Geology and petrology of volcanic conduits and lava domes

1)对广泛分布于冲绳群岛的玄武岩、粗面岩、流纹岩岩浆的成因及演化岩浆的火山通道特征进行了地质、岩石学和地球化学研究。一些流纹岩岩浆是由地壳物质在不同的温压条件和部分熔融程度下部分熔融而成的。岩浆混合发生在岩浆上升过程中或在管道中。2)西三宁地区晚新生代玄武岩中有部分麻粒岩包体，包括流纹岩成分的部分熔融玻璃。这显示了晚新生代在西萨宁地区地下产生长英质岩浆的可能性。3)利用碳质木材在一定温度和时间下的~(13)&gt；C/~(12)&gt；C同位素比值、氢/碳比值和红外吸收光谱估算了火山碎屑流的温度。13&lt；13&gt；C/^&lt；12&gt；C同位素比值不可用，但H/C比和红外光谱(吸收)非常有影响，特别是在小于400ﾟ的情况下C.4)许多英安岩成分的第四纪火山零星地分布在桑宁地区到九州北部。从Daisen火山、Sambe火山到Taradake火山，再到大山、青山和库尼萨基半岛，化学特征的系统差异被识别出来。5)对桑贝英安岩熔岩和火山碎屑岩中的火山玻璃中的S、CO_2、Cl、F等流体成分进行了分析，以探讨火山喷发与未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.