| Project/Area Number |
63540639
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
鉱物学(含岩石・鉱床学)
|
|---|
| Research Institution | HIROSAKI UNIVERSITY |
|---|
Principal Investigator |
ONUKI Hitoshi Hirosaki University, Faculty of Science, Professor, 理学部, 教授 (00004317)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
SASAKI Minoru Hirosaki University, Sciences, Faculty of Science, Assistant, 理学部, 助手 (00196180)
SHIBA Masatoshi Hirosaki University, Faculty of Science, Lecturer, 理学部, 講師 (80125442)
|
|---|
| Project Period (FY) |
1988 – 1989
|
| Project Status |
Completed (Fiscal Year 1989)
|
| Budget Amount *help |
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1989: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1988: ¥1,000,000 (Direct Cost: ¥1,000,000)
|
|---|
| Keywords | Green Tuff hydrothermal alteration / Alteration of Miocene basaltic rocks / Zeolite to prehnite-pumpellyite facies assemblages. / Hydrothermal metamorphism / グリ-ンタフ熱水変質作用 / 中新世玄武岩類の変質 / 低温熱水変質作用 / 中新世の低温 / 低圧変成作用 / サブ緑色片岩相 / 低温変成鉱物の化学組成 |
|---|
| Research Abstract |
This project was undertaken in order to understand better the secondary mineralization of the Miocene submarine lavas and pyroclastic rocks with basaltic to andesiiic compositions during the "Green Tuff alteration". The Hanaoka area of the Akita Prefecture, and the Okiura, Hakamagoshi-dake and Kanita areas of the Aosorl Prefecture were selected for this purpose in the northern part of the Northeast Japan. Drilling has confirmed that the Miocene basaltic piles developed in the Hanaoka and Okiura areas are at least 700 meters thick. Their thickness in the other areas are estimated to be more than a few hundred meters. The metabastes in these four areas well preserved their original textures and primary phases such as clinopyroxene and plagioclase, but they have been recrystallized to varying degrees at low temperatures, resulting in the formation of various secondary minerals.
In the Hanaoka and Okiura areas, the metabastes are characterized by the assemblage of chlorite + epidote + pumpellyite + prehnite at the surface exposures, but chlorite + epidote + prehnite + actinolite in the deep drill core, in addition to albite and quartz. Zeolites occur only in veins and amygudules of the samples from the surface exposures. Ca-zeolites are laumontite and yugawaralite in the Hanaoka area and wairakite, laumontite and yugawaralite in the Okiura area. In the Hakamagoshi-dake and Kanita areas, chlorite, epidote, prehnite, and pumpellyite in the matrices and in pseudomorphs after plagioclase. Actinolite rarely occurs as overgrowth on relict clinopyroxene crystal in the Kanita area. Characteristic Ca-zeolites are laumontite, stilbite and heulandite in veins and amygudules in both areas.
These Miocene rocks have been extensively subjected to the "Green Tuff" hydrothermal metamorphism. Their fossil geothermal gradients of more than 100ﾟC/km would be estimated in these four areas.
|
