Eruption mechanisms and crystal textures

1.亚液相线岩浆的粘度测量：亚液相线岩浆中含有各种形状和大小的晶体，它们对体积粘度的影响以前没有研究过。我们安装了一个带有粘度计的气氛控制炉，测量了体积粘度，并通过玻璃分析评估了熔体粘度，分析了晶体结构。富士火山的1707高铝玄武岩具有斜长石作为液相线相，并且非常薄的斜长石板条导致偏离常用的Einstein-Roscoe-Marsh方程4倍。另一方面，九州西北部的碱性橄榄玄武岩以橄榄石为液相线相，20vol%的较薄斜长石的存在并没有引起ERM方程的偏离，这可以通过估算Krieger-Doughnard方程中的参数来解释。2.通过高压实验对1991 - 1995年云仙火山英安岩的端元岩浆混合条件进行了评价，并测定了云仙英安岩中Cl/OH在角闪石和熔体之间的分配系数，结果表明分配系数与角闪石的Mg/（Mg + Fe）比值有很强的相关性。这一结果表明，温仙英安岩中振荡环带角闪石斑晶Cl含量的显著变化是由低温岩浆中流体相的反复脱气和输入引起的。另一项对云仙英安岩的实验表明，Cl的存在增加了硫的溶解度。3.实验研究了压力和含水量对斜长石和玄武岩熔体之间Ca-Na分配系数的影响，高金斜长石的最佳结晶条件为2 - 3kb水饱和条件。对镁质火山岩进行了地球化学和岩石学研究。

1.Viscosity measurement of subliquidus magmas : Subliquidus magmas contain crystals of various shapes and size, and their effect on bulk viscosity has not been studied previously We installed an atmosphere-controlled furnace with viscometer, and measured bulk viscosity with concominant sampling, and evaluated the melt viscosity from the glass analyses, and analyzed the crystal textures. The 1707 high-alumina basalt of Fuji volcano has plagioclase as liquidus phase, and very thin plagioclase laths caused deviation from the commonly-used Einstein-Roscoe-Marsh equation by a factor of 4. On the other hand, an alkali olivine basalt of NW Kyushu has olivine as liquidus phase and presence of 20 vol% of mildly thin plagioclase did not cause deviation from the ERM equation, which can be explained by evaluating the parameters in the Krieger-Dougherty equation.2.We evaluated the conditions of the end member magmas of magma mixing for the 1991-1995 dacite of Unzen volcano by high-pressure experiments, and also conducted experiments to determine the Cl/OH partition coefficient between hornblende and melt in the Unzen dacite, showing the strong dependence of the partition coefficient on the Mg/(Mg+Fe) ratio of hornblende. This result suggest that marked variation of Cl content of oscillatory zoned hornblende phenocryst in the Unzen dacite was caused by repeated degassing and input of fluid phase in the low-temperature magmas. Another experiments on the Unzen dacite showed solubility of sulfur is increased by the presence of Cl.3.Effect of pressure and water content on the Ca-Na partition coefficient between plagioclase and basaltic melt was evaluated experimentally, and it was shown that optimal condition for crystallization of high-An plagioclase is 2-3kb water saturated condition in arc tholeiite.4.Genetic conditions of high-magnesian volcanic rocks are examined geochemically and petrologically.