@article{oai:nipr.repo.nii.ac.jp:00002638,
 author = {オオバ, タカノブ and シライシ, カズユキ and OBA, Takanobu and SHIRAISHI, Kazuyuki},
 journal = {Proceedings of the NIPR Symposium on Antarctic Geosciences},
 month = {Sep},
 note = {P(論文), The melting relationships of five syenites from the Yamato and Sør Rondane Mountains were determined in the temperature range of 650-850℃, under the water pressure of 1-2 kbar and oxygen fugacities of the FMQ buffer. The syenites studied are samples from the Yamato Mountains (Nos. 73120904 : Y904 and 73120405 : Y405) and from the Sør Rondane Mountains (Nos. 85012101A : SR-A, 85012103B : SR-B and 85012103C : SR-C). They are composed of porphyritic K-feldspar, plagioclase, quartz, biotite, Ca-amphibole or Ca-Na amphibole, clinopyroxene, sphene, ilmenite and rarely magnetite. Though the syenites from both regions consists of the same mineral assemblages, the compositions of amphiboles are various as follows; Ca-amphibole in the syenite (Y904) from the Yamato Mountains is close to edenitic. On the other hand, the bluish green hornblende in the mafic layer (SR-B) and the leucocratic layer (SR-C) from the Sør Rondane Mountains is richteritic actinolite. In the porphyritic syenite (Y405) and the leucocratic syenite (SR-A) intruding the layered syenites (SR-B and SR-C), the Ca-amphibole is pargasitic hornblende. The solidus temperatures of the syenites from the Sør Rondane Mountains are about 770℃ at 1 kbar. With increasing temperature, plagioclase (albite) and quartz disappeared in the lower temperature range than K-feldspar, hornblende, biotite and clinopyroxene. Clinopyroxene, biotite and K-feldspar are stable at 850℃ under the water pressure of 1 kbar. Richteritic actinolite in two layered syenites (SR-B and SR-C) becomes unstable at slightly higher temperature than solidus at 1 kbar. Pargasitic hornblende from syenite (SR-A) is stable at 825℃ and 1 kbar, and it disappears at 775℃ and 1.7 kbar. Representative results of syenites from the Yamato Mountains at 1 kbar are : clinopyroxene quartz syenite (Y904) begins to melt at 680℃, quartz and plagioclase disappear at 710℃, edenitic hornblende disappears at 775℃, K-feldspar disappears at 825℃, clinopyroxene hornblende quartz syenite (Y405) begins to melt at 760℃, plagioclase and quartz disappear at 780℃, K-feldspar disappears at 830℃, hornblende appears at 850℃. In both rocks, clinopyroxene and biotite remain at 850℃. The composition of edenitic hornblende shifts to actinolite-pargasite join with increasing temperature under water pressure. The result suggests that edenite end member is unstable under high water pressure in a preliminary synthesized experiment. Pargasitic hornblende from two syenites (SR-A and Y405) are both stable at 825℃ and 1 kbar. At 1.6 kbar the hornblende (Y405) is stable at 825℃, while the other hornblendes is unstable at 800℃.All rocks investigated are at least 40% melted at temperatures 50℃ above the solidus. The approximate K-feldspar content of the syenite is about 30%. The compositions of K-feldspar are Ab_<40>Or_<60> and Ab_5Or_<95> at 800℃ and 700℃, respectively. As compared to biotite, the behavior of K-feldspar is important to concentrate K_2O content of syenite.},
 title = {EXPERIMENTAL STUDY OF THE SYENITIC ROCKS FROM THE YAMATO AND SØR RONDANE MOUNTAINS, EAST ANTARCTICA},
 volume = {4},
 year = {1990}
}