Variation in apatite fission-track length measurement: implications for thermal history modelling
Variation in apatite fission-track length measurement: implications for thermal history modelling
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DOI：
10.1016/s0009-2541(02)00423-0
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发表时间：
2003-07-30
期刊：
影响因子：
3.9
通讯作者：
Carter, A
中科院分区：
文献类型：
--
作者：
Barbarand, J;Hurford, T;Carter, A
使用磷灰石裂变径迹（FT）数据的预测热历史建模依赖于描述FT退火的时间和温度依赖性的算法，该算法又依赖于作为退火过程的量度的FT长度的经验确定。FT长度测量的变异性评估描述不佳，分析员之间的比较很少，实验室间的标准化也很少。使用磷灰石的各种组合物含有诱导轨道退火到不同程度，这项研究评估了各种程序conditions.Replicate分析的水平限制轨道长度测量的变化，由一个单一的观察者通常是在3%以内，但与轨道长度成反比增加。相同样品的观察者之间的比较显示了观察者之间显著的、通常非系统的变化;对于复杂的长度分布，变化类似于12%。变异的来源被确定为：（a）来自径迹显示的变异，包括蚀刻、径迹中径迹（TINT）与解理中径迹（TINCLE）测量以及使用Cf-252辐照产生额外的蚀刻通道;（B）测量偏差，包括设备、分析程序和样本量;和（c）观察者的偏见，主要是个人技术的差异和一致性。5 M HNO 3优于较弱的蚀刻剂：尽管各向异性更强，但是轨迹被更好地限定，允许更严格的测量，而C轴平行截面（其中2 π/4 π几何形状被更好地限定）更容易识别。除了最长的长度分布，TINCLEs明显长于TINTS，在高角度下很少有短TINCLEs; TINCLEs的测量有效地掩盖了退火的各向异性。Cf-252辐照可有效增加TINT采样和测量的数量。未辐照和Cf辐照等分试样的测量值之间的变化不超过单个分析员的测量值，尽管观察到Cf辐照样品向较长长度的轻微系统性偏移。正如其他工作者所报道的，径迹长度分布是各向异性的，各向异性随着退火水平的增加而增加。轨道角度施加的测量长度的主要影响，从退火和蚀刻各向异性与观察者的偏见的影响求和。退火算法中应考虑径迹角度，建议采用与退火实验相似的径迹显示、观测和测量条件分析现场样品，并随后用于数值模型以预测热历史。对于使用相似成分的样品，可以提出一个平行的论点。此外，我们建议，FT社区应寻求作为一个紧迫的问题，使用标准磷灰石样品的轨道长度测量的实验室间比较的方案，含有典型的人工长度分布的各种复杂程度。这种比较将为地质案例研究中的热历史预测提供更严格的基线。(C)2003 Elsevier Science B. V.保留所有权利。
Predictive thermal history modelling using apatite fission-track (FT) data is dependent on an algorithm to describe the time and temperature dependency of FT annealing which, in turn, relies on the empirical determination of FT length as a measure of the annealing process. Assessment of variation in FT length measurement is poorly described, with few comparisons between analysts and little interlaboratory standardisation. Using apatites of various compositions containing induced tracks annealed to differing degrees, this study has assessed variation in horizontal confined track-length measurement for a variety of procedural conditions.Replicate analysis by a single observer is typically within 3% but increases inversely with track length. Comparison between observers on the same samples shows significant, generally nonsystematic variation between observers; for a complex length distribution variation is similar to 12%. Sources of variation are identified as: (a) variation from track revelation, including etching, track-in-track (TINT) vs. track-in-cleavage (TINCLE) measurement and use of Cf-252 irradiation to produce additional etching channels; (b) bias in measurement, including equipment, analytical procedures, and sample size; and (c) observer bias, principally differences in and consistency of personal technique.5 M HNO3 of is preferred to weaker etchants: although more anisotropic, tracks are better defined, permitting more rigorous measurement, while c-axis parallel sections (where 2 pi/4 pi geometry is better defined) are more easily identified. For all but the longest length distributions, TINCLEs are significantly longer than TINTS, with few short TINCLEs at high angles; measurement of TINCLEs effectively masks the anisotropy of annealing. Cf-252 irradiation is effective in increasing the number of TINTs sampled and measured. Variation between values measured for unirradiated and Cf-irradiated aliquots does not exceed that found for a single analyst, although a slight systematic shift to longer lengths for Cf-irradiated samples is seen. As reported by other workers, track-length distributions are anisotropic, anisotropy increasing with annealing level. Track angle exerts a major influence on measured length, summing affects from annealing and etching anisotropies with observer bias. Track angle should be accommodated within the annealing algorithm.It is recommended that similar track revelation, observation and measurement conditions are used for the analysis of field samples as are used in annealing experiments, and subsequently employed in numerical models to predict thermal history. A parallel argument can be advanced for using samples of similar composition. Further, we recommend that the FT community should seek as a matter of some urgency a programme of interlaboratory comparison of track-length measurement using standard apatite samples containing artificial length distributions typifying various levels of complexity. Such comparisons would provide a more rigorous baseline for thermal history prediction in geological case studies. (C) 2003 Elsevier Science B.V. All rights reserved.