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Volume 77, Issue 10
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Masatoshi Shiba1982 Volume 77 Issue 10 Pages 345-355
Published: October 05, 1982
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSThe Tsukuba metamorphic area is underlain mostly by mica schists and gneisses derived from pelitic and psammitic sedimentary rocks of middle-late Triassic to late Jurassic. Three progressive zones A, B and C are classified on the basis of systematic variation of mineral parageneses. The representative assemblages of each zone are as follows.
A: muscovite+orthoclase+plagioclase+andalusite
B: fibrolite+muscovite+orthoclase+plagioclase+cordierite
C: fibrolite+orthoclase+plagioclase+cordierite+almandine
Biotite, quartz and graphite are found in almost all specimens studied. The geothermometry and geobarometry based on the dehydration reaction of muscovite and quartz, the polymorphic transition of Al2SiO5 minerals, the Fe-Mg partition between garnet and cordierite, and the two feldspar relation, enabled us to estimate the metamorphic con-ditions as 550° to 600°C, 3 to 4.5 Kb and 0.4-0.5 XH2O in the fluid phase.View full abstractDownload PDF (2757K) -
KOSUKE ONUMA1982 Volume 77 Issue 10 Pages 356-361
Published: October 05, 1982
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSThe join CaMgSi2O4 (diopside)-MgCr2O4 (picrochromite) is characterized by the presence of a wide picrochromite (MgCr2O4) primary field. The liquidus for diopsidess attains only 1.3 wt% MgCr2O4, keeping almost same temperatures, 1389±2°C, while the liquidus curve for picrochromite has a steep slope in the CaMgSi2O6-rich part. Diopsidess onephase field extends to 1.4 wt% MgCr2O4 at 1310°±5°C. Diopsidess melts incongruently to picrochromite+liquid. A small field of diopsidess+picrochromite+liquid is present between fields of picrochromite+liquid and diopsidess+picrochromite. The part richer in MgCr2O4 than 1.4 wt% consists of diopsidess and picrochromite at subsolidus temperatures. Diopsidess may contain CaCr2SiO6 and its composition does not lie on the join, indicating non-binary nature of the join.View full abstractDownload PDF (399K) -
Detrital garnets from pelitic Sanbagawa schists in the Bessi area, central ShikokuTOSHIO HIGASHINO, AKIRA TAKASU1982 Volume 77 Issue 10 Pages 362-367
Published: October 05, 1982
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSDetrital garnets were found from some pelitic schists in the garnet, albite-biotite and oligoclase-biotite zones of the Sanbagawa belt in the Bessi area, central Shikoku. They are subrounded to rounded, and are always armoured by the garnet formed at the Sanbagawa metamorphism. There is a distinct chemical discontinuity at the boundary between the detrital and Sanbagawa garnets, and some of the former have composition exotic to the pelitic Sanbagawa schists.View full abstractDownload PDF (1082K) -
Hiroshi Konno, Mizuhiko Akizuki1982 Volume 77 Issue 10 Pages 368-373
Published: October 05, 1982
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSIt was tried to fine a quantitative method of fluorine in topaz and tourmaline. Because both topaz and tourmaline are extremely difficult to be dissolved by acid, the specimens were fused by a flux composed of alkali carbonate before treatment by acid. Fluorine was separated from aluminum, silicon, boron and other elements by a steam distillation method using a mixture of sulfuric and phosphoric acid solutions. Finally, the fluorine was determined quantitatively using ion-selective electrode.
The optimum for the analyses was determined as follows: The specimen with sodium carbonate should be fused at 840°C for 10 minutes. Temperature of the solution should be kept in the range of 135 to l40°C during the distillation and the rate of distillation from 2 to 3 ml per minute. Fluorine contents of twelve topaz and six tourmaline crystals from various localities were determined by the above method.View full abstractDownload PDF (485K)
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