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学系Masaaki Obata教授和几位日本同事在地球科学方面的合作。科学家们将合作研究荷罗曼橄榄岩，这是一种位于日本北海道的大型裸露火成岩建造。它是一种来自地球上地幔的不同寻常的建造，具有发育良好的层状结构，矿物成分有系统的变化，出露的岩石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、分离和迁移的理想工具。观察到的分层被解释为在部分熔融的上升地幔中反射“岩浆波”。因此，霍罗曼可能实际上是一块上地幔，熔体形成和分离的过程在原地冻结。合作的科学家将结合橄榄岩建造的定量现场和岩石学研究，以及岩石中主要和微量元素丰度和放射性同位素比率的地球化学分析。对层状上地幔岩石的研究很重要，因为它提供了有关地球上地幔中发生的部分熔融和熔体分离的信息。尽管人们知之甚少，但这些过程似乎是地球过去、现在和未来演化的基础。这次对霍罗曼橄榄岩的研究旨在帮助更好地了解这些过程。

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.