Geology and petrology of volcanic conduits and lava domes

研究成果总结如下：1)对广泛分布于冲木群岛的粗面岩、粗面岩和流纹岩岩浆的成因及演化岩浆的火山导管特征进行了地质、岩石学和地球化学研究。有些流纹岩岩浆是在不同的P-T条件和部分熔融程度下由地壳物质部分熔融而产生的。岩浆混合发生在岩浆上升过程中或管道中。2)西三隐地区晚新生代玄武岩中存在含流纹岩成分的部分熔融玻璃的麻粒岩包体。这说明了晚新生代西三印地区具有长英质岩浆的生成潜力。3)通过给定温度和时间下的碳质木材的^<13>C/^<12>C同位素比值、H/C比值和红外光谱（吸收）估算火山碎屑流温度。^<13>C/^<12>C同位素比值没有得到，但H/C比值和红外光谱（吸收）是非常受影响的，特别是在低于400‰的情况下。4)从三音地区到九州北部，零星分布着许多英安岩成分的第四纪火山。从大森火山和三部火山到Taradake火山，再到大高山、青山和国崎半岛，发现了化学特征的系统差异。5)分析了三部英安岩熔岩和火山碎屑中火山玻璃的流体组分S、CO_2、Cl和F，探讨了喷发和非喷发长英质岩浆的关系。

Research results are summarized as follows : 1) Geological, petrographical and geochemical studies have carried out for origin of shoshonite, trachyte and rhyolite magmas, and features of volcanic conduits of evolved magmas which are widely distributed in the Oki Islands. Some rhyolite magmas were generated by partial melting of crustal materials under different P-T conditions and degree of partial melting. Magma mixing took place during uprising of magma or in conduit. 2) There are some granulite xenoliths including partial melt glasses with rhyolitic composition in late Cenozoic basalts in the west San'in region. This demonstrates the potential for generation of felsic magma beneath the west San'in region in late Cenozoic time. 3) The temperature of pyroclastic flow was estimated by ^<13>C/^<12>C isotope ratio, H/C ratio and infrared spectroscopy (absorption) of carbonaceous woods made under given temperature and times. ^<13>C/^<12>C isotope ratio is not available, but H/C ratio and infrared spectroscopy (absorption) are very affectable, especially in the case of less than 400ﾟC.4) Many Quanternary volcanoes with dacite compositions are sporadically distributed from the San'in region to northern Kyushu. Systematic differences of chemical characteristics are recognized from Daisen and Sambe volcanoes to Taradake volcano through Oetakayama, Aonoyama and Kunisaki Peninsula. 5) Fluid components, such as S,CO_2, Cl and F,in volcanic glass from Sambe dacite lava and pyroclstics have been analyzed for examination of relationship between eruption and non-eruption felsic magmas.