Influence of H2O and CO2 on deep melting beneath ridges

H2O和CO2对山脊下深层融化的影响

• 批准号: 0623550
• 负责人: Marc Hirschmann
• 金额: $ 33.88万
• 依托单位: University of Minnesota-Twin Cities
• 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: 2006-09-15 至 2011-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0623550&HistoricalAwards=false
• 关键词: Influence; H2O; CO2; deep; melting

ABSTRACT 0623550 (HIRSCHMANN)Intellectual Merit: This works determines the influence of H2O and CO2 on deep melting beneath ocean ridges, with consequent importance to sub-ridge rheology, dynamics, geochemistry, and observational geophysics, is well recognized. Questions addressed include: (1) at what depth does volatile-induced melting begin beneath mid-ocean ridges, and what proportions of melt are generated, (2) what the relationship between melting and dehydration beneath ridges is, and (3) what influence does CO2 have in inciting carbonated silicate partial melting and dehydration deep beneath ridges. Work will involve high pressure and temperature multi-anvil experiments to determine the influence of small amounts of H2O and CO2 on deep melting and dehydration. Experimental targets are the solidus of peridotite with small amounts of added H2O at 3, 4, and 5 Gpa; the extent of melting and the extent of residue dehydration of slightly hydrous peridotite at 3 Gpa; and the effect of CO2 on melting and residue dehydration of slightly hydrous peridotite at 3 and 4 GPa. Run products will be analyzed with electron microscopy, vibrational spectroscopy, and secondary ion mass spectrometry (SIMS). Special attention will be paid to SIMS analysis of H and H/Ce in nominally anhydrous minerals, providing direct evidence of mineral dehydration during partial melting as well as monitoring for potential H2O loss from experiments. The experimental results will provide strong constraints on the relationship between volatiles and melting beneath ridges that should prove useful to geochemists investigating the relationship between melting regime and the volume and composition of melts produced, to geophysicists characterizing melting and temperature anomalies beneath ridges, and to geodynamicists seeking to model the relationship between mantle flow, melting, and development of the oceanic lithosphere. Broader Impacts: The experimental results will be incorporated into the LEPER (Library of Experimental PhasE Relations) database of experimental mineral/melt phase equilibria presently being compiled by the PI and will provide key data of the MELTS algorithm for the effect of H2O and CO2 on mantle melting, for which available constraints are presently sparse. The proposed research will support a faculty member at the University of Minnesota, provide training for a graduate student, and will aid education of undergraduates. In particular, the research activities will be integrated into opportunities for undergraduate education through an NSF-funded REU site (Fluids in the Earth from Surface to Core) and will employ undergraduate research assistants.

摘要 0623550 (HIRSCHMANN) 学术价值：这项工作确定了 H2O 和 CO2 对洋脊下方深层融化的影响，从而对洋脊流变学、动力学、地球化学和观测地球物理学具有重要意义，这一点已得到广泛认可。 所讨论的问题包括：（1）挥发物引起的融化在洋中脊下方什么深度开始，以及产生的融化比例是多少；（2）洋中脊下方融化和脱水之间的关系是什么；（3）二氧化碳在引发洋中脊下方深处碳酸化硅酸盐部分熔融和脱水方面有什么影响。 工作将涉及高压和高温多砧实验，以确定少量的 H2O 和 CO2 对深度熔化和脱水的影响。 实验目标是在 3、4 和 5 Gpa 下添加少量 H2O 的橄榄岩固相线； 3 Gpa 下微含水橄榄岩的熔融程度和残渣脱水程度；以及 CO2 在 3 和 4 GPa 下对微水橄榄岩熔融和残渣脱水的影响。 运行产物将通过电子显微镜、振动光谱和二次离子质谱 (SIMS) 进行分析。 将特别关注名义上无水矿物中 H 和 H/Ce 的 SIMS 分析，提供部分熔融过程中矿物脱水的直接证据，并监测实验中潜在的 H2O 损失。 实验结果将为山脊下的挥发物和熔融之间的关系提供强有力的约束，这对于研究熔融状态与所产生的熔体的体积和成分之间的关​​系的地球化学家、描述山脊下的熔融和温度异常的地球物理学家以及寻求模拟地幔流、熔融和海洋岩石圈发育之间关系的地球动力学家来说都是有用的。 更广泛的影响：实验结果将被纳入PI目前正在编制的实验矿物/熔体相平衡的LEPER（实验相关系库）数据库，并将为H2O和CO2对地幔融化影响的MELTS算法提供关键数据，目前可用的约束条件很少。 拟议的研究将为明尼苏达大学的一名教职人员提供支持，为研究生提供培训，并帮助本科生的教育。 特别是，研究活动将通过 NSF 资助的 REU 站点（从地表到地核的地球流体）纳入本科教育机会，并将聘用本科生研究助理。