The search for ultrahigh-pressure metamorphic bodies and analysis of their structures in the Himalayas and the Japanese islands

喜马拉雅变质带的研究通过对喜马拉雅西部地区的地质调查和岩石学研究，揭示了喜马拉雅变质带的构造格局。超高压变质岩单元（包括含硅质岩石）上覆和下伏于一般压力-温度条件下的变质岩单元。利用本项目2004年资助的“聚焦图像集成系统”进行显微岩石学观测，揭示了超高压榴辉岩中锆石的异常赋存。对榴辉岩的地球化学和年代学研究（冈山大学地球内部研究所访问研究项目）表明，榴辉岩的起源可以与三代玄武岩火山活动相关联（锆石U-Pb年龄分别为c. 267 Ma、c. 180.2 Ma和c. 114 Ma）。藏南（喜马拉雅山以北）的罗布沙蛇绿岩主要为地幔橄榄岩，含有金刚石等超高压指示矿物。现有地质资料结合显微岩石学观察表明，罗布沙蛇绿岩整体上为覆瓦覆盖构造。<霍罗曼橄榄岩体的研究b>北海道中部南部的霍罗曼橄榄岩体被认为是在Hidaka碰撞带形成期间从地幔中分离出来的。预计在橄榄岩体附近存在高压高温变质岩。对该橄榄岩体内部及周围进行了地质调查。在橄榄岩体的东北、南、东侧，确定了橄榄岩与片麻岩的界线，并分析了沿界线的变形构造。在橄榄岩体西侧的两个位置发现了橄榄岩与沉积岩的边界，并对沿边界的变形构造进行了分析。结合定向样品的微构造分析结果表明，霍罗曼橄榄岩体自东向西逆冲沉积岩。少

<Study of the Himalayan metamorphic belt>The geological survey and petrological study of the western part of the Himalayas reveals the tectonic setup of the Himalayan metamorphic belt (HMB). The ultrahigh-pressure metamorphic unit (including coesite-bearing rocks) is overlain and underlain by metamorphic units of common pressure-temperature conditions. Microscopic petrographical observations with "In-focus image integration system", which was equipped by this grant in 2004 and used for all microscopic observations in this study, reveal unusual occurrence of zircon in ultrahigh-pressure eclogite. The geochemical and geochronological studies of eclogites (under the Visiting Research Program of the Institute for Study of the Earth's Interior, Okayama University at Misasa) suggest that the origin of eclogites can be correlated with three generations of basaltic volcanic activity (zircon U-Pb ages of c. 267 Ma, c. 180.2 Ma and c. 114 Ma).<Study of the Luobusa ophiolite>The major part of the … More Luobusa ophiolite in the southern Tibet (north of the Himalayas) is mantle peridotite which includes ultrahigh-pressure indicating minerals such as diamond. The existing geological data combined with microscopic petrographical Dbservations reveal that the Luobusa ophiolite as a whole forms overturned imbricate structure.<Study of the Horoman peridotite body>The Horoman peridotite body in the southern part of central Hokkaido has been considered to be separated from the mantle during the formation of the Hidaka collision belt. Presence of high-pressure and high-temperature metamorphic rocks is expected in the vicinity of the peridotite body. Geological survey was carried out in and around the peridotite body. In the northeast, south and east sides of the peridotite body, the boundaries between peridotites and gneisses were located and deformation structures along the boundaries were analyzed. The boundaries between peridotites and sedimentary rocks were found at two locations in the western side of the peridotite body and deformation structures along the boundaries were analyzed. The results combined with microtectonic analysis of oriented samples suggest that the Horoman peridotite body thrust over the sedimentary rocks from the east to the west. Less