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Volume 80, Issue 12
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YASUKO OKUYAMA-KUSUNOSE1985 Volume 80 Issue 12 Pages 515-525
Published: December 05, 1985
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSMargarite occurs in the low-grade zone of the contact aureole of the Tono granitic mass, Kitakami Mountains, Northeast Japan, coexisting with muscovite, paragonite, chlorite and quartz, but without carbonates and feldspars. The margarite is produced by the reaction between pyrophyllite and zoisite in the progressive metamorphism at a temperature near the upper stability limit of the assemblage margarite +quartz. The solubility of muscovite component in paragonite in the three white micas is suppressed as compared to that in the muscovite-paragonite assemblage, whereas the paragonite solubility in muscovite of the three-phase assemblage is similar to that of the two-phase assemblage. Paragonite component in margarite in three-phase assemblage of this area is about 17.3-22.5 mol% ; this value is the smallest for the margarite in three-phase assemblages so far reported. The low paragonite solubility of margarite in this area is probably due to the low pressure condition of the contact metamorphism of the Tono area.View full abstractDownload PDF (1572K) -
Yukito Oda, Shunichi Suzuki, Yoshihiko Oyama1985 Volume 80 Issue 12 Pages 526-536
Published: December 05, 1985
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSCore samples from 18 boreholes in the area southeast of the Lake Towada were investigated to determine expandability of mica/smectite in the Miocene sediments. The expandability decreases with depth from about 80 to 0% over intervals of 100 to 400m in the western part of the area, while intervals of more than 600m in the eastern part. The percentage of expandable layers in mica/smectite decrease from east to west. The expandable layer isopleth map at the top of the Yotsuzawa Formation shows a decrease in expandable layers from 80 to 10% at a distance of about 500m. The conversion of smectite to mica/smectite mixed layers begins at 0.6-0.8% vitrinite reflectivity, and the conversion to the 10% of expandable layers occurs in 1.2-2.8% vitrinite reflectivity.
Stratiform ore bodies of Kuroko and copper-lead-zinc veins are restricted to the zone less than 20% of expandable layers at the top of the Yotsuzawa Formation. The expandability of mica/smectite mixed layer in sediments is useful as a guide to mineral exploration.View full abstractDownload PDF (745K) -
Asahiko Sugaki, Kiyoshi Isobe1985 Volume 80 Issue 12 Pages 537-540
Published: December 05, 1985
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSK-Ar ages of adularia from epithermal gold-silver quartz veins of the Sanru and Koryu mines which belong to Kitami and South-western metallogenetic provinces in Hokkaido respectively, have been determined. Adularia occurs as band, 2 to 5mm in width, in crustified banding quartz associating with dark colored gold-silver bearing band (Ginguro). A K-Ar age of 12.4±0.6 Ma was obtained for adularia from the -120m level of the Juji vein, Sanru mine, whereas adularia from the 20m sublevel of the 60m level of the No. 1 vein, Koryu mine, gave a K-Ar age of 1.0±0.3 Ma. The former age corresponds to the Middle Miocene and suggests that one of mineralization of gold-silver in the Kitami metallogenetic province occurred that period. The age of 1.0±0.3 Ma for the Koryu mine is a youngest age for gold-silver mineralization in Japan according to all K-Ar age data for epithermal vein up to the present as given in Table 1, and it is significant to note that a hydrothermal mineralization which produced a gold-silver quartz vein in Hokkaido occurred in the Pleistocene age, as nearly the same time as that of the Hishikari and Ohra mines in the northern Kagoshima of Kyushu, Japan.View full abstractDownload PDF (321K)
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