1998 Fiscal Year Final Research Report Summary
The pressure estimated by amphibole geobarometer in syenite and granil
| Project/Area Number |
09640567
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Petrology/Mineralogy/Science of ore deposit
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| Research Institution | Joetsu University of Education |
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Principal Investigator |
OBA Takanobu College of Education Research Assistants, 学校教育学部, 助手 (30194278)
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| Co-Investigator(Kenkyū-buntansha) |
WATANABE Takashi Joetsu University of Education, College of Education Professor, 学校教育学部, 教授 (00037269)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Amphibole / Geobarometer / Granite / Syenite / Synthetic Experiment |
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| Research Abstract |
We attempt to estimate the pressure of amphibole-bearing syenites and granitic rocks in the range 600ﾟC -930ﾟC under a water pressure from 0.05GPa to 0.34GPa and oxygen fugacitied of the FMQ buffer. The stability limit curve of amphibole changes its P-T slope from positive at low pressure to negative at high pressure, and it intersects with a solidus of syenite and granite at two pressure points. We suggest that amphibole in syenite from the Yamato Mountains could have crystallized at pressres less than 0.3GPa (depth : -10 km), probably in a shallow crustal magma chamber.
Hammarstrom and Zen (1986, 1992) proposed an empirical correlation between the estimated pressures of crystallization of calc-alkaline plutons and the total Al content of horublende. However, in the present experiments, the chemical composition of amphibole near solidus does not change. We reported that the pargasite content in amphibole increases with increasing temperature. If we compared with amphiboles synthesized at different temperatures, amphibole geobarometer is considerable uncertainty. We attempt the partitioning of Na, Al, Mg and Fe between amphibole and pyroxene.
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