A set up of an atmosphere-controlled furnace with stirring device, and effect of stirring on the crystallization behavior of basaltic melts.

建造了一个带有搅拌装置的气氛控制炉。加热器为Siliconit DSP-26（螺旋SiC加热器），半径为56 mm，长度为300 mm。该炉的特点是样品内温度梯度小（30 ml铂坩埚，上直径36 mm）。炉内气氛由H2和CO2的混合气体控制，温度由使用Pt-PtRh热电偶的自动晶闸管炉控制器控制。炉温控制在2摄氏度以内，氧逸度在取样点的准确度在0.5巴对数单位以内。搅拌Pt管的直径为11 mm，并连接到陶瓷棒上，陶瓷棒以5-57 rpm的速率旋转。观察坩埚中的熔体，并从炉顶取样。样品用陶瓷棒手工取样，在空气中淬火，我们使用1778 A。D. Izu-Oshima，Japan的熔岩作为起始材料。采用静态线环法研究了合金的结晶行为和元素分配关系。样品首先在1250 ° C（高于液相线温度约50 ° C）下熔融10小时而不搅拌，然后在搅拌下以恒定速率冷却。斜长石从过热的玄武质熔体中成核的延迟已经被很好地证明（e. G. Gibb，1974 Min. Mag.）。在目前的实验中，CA。在10 ℃/小时的冷却速率下，对于57 rpm的旋转速率，斜长石成核需要35 ℃的过冷度。在1150 ℃下，斜长石样品的群体密度对于不搅拌的运行为4*10^4cm^<-3>，对于57 rpm的旋转速率的运行为7*10^5cm^<-3>，表明搅拌对玄武岩熔体中斜长石成核的影响。

An atmosphere-controlled furnace with stirring device was constructed. The heater is a Siliconit DSP-26 (spiral SiC heater) with radius of 56mm and length of 300mm. The furnace is characterized by small temperature gradient within the sample (30ml platinum crusible, with upper diameter of 36mm). The furnace atmosphere is controlled by mixed gas of H2 and CO2, and the temperature is controlled by an automatic thyristor furnace controller using a Pt-PtRh thermocouple. The furnace temperature is controlled within 2ﾟC and oxygen fugacity is accurate within 0.5 log unit of bars at the sample site. The stirring Pt pipe is 11mm in diameter and is attached to ceramic rod, which is rotated at a rate of 5-57 rpm. The melt in the crusible is observed and sampled from the top of the furnace. The sampling was made manually by a ceramic rod, and quenched in air.We used a 1778A. D. lava of Izu-Oshima, Japan, as a starting material. The crystallization behavior and element partition relation was investigated by static wire-loop method previously. The sample is first melted at 1250ﾟC (about 50ﾟC above the liquidus temperature) for 10 hours without stirring, and then cooled at constant rate with stirring. Delay of plagioclase nucleation from overheated basaitic melts has been well documented (e. g. Gibb, 1974 Min. Mag.). In the present experiment, ca. 35ﾟC undercooling was requirred for plagioclase nucleation for rotation rate of 57 rpm at a cooling rate of 10ﾟC/hr. Plagioclase population density at 1150ﾟC sample is 4*10^4cm^<-3> for a run without stirring, and 7*10^5cm^<-3> for a run with rotation rate of 57rpm, indicating an effect of stirring on the nucleation of plagioclase in a basaitic melt.