The cation distribution of major and minor elements over the two non-equivalent sites in olivine and its temperature dependence.

阳离子分配系数K_D(=(Fe/mg)&lt；m1&gt；/(Fe/mg)_&lt；M2&gt；)镁橄榄石的K_D值玄武岩为0.95~1.13，超镁铁质结核为1.01~1.12，流纹岩为1.18，变质岩为0.95，H6球粒陨石为0.91。总体上，火山橄榄石对M_1位有轻微的偏好性，变质橄榄石对M_2位有轻微的偏好性。高温X射线原位实验表明，加热后的橄榄石的K_D值随温度升高而增大，600ﾟC以上的K_D值随铁闪石含量的增加而增大。这些结果表明，高温下橄榄石中的阳离子交换并不迟缓，冷却时高温下的阳离子分布不会被保存下来。橄榄石在室温下的K_D值不受赋存状态的明显区别。利用ALHEMI(原子通道增强显微分析)技术，在Akaslii EM-002B透射电子显微镜上，带有EDAX9100和双倾斜样品支架，测定了阳离子在橄榄石中两个阳离子中心的分布。一组适合电子悬崖的平面。Ling在Pbnm设置中为(002)。文中推导了以硅原子为参比原子确定晶位占有率的新公式。镁和铁分别表现出对M2和M1位的轻微偏爱。微量元素Ni和Mn分别对M_1位和M_2位表现出强烈的偏好性。

The cation distribution coefficients K_D (=(Fe/Mg)_<M1>/(Fe/Mg)_<M2>) were calculated from the X-ray site occupancy refinements for olivines. The K_D values of Mg, Feolivines obtained are 0.95-1.13 in basalt, 1.01-1.12 in ultramafic nodule, 1.18 in rhyolite, 0.95 in metamorphic rocks atid 0.91 in H6-chondolite. As a whole, the volcanic olivines have the slight preference of Fe for the Ml site, and the metamorphic olivines for the M2 site, as the previous investigators reported.In-situ high temperature X-ray experiments showed that the K_D values of the heated olivines increased with increasing temperature, and that values above 600 ﾟC increase with increasing fayalite content. Ttiese results suggest that tile cation exchange in olivine is not sluggish at high temperature and the cation distribution at high temperature is not preserved on cooling. Ttierefdre the K_D values at room temperature for olivines are riot obviously distinguished by the modes of occurrence.Using ALHEMI (Atomic Location by CHanneling Enhanced MIcroanalysis) technique, with an Akaslii EM-002B TEM having EDAX9100 and double tilt specimen holder, the distribution of cations over the two cation sites in olivine is determined. A suitable set of planes for electron clianrie. ling is(002)in Pbnm setting. Here, the new equation for the calculation to determine the site occupancies, using Si atom as reference atom, is derived. Mg and Fe show a slight preference for the M2 and M1 sites respectively. Minor elements Ni and Mn show a strong preference for the M1 site and the M2 site respectively.