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首页> 外文期刊>Contributions to Mineralogy and Petrology >Extended planar defects and the rapid incorporation of Ti4+ into olivine
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Extended planar defects and the rapid incorporation of Ti4+ into olivine

机译：扩展的平面缺陷和Ti4 +快速掺入橄榄石中

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The formation of extended planar defects in minerals such as olivine is related to high point defect concentration and can be driven by large gradients in chemical potential, where the energy of the system is lowered by the ordering of defects along specific planes in the crystal. The presence of extended defects has the potential to create the (apparently) anomalous ionic diffusion in olivine as reported recently (Spandler and O’Neill in Contrib Mineral Petrol 159(6):791–818, 2010). High-resolution transmission electron microscopy and energy-filtered imaging were done using experimental samples designed to examine the impact of a TiO2 and f O2 on the potential to form such defects in ferromagnesian olivine. Doped basalt (5 wt% TiO2)–olivine reaction couple experiments were run at 1 atm and 1,310 and 1,410 °C for 50 h at various f O2, ranging from 102 below to 102 above the quartz–fayalite–magnetite buffer. Our results show that extended planar defects in olivine, parallel to {101}ol and occurring in ordered “clusters” with a prolate spheroid geometry ~5–25 nm across and extending up to 150 nm into the olivine, are present near the olivine–glass interfaces in all of our experimental high-TiO2 basalt–olivine samples. Increased Ti content in the olivine is associated with the defects; ordering of Ti4+ and octahedral site vacancies leads to a two- or three-layer superstructure in the olivine. Defect nucleation and growth is driven by the large TiO2 chemical potential gradient across the phase boundary at the start of the experiments, which provides access to microstructures not otherwise present.
机译：矿物（例如橄榄石）中扩展的平面缺陷的形成与高点缺陷浓度有关，并且可以由化学势的大梯度来驱动，在该过程中，系统的能量因沿晶体中特定平面的缺陷排序而降低。正如最近报道的那样，存在延伸缺陷的可能性有可能在橄榄石中造成（明显的）异常离子扩散（Spandler和O'Neill在Contrib Mineral Petrol 159（6）：791–818，2010）。使用实验样品进行了高分辨率透射电子显微镜和能量过滤成像，这些实验样品旨在检查TiO2和f O2对铁锰矿橄榄石中形成此类缺陷的可能性的影响。掺杂的玄武岩（5 wt％TiO2）-橄榄石反应耦合实验在1 atm和1,310和1,410°C下以各种f O2进行了50 h，范围从石英-铁橄榄石-磁铁矿缓冲液的下方102到上方102。我们的结果表明，在橄榄石附近存在与{101} ol平行的橄榄形扩展平面缺陷，出现在椭圆形的球状几何体中，呈椭圆形，长约5–25 nm，并延伸到橄榄石中，呈有序的“簇状”。我们所有的实验性高TiO2玄武岩-橄榄石样品中的玻璃界面。橄榄石中钛含量的增加与缺陷有关。 Ti4 +和八面体位空位的有序性导致橄榄石中的两层或三层超结构。在实验开始时，相界上较大的TiO2化学势梯度会驱动缺陷成核和生长，这为进入微结构提供了可能。

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