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首页> 外文期刊>Contributions to Mineralogy and Petrology >Discrimination of TiO2 polymorphs in sedimentary and metamorphic rocks
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Discrimination of TiO2 polymorphs in sedimentary and metamorphic rocks

机译：沉积和变质岩中TiO 2 多晶型的判别

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Investigation by Raman spectroscopy of samples from different geological settings shows that the occurrence of TiO2 polymorphs other than rutile can hardly be predicted, and furthermore, the occurrence of anatase is more widespread than previously thought. Metamorphic pressure and temperature, together with whole rock chemistry, control the occurrence of anatase, whereas variation of mineral assemblage characteristics and/or fluid occurrence or composition takes influence on anatase trace element characteristics and re-equilibration of relict rutiles. Evaluation of trace element contents obtained by electron microprobe in anatase, brookite, and rutile shows that these vary significantly between the three TiO2 phases. Therefore, on the one hand, an appropriation to source rock type according to Nb and Cr contents, but as well application of thermometry on the basis of Zr contents, would lead to erroneous results if no phase specification is done beforehand. For the elements Cr, V, Fe, and Nb, variation between the polymorphs is systematic and can be used for discrimination on the basis of a linear discriminant analysis. Using phase group means and coefficients of linear discriminants obtained from a compilation of analyses from samples with well-defined phase information together with prior probabilities of groupings from a natural sample compilation, one is able to calculate phase grouping probabilities of any TiO2 analysis containing at least the critical elements Cr, V, Fe, and Nb. An application of this calculation shows that for the appropriation to the phase rutile, a correct-classification rate of 99.5% is obtained. Hence, phase specification by trace elements proves to be a valuable tool besides Raman spectroscopy.
机译：通过拉曼光谱法对来自不同地质背景的样品的研究表明，除了金红石型以外，几乎无法预测到TiO 2 多晶型物的发生，而且，锐钛矿的发生比以前想象的要广泛。变质压力和温度以及整个岩石化学作用控制了锐钛矿的发生，而矿物组合特征和/或流体的发生或组成的变化会影响锐钛矿的微量元素特征和残余金红石的重新平衡。通过电子微探针在锐钛矿，板钛矿和金红石中获得的痕量元素含量的评估表明，在三个TiO 2 相之间，这些元素的含量差异很大。因此，一方面，如果不事先确定相，则根据Nb和Cr含量来选择烃源岩类型，但根据Zr含量来应用测温法也会导致错误的结果。对于元素Cr，V，Fe和Nb，多晶型之间的变化是系统性的，可用于基于线性判别分析的判别。使用相组均值和线性判别系数，这些线性判别系数是从具有明确定义的相信息的样品的分析汇编中获得的，以及从自然样品汇编中获得分组的先验概率，从而能够计算任何TiO 2的相分组概率分析至少包含关键元素Cr，V，Fe和Nb。该计算的应用表明，对于金红石相的分配，获得了99.5％的正确分类率。因此，除拉曼光谱法外，痕量元素的相位鉴定被证明是一种有价值的工具。

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