magma chambers to control magmatic processes and volcanic activities. The ubiquitous mineral apatite [Ca5(PO4)3(OH,F,Cl)] contains fluorine, chlorine, and hydroxyl ions as essential constituents and may also contain trace- to major-element levels of sulfur. If we have quantitative knowledge of element partitioning, apatite potentially can be used to monitor volatile contents in the magmas from which it forms. The proposed investigation aims to provide that essential calibration information via controlled experiments and detailed analysis of run products formed at known pressure, temperature, and melt composition. The ultimate goal is to develop apatite as a geochemical tool for: (1) estimating magmatic volatile contents at various stages of melt evolution (not always represented by presence of primary melt inclusions), (2) tracking the behavior of volatile components during progressive magma evolution, (3) elucidating the role of magmatic fluids in processes of degassing and volcanic eruption, and (4) improving thermodynamic models that can predict these exchange processes and apply to natural systems.Broader Impacts. This project will likely result in development of powerful alternative methods for assessing magmatic volatile contents. The scientific results and their relevance to society will be conveyed to summer interns participating in an NSF-supported Research Experiences for Undergraduate students (REU) program at the American Museum of Natural History, and to teachers and the generall public via a lecture program (focused on volatiles and geologic processes) at the museum. The museum offers numerous other opportunities to share the results of scientific research with the public through electronic media in exhibition halls. The results will also be shared by training undergraduate students at the University of Maryland and by educating the public through an open-house event on Earth science at the University of Maryland.