ARGON DIFFUSION CHARACTERISTICS OF PYROXENES

在2000年夏天， Proterozoic Mafic Intrusive从加拿大安大略省收集了28个网站的主题部分。在核反应堆中，新鲜正氮和clinopyroxene颗粒被分离和扭曲，运送到40 Ar/39 Ar日期，通过自动激光温度控制快速和精确地结合当前测量，我们建造了一个自动激光器步进加热40 Ar/39 Ar日期的系统，并改进了数据统计数据。一个自动XYZ阶段控制器在11月完成，并且一个程序也在开发中进行了连续的引脚点测量。在测量期间，一个动量从一个蒸汽样品中释放，在激光脉冲的辐射导致了一个薄层的移动。这破坏了取样点的对齐。一个薄薄的部分被金属（钛）洗涤器用重量打磨。这个新方法允许你用发射的光执行薄节日期。在2001年，几个激光步骤加热实验已经开始了。不同年龄的光谱经常从同样的岩石中发现的焦氮颗粒。一种方法来测定在40 Ar/39 Ar的日期中给予平板电脑的方法，但没有稳定。幽门螺杆菌的扩散参数从实验中计算，估计的封闭温度接近450-C，其中比生物质和麝香菌更高，低于角布。这将使幽门螺杆菌具有重要的作用，即热仪。这些结果将在第九届关于实验矿物学、矿物学和地质化学的国际研讨会上提出（瑞士苏黎世）。

In the summer of 2000, Proterozoic mafic intrusives were collected from 28 sites in themiddle part of Ontario, Canada. Fresh orthopyroxene and clinopyroxene grains were separated, and irradated in a nuclear reactor to carry out 40Ar/39Ar dating.Combining fast and accurate ion current measurement with an automatic laser temperaturecontrol, we built an automatic laser step heating 40Ar/39Ar dating system, which improved the statistics of data. An automatic XYZ stage control was purchased in November, and a program to carry out continuous pin point measurements were also developed. During the measurements, a momentum from a vaporized sample released during the irradiation of a laser pulse causes a move of the thin section. This destroys the alignment of sampling points. A thin section were sandwitched with metal (titanium) washers by its weight. This new method allows to perform thin section dating with transmitted light.In 2001, several laser step heating experiments were carried out. Different age spectrawere often obtained from pyroxene grains in the same rock. A method to distinguish pyroxene samples which give plateaux in 40Ar/39Ar dating has not been established. Diffusion parameters of pyroxenes were calculated from the experiments, and estimated closure temperature was approximately 450ーC, which is higher than that of biotites and muscovites, and lower than hornblendes. This implies a significant role of pyroxene as a thermochronometer. These results will be presented in the ninth internatinal symposium on experimental mineralogy, petrology and geochemistry (Zurich, Switzerland).