U.S.-Japan Cooperative Research: Study of Melt-Solid Segregation in the Upper Mantle as Represented by the Horoman Peridotite, Hokkaido, Japan

该奖项将促进麻省理工学院地球、大气和行星科学系Frederick A. Frey教授和Nobumichi Shimizu教授与日本熊本大学地质系Masaaki Obata教授以及几位日本同事之间在地球科学方面的合作。科学家们将合作研究霍罗曼橄榄岩，这是一种位于日本北海道岛的大型暴露火成岩。它是一个不寻常的地层，起源于地球的上地幔，具有发育良好的层状结构，矿物组成有系统的变化，岩石暴露良好，相对不受地壳蚀变的影响。这些性质使其成为研究上地幔中发生的某些地球化学过程，特别是部分熔体的形成、分离和迁移的理想材料。观测到的分层被解释为反映了部分熔融的上升地幔中的“岩浆波”。因此，霍罗曼实际上可能是一块上地幔，在那里，熔体形成和分离的过程被冻结在原地。合作的科学家将对橄榄岩的形成进行实地定量和岩石学研究，并对岩石中的主要和微量元素丰度和放射性成因同位素比率进行地球化学分析。对层状上地幔岩石的研究是重要的，因为它提供了有关地球上地幔发生的部分熔融和熔体分离的信息。尽管人们对这些过程知之甚少，但它们似乎是地球过去、现在和未来进化的基础。对霍罗曼橄榄岩的研究旨在更好地理解这些过程。

This award will facilitate cooperation in earth science between Professors Frederick A. Frey and Nobumichi Shimizu, Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, and Professor Masaaki Obata, Department of Geology, Kumamoto University, Japan, and several Japanese colleagues. The scientists will collaborate in a study of the Horoman peridotite, a large, exposed igneous rock formation on the Japanese island of Hokkaido. It is an unusual formation, derived from the earth's upper mantle, and characterized by a well developed layer structure, with systematic changes in mineral composition and well-exposed rocks which are relatively free from crustal alteration. These properties make it ideal for studying certain geochemical processes that have occurred in the upper mantle, particularly the formation, segregation and migration of partial melts. The observed layering has been interpreted as reflecting "magma waves" in a partially molten, ascending mantle. The Horoman may thus actually be a piece of upper mantle where the processes of melt formation and segregation have been frozen in situ. The cooperating scientists will combine a quantitative field and petrologic study of the peridotite formation with geochemical analyses for major and trace element abundances and radiogenic isotope ratios in the rocks. A study of layered upper mantle rocks is important because it provides information on the partial melting and melt segregation occurring in the earth's upper mantle. Though poorly understood, these processes appear to be fundamental to the past, current, and future evolution of the earth. This investigation of the Horoman peridotite is aimed at contributing to a better understanding of these processes.