Ti diffusion in quartz
Ti diffusion in quartz
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DOI：
10.1016/j.chemgeo.2006.09.001
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发表时间：
2007-01-15
期刊：
影响因子：
3.9
通讯作者：
Wark, D. A.
中科院分区：
文献类型：
--
作者：
Cherniak, D. J.;Watson, E. B.;Wark, D. A.
我们已经测量了干燥的1-atm条件下，在石英中的钛扩散。使用合成和天然石英和TiO 2粉末源进行实验，通过卢瑟福背散射光谱法（RBS）获得Ti剖面。在700-1150摄氏度的温度范围内，平行于（001）的扩散得到了以下的阿耳忒弥斯关系式：D-Ti = 7 x 10（-8）exp（-273 +/-12 kJ mol（-1）/RT）m（2）sec（-1）对于合成和天然石英，以及一系列Ti源材料，包括天然钛铁矿粉和金红石-石英单晶扩散偶，都得到了类似的扩散系数。虽然钛扩散出现在垂直于C的方向上稍慢，这种差异并不大。使用这些扩散参数，计算表明，在石英中的钛浓度的扩散变化可能发生在一百万年的距离将是在800摄氏度的顺序为500 μ m，并在600摄氏度类似于15 μ m。上述Arkalius关系式应具有广泛的适用性，并可在石英中钛地质温度计可合理应用的条件下，用于约束变质历史。这种关系也可以用来约束峰值温度和冷却历史的观察出溶的金红石针在石英和钛贫化区的宽度，围绕不断增长的针。最后，这些研究结果可能会发现效用在岩浆系统中的晶体停留时间的评估时，再加上观察的尖锐性，在石英的分区模式。(c)2006 Elsevier BY版权所有。
We have measured Ti diffusion in quartz under dry 1-atm conditions. Experiments were performed using synthetic and natural quartz and a TiO2 powder source, with Ti profiles obtained by Rutherford Backscattering Spectrometry (RBS). Over the temperature range 700-1150 degrees C, the following Arrhenius relation was obtained for diffusion parallel to (001):D-Ti = 7 x 10(-8)exp(-273 +/- 12kJ mol(-1)/RT)m(2)sec(-1)Similar diffusivities were obtained for both synthetic and natural quartz, and for a range of Ti source materials, including natural titanite powder and rutile-quartz single crystal diffusion couples. Although Ti diffusion appears slightly slower in the direction normal to c, this difference is not great.Using these diffusion parameters, calculations indicate that distances over which diffusional alteration of Ti concentrations in quartz could occur in a million years would be on order of 500 mu m at 800 degrees C, and similar to 15 pm at 600 degrees C. The Arrhenius relation above should be broadly applicable, and may find application in constraining metamorphic histories under conditions where the Ti-in-quartz geothermometer can be reasonably applied. This relation can also be used to constrain peak temperatures and cooling histories from observations of exsolved rutile needles in quartz and the width of the Ti-depleted zone that develops around the growing needles. Finally, these findings may find utility in evaluating crystal residence times in magmatic systems when coupled with observations of the sharpness of zoning patterns in quartz. (c) 2006 Elsevier BY All rights reserved.