Influence of oxygen fugacity on the viscosity of CO2-, H2O-, and halogen-bearing basaltic melts

大洋中脊玄武岩的粘度与CO2含量、氧逸度、水含量和卤素含量的函数关系将在整个粘度范围内(10^0到10^12 PaS)使用落球和微渗透技术进行测定。当MORB从岩浆室上升形成水下枕状熔岩时，它脱掉并失去了一些水、二氧化碳和卤素含量。与此同时，岩浆所经历的氧逸度也发生了变化。取决于岩浆上升的速度，岩浆的化学条件可能与周围的条件平衡，也可能不平衡。在正确的氧逸度条件下，关于熔体流变性的研究很少。在这里，主要的主题是确定地球氧化还原条件下的粘度，并确定变化的氧化还原对粘度的影响。我们选择调查的挥发物范围从经常研究的水的影响，到较少研究的卤素影响，再到基本上未知的二氧化碳对粘度的影响。我们对二氧化碳影响的初步研究表明，它降低了熔体的粘度。这一观察结果与之前的一项研究(Morizet等人，2007年)的发现相反，在该研究中，发现二氧化碳对无铁声石熔体的玻璃化转变温度没有影响。

The viscosity of mid-ocean ridge basalt (MORB) as a function of CO2-content, oxygen fugacity, water content and halogen content will be determined across the entire viscosity range (10^0 to 10^12 Pa s) using falling-sphere and micropenetration techniques. As MORB rises from the magma chamber to form sub-aqueous pillow lavas, it degasses and loses some of its water, CO2, and halogen content. At the same time the oxygen fugacity experienced by the magma changes. Depending upon how fast the magma rises, the chemical condition of the magma may or may not be in equilibrium with the surrounding conditions. There are very few studies of the rheology of melts at the correct oxygen fugacity conditions. Here, the major theme is to determine viscosity at the redox conditions of the Earth, and to determine the effects of changing redox on viscosity. The volatiles we have chosen to investigate range from the often studied effects of water, to the less studied effects of halogens to the essentially unknown effects of CO2 on viscosity. Our preliminary study on the effect of CO2 shows that it decreases the viscosity of the melt. This observation is contrary to that found in a previous study (Morizet et al., 2007) in which CO2 was found to have no effect on the glass transition temperature of an iron-free phonolite melt.