Observations on the relationship between crystallographic orientation and biasing in apatite fission-track measurements
Observations on the relationship between crystallographic orientation and biasing in apatite fission-track measurements
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磷灰石裂变径迹测量中晶体取向和偏差之间关系的观察
DOI：
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发表时间：
2003
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通讯作者：
R. Ketcham
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作者：
R. Ketcham
摘要通过对大量磷灰石裂变径迹实验数据的分析，揭示了晶体学取向对测量偏置影响的几个特征，这些特征以前并不清楚。在低水平的退火，各向异性在受限的轨道长度是最准确地描绘了一个椭圆形的分布，与两个建议的替代品相比。通过c轴投影对长度各向异性的量化进行了简化和改进，从而使模型更好地实现了在保留所有其他有用信息的同时去除各向异性的目标。在低退火水平的取向方面的观测频率的变化显示了一个大的，但迄今为止未报告的偏置因素有关的研究人员如何解释蚀刻不良的轨道。引入“蚀刻偏置”的概念来涵盖这种效应，其后果可能比先前研究的因素（如长度和蚀刻图形几何形状）大几个数量级。随着退火过程的进行，观测频率相对于角度的根本变化使另一个没有记录的过程变得明显：与c轴成大角度的轨道的相当大一部分完全退火。将这种损失纳入到以前的模型中，描述了受限轨道长度和密度之间的联系，改进了模型，使其预测现在接近于在单个种群的渐进退火中观察到的关系。由于蚀刻偏置效应与退火的方向和程度密切相关，因此未来开发严格的长度校准方案以支持热历史建模的任何努力都应明确考虑到这两个因素。
Abstract Analysis of extensive apatite fission-track experimental data reveals several features concerning the influence of crystallographic orientation on measurement biasing that had not been clear previously. At low levels of annealing, anisotropy in confined track lengths is most accurately depicted by an elliptical distribution, in comparison with two suggested alternatives. Quantification of length anisotropy by c-axis projection is simplified and improved, resulting in a model that better achieves its goal of removing anisotropy while preserving all other useful information. The variation of observational frequency of confined tracks with respect to orientation at low annealing levels reveals a large but heretofore-unreported biasing factor related to how an investigator interprets poorly etched tracks. The concept of an “under-etching bias” is introduced to encompass this effect, which can have consequences orders-of-magnitude greater than previously studied factors such as length and etch figure geometry. As annealing progresses, radical shifts in observational frequency with respect to angle make apparent another undocumented process: total annealing of substantial fractions of tracks oriented at high angles to the c axis. Incorporation of this loss into a previous model describing the link between confined track length and density improves the model such that its predictions are now close to the relationship observed in progressive annealing of a single population. Because under-etching biasing effects are intimately linked with orientation and extent of annealing, any future effort to develop a rigorous length calibration scheme to support thermal history modeling should take both of them explicitly into account.