Collaborative Research: An Experimental and Analytical Investigation of the Parameters That Influence Measured CO2 in Plagioclase-Hosted Melt Inclusions in MORB

合作研究：对影响 MORB 斜长石熔体包裹体中 CO2 测量值的参数进行实验和分析研究

• 批准号: 1634206
• 负责人: Frank Tepley
• 金额: $ 29.95万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1634206&HistoricalAwards=false
• 关键词: Collaborative; Research; Experimental; Analytical; Investigation

Volcanoes are major Earth features and, when they erupt, can cause significant damage to life, infrastructure, and ecosystems. When they occur on the seafloor, they can also trigger tsunamis that have the potential to cause devastating damage to coastal communities. Thus, our understanding of magmatic processes is important for both understanding how the Earth works as well as for helping us understand the dangers magmatic events and volcanic eruptions can cause. This research focuses on the story about magmatic processes that occur deep in the Earth as told by tiny inclusions of melt trapped in crystals of plagioclase, one of the most ubiquitous minerals in the Earth's crust. Up until now, melt inclusions in plagioclase have not been considered reliable archives of primary information for volatile geochemical species like H2O, CO2, or S due to diffusion and post entrapment leakage. There have also been questions about the origin of melt inclusions and when and where they form in the history of the plagioclase in which they occur. This research combines innovative laboratory experiments and comprehensive controlled calibration studies to reconstruct the original volatile composition of melt inclusions in plagioclase from ultra-phyric lavas erupted on the seafloor in the Pacific Ocean on the Juan de Fuca Ridge, just west of the Washington and Canadian border. The experiments will be done on both plagioclase and coexisting olivines from the same suite of samples to compare against one another and assess the degree to which post entrapment crystallization and the process of reheating impact the measured volatile content of the inclusions. Time-series experiments will be conducted on a heating stage at various temperatures (from 1200 C to 1270 C) and heating rates. Analyses of the major element composition of the inclusions will be carried out via electron microprobe; trace element compositions will be determined using laser inductively coupled mass spectrometry; Fourier transform infrared spectroscopy will be used to verify CO2 and H2O compositions of large inclusions; and the ion microprobe and micro-Raman spectroscopy will be used to analyze CO2, H2O, S, and Mg. The proposed experiments that will be carried out will determine the mechanisms by which volatiles are lost from inclusions during transport in the crust or during experimental heating via process such as diffusion, formation of bubbles, and leakage through cracks in the crystal. Goals of the research are to produce better measurements of the depth of mineral crystallization from magmas in mid-ocean ridge environments for both olivine and plagioclase. Questions to be addressed include how post entrapment crystallization in the inclusion and the formation of bubbles affect the measured volatile contents of the melt inclusions; how different homogenization methodologies and quench rates influence measured volatile contents; what the measured values of different volatile species indicate about the depth of formation of the crystal cargo and the CO2 budget of the ocean crust; and how does the information from plagioclase melt inclusions compare to that coming from olivine melt inclusions. Broader impacts of the work include development of new experimental techniques that have potential implications to other fields, societal impacts in terms of better understanding volcanic processes and understanding magmatically generated ore deposits. It will also involve the training of two graduate students and two undergraduates.

火山是地球的主要特征，当它们爆发时，会对生命、基础设施和生态系统造成重大损害。 当它们发生在海底时，它们还会引发海啸，有可能对沿海社区造成毁灭性破坏。 因此，我们对岩浆过程的了解对于了解地球如何运作以及帮助我​​们了解岩浆事件和火山喷发可能造成的危险都很重要。这项研究的重点是地球深处发生的岩浆过程，斜长石晶体中的微小熔体夹杂物讲述了岩浆过程，斜长石是地壳中最普遍的矿物之一。 到目前为止，由于扩散和截留后泄漏，斜长石中的熔体包裹体尚未被认为是挥发性地球化学物质（如 H2O、CO2 或 S）主要信息的可靠档案。 关于熔体包裹体的起源以及它们在斜长石历史上形成的时间和地点也存在疑问。 这项研究结合了创新的实验室实验和全面的受控校准研究，重建了斜长石熔体包裹体的原始挥发性成分，这些熔岩来自于华盛顿和加拿大边境以西的胡安德富卡海岭海底喷发的超火熔岩。 。 实验将对来自同一组样品的斜长石和共存橄榄石进行，以相互比较并评估包埋后结晶和再加热过程对测量的内含物挥发性含量的影响程度。时间序列实验将在不同温度（1200℃至1270℃）和加热速率的加热台上进行。 通过电子探针对包裹体的主要元素成分进行分析；将使用激光感应耦合质谱法测定微量元素成分；傅里叶变换红外光谱将用于验证大包裹体的CO2和H2O成分；离子微探针和微拉曼光谱将用于分析CO2、H2O、S和Mg。 即将进行的实验将确定挥发物在地壳运输过程中或在实验加热过程中通过扩散、气泡形成和通过晶体裂缝泄漏等过程从夹杂物中损失的机制。该研究的目标是更好地测量洋中脊环境中岩浆中橄榄石和斜长石的矿物结晶深度。 需要解决的问题包括夹杂物中的包埋后结晶和气泡的形成如何影响熔体夹杂物的挥发物含量的测量；不同的均化方法和淬火速率如何影响测量的挥发物含量；不同挥发性物质的测量值表明了晶体货物的形成深度和洋壳的二氧化碳收支；斜长石熔融包裹体的信息与橄榄石熔融包裹体的信息相比如何。这项工作的更广泛影响包括开发对其他领域具有潜在影响的新实验技术，以及更好地了解火山过程和了解岩浆生成的矿床方面的社会影响。它还将涉及两名研究生和两名本科生的培训。

项目成果

CO2 and H2O in Plagioclase-Hosted Melt Inclusions from Ocean-Ridge Lavas: An Indicator of Crystallization in the Lower Oceanic Crust

来自洋脊熔岩的斜长石熔体包裹体中的 CO2 和 H2O：下洋地壳结晶的指标

• 发表时间: 2019
• 期刊: abstract #V13C-0172
• 作者: • Kotash, A.;• Tepley, F. J.;• Nielsen, R.;• Bodnar, R. J.
• 通讯作者: • Bodnar, R. J.

Upper mantle origin of plagioclase megacrysts from plagioclase-ultraphyric mid-oceanic ridge basalt

• DOI: 10.1130/g45542.1
• 发表时间: 2018-11
• 期刊: Geology
• 影响因子: 5.8
• 作者: M. Drignon;R. Nielsen;F. Tepley;R. Bodnar

Experimentally Induced Volumetric Re‐equilibration of Plagioclase‐Hosted Melt Inclusions

实验诱导斜长石的体积重新平衡——托管熔体包裹体

• DOI: 10.1029/2020gc009357
• 发表时间: 2021
• 期刊: Geosystems
• 作者: Drignon, Mélissa J.;Arbaret, Laurent;Cluzel, Nicolas;Nielsen, Roger L.;Bodnar, Robert J.
• 通讯作者: Bodnar, Robert J.