@misc{oai:niigata-u.repo.nii.ac.jp:00005321,
 author = {田中, 真二},
 month = {Sep},
 note = {The Poroshiri ophiolite is exposed in the western side of the Hidaka metamorphic belt, central Hokkaido. Metamorphism in the ophiolite is studied in its northern part (Chiroro River area) to elucidate relationship between metamorphic and large-scale folding structure and fault movement. Along the northern E-W transect, the ophiolite succession in the western area forms an isoclinal anticline while that in the eastern area bounded by a N-S trending fault shows an open syncline. Along the southern E-W transect, upper sequence of the ophiolite is exposed in the eastern part along a NW-SE trending thrust fault. The metamorphic grades change steeply from the greenschist to amphibolite facies at the western margin, then gently increases to 600 ℃ toward the central fault along the northern transect, while the metamorphic temperature in the east of the central fault, is kept around 700 ℃. Consequently there is a temperature gap, about 100 ℃ at the central fault. Because the fold structure of the ophiolire in the northern transect is discordant with the metamorphic thermal structure, peak of the metamorphism should be later than the folding. The central fault was still active after the peak of metamorphism to cause the temperature gap. The metamorphic temperature of the upper sequence of the ophiolite in the eastern part along the southern transect is about 600 ℃ similar to the eastern margin of the western part along the northern transect. This suggests that the upper sequence along the southern transect was brought from the western part after the peak of metamorphism along the NW-SE trending thrust fault. The reaction rim consisiting orthopyroxene, pargasite and spinel is observed along olivine and plagioclase boundary. Metamorphic conditions of formation of this reaction rim are estimated 4-6 kb and 650-720 ℃. This reaction rim has not been reported from normal seafloor metamorphism. Therefore it is implied that the Porohisiri ophiolite is underwent in 4-6 kb and 650-720 ℃ after the formation of the oceanic crust. This metamorphism occurred due to ridge subduction before the cooling of the oceanic crust. The amphibole pornhyroclasts pervasively show marked prograde zoning, but they do not show retrograde zoning. This resulted from a short duration of exhumation after the peak of metamorphism. This metamorphism observed in the Porohisiri ophiolite is quite different from ordinary regional metamorphism., 学位の種類: 博士（理学）. 報告番号: 甲第3698号. 学位記番号: 新大院博（理）甲第356号. 学位授与年月日: 平成24年9月20日, 新大院博（理）甲第356号},
 title = {ポロシリオフィオライト北部地域の変成作用 : 2回の変成作用の特徴と変成プロセス},
 year = {2012}
}