Sulfur supplies of arc volcanoes from frontal to back-arc-sulfur contents of melt inclusions in phenocrysts

研究表明，岛弧火山俯冲相关岩浆具有较高的硫浓度。基性岩浆预计会为火山岩浆系统提供大量的硫，而硫在火山喷发时释放出来。在熔融包裹体研究的基础上，研究了从火山前缘到弧后的火山岩岩浆系统的主要成分特征，并估算了其硫供应。1)对北海道西南部至东北至中部地区沿火山锋的多座火山的橄榄石斑晶中所含的硫及其熔融包裹体的主要成分进行了显微探针分析。注入火山下长英质岩浆室的镁质岩浆显示出含水和高硫浓度。镁质岩浆在熔体包裹橄榄石斑晶之前呈囊泡状。2)弧后区橄榄石斑晶中的熔体包裹体硫含量相对较低，斑晶（橄榄石和辉石）包裹体为高k_2o熔体。3)对硫进行了探针分析，对H2O进行了傅里叶红外分析，确定了橄榄石斑晶中熔体包裹体的硫- x射线峰移，并尝试开发了一些熔体包裹体研究的方法。

Our research project revealed that subduction related magmas of island arc volcanoes have high sulfur concentrations. Mafic magmas are expected to supply large amounts of sulfur to the volcanic magma system, and the sulfur is released during eruptions. We investigated the characteristics of major components and estimate sulfur supplies in the magma systems of volcanics from the volcanic front to back-arc, based on melt inclusion studies.1)we performed microprobe analyses of sulfur as well as major components of melt inclusions trapped in olivine phenocrysts from many volcanoes along the volcanic front from southwest Hokkaido through Tohoku to Chubu areas. Mafic magmas injected into the felsic chamber beneath the volcanoes is indicated to be hidrous and have large sulfur concentration. The mafic magmas were vesiculated before the melt entrapment in olivine phenocrysts.2)In the back-arc areas, on the other hand, melt inclusions in olivine phenocrysts have relatively low sulfur concentration, and phenocrysts (olivine and pyroxene) trapped high-K_2O melt inclusions.3)We performed microprobe analysis for sulfur, FTIR analysis for H2O, determine Sulfur-Xray peak shift of the melt inclusions trapped in olivine phenocrysts, and tried to develop some methods in the melt inclusion study.