Influence of H2O and CO2 on deep melting beneath ridges

摘要0623550（HIRSCHMANN）学术价值：这项工作确定了H2O和CO2对洋脊下深层熔融的影响，从而对洋脊下流变学、动力学、地球化学和观测地球物理学具有重要意义，这是公认的。 讨论的问题包括：（1）在大洋中脊下，挥发物引起的熔融开始在什么深度，熔融的比例是多少，（2）洋脊下熔融和脱水之间的关系是什么，（3）CO2对激发洋脊下碳酸盐硅酸盐部分熔融和脱水有什么影响。 工作将涉及高压和高温多砧实验，以确定少量H2O和CO2对深熔和脱水的影响。 实验目标是橄榄岩的固相线与少量的添加H2O在3，4，和5 GPa;熔融的程度和程度的残余物脱水的轻度含水橄榄岩在3 GPa;和CO2的熔融和残余物脱水的轻度含水橄榄岩在3和4 GPa的效果。 将使用电子显微镜、振动光谱和二次离子质谱（西姆斯）分析运行产物。 将特别注意西姆斯分析名义上无水矿物中的H和H/Ce，提供矿物在部分熔融过程中脱水的直接证据，以及监测实验中潜在的H2O损失。 实验结果将提供强有力的限制挥发分和熔融脊下，应该被证明是有用的地球化学家调查熔融制度之间的关系和产生的熔体的体积和成分，熔融和温度异常脊下的特征，地球动力学家和地球动力学家寻求模拟地幔流动，熔融和发展之间的关系的关系的熔融制度。 更广泛的影响：实验结果将被纳入实验矿物/熔体相平衡数据库的LEPER（实验相位关系库）目前正在由PI编译，并将提供关键数据的MELTS算法的H2O和CO2对地幔熔融的影响，其中可用的约束是目前稀疏。 拟议的研究将支持明尼苏达大学的一名教员，为一名研究生提供培训，并将帮助本科生的教育。 特别是，研究活动将通过NSF资助的REU网站（地球表面到核心的流体）整合到本科教育的机会中，并将聘请本科研究助理。

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.