Dealing with discordance: a novel approach for analysing U–Pb detrital zircon datasets
Dealing with discordance: a novel approach for analysing U–Pb detrital zircon datasets
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处理不一致：一种分析 U-Pb 碎屑锆石数据集的新方法
DOI：
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发表时间：
2016
影响因子：
2.7
通讯作者：
X. Rojas
中科院分区：
文献类型：
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作者：
J. Reimink;J. Davies;J. Waldron;X. Rojas
碎屑锆石U-Pb年代学是研究沉积岩记录的一种迅速发展和有用的技术。然而，由于评估不一致分析（在大多数数据集中很常见）的困难，很大比例的结果可能被丢弃。这些分析，如果解释正确，可以提供关于锆石种群的变形、蚀变或变质的有价值的信息，因为这些事件都能够产生U-Pb不一致。一种新的建模程序允许分析U-Pb数据集中的概率关系，通过评估潜在不一致线的相对可能性，对不一致分析中存在的年龄信息进行反卷积。此外，由于我们从不一致的数据中检索有用的信息，因此可以使用更严格的过滤器来评估一致性，从而增加对这些分布的信心。这种建模方法的有效性通过两个先前发表的来自加里多尼德造山带的案例来证明，其中存在明显不一致的分析。在苏格兰南部高地，这些分析表明，在奥陶系侵蚀和再沉积之前，格兰pian造山带变质沉积岩中的U-Pb系统发生了重置。在第二种情况下，来自格陵兰Caledonides的不一致数据为先前提出的在加拿大变形和流体流动事件期间的原位重置提供了额外的限制。补充材料：用于编写模型的代码以及指令指南可在http://doi.org/10.6084/m9.figshare.c.2182197上获得。
Detrital zircon U–Pb geochronology is a rapidly expanding and useful technique for addressing the sedimentary rock record. However, because of difficulties in evaluating discordant analyses, common in most datasets, a high proportion of results may be discarded. These analyses, if interpreted correctly, can provide valuable information regarding the deformation, alteration or metamorphism of the zircon population, as these events are all capable of producing U–Pb discordance. A novel modelling procedure permits analysis of probabilistic relationships within U–Pb datasets to deconvolve the age information present within discordant analyses by assessing the relative likelihood of potential discordia lines. Additionally, because we retrieve useful information from discordant data, a stricter filter can be used to assess concordance, increasing confidence in those distributions. The validity of this modelling method is demonstrated using two previously published cases from the Caledonide orogen where clearly discordant analyses exist. In the Southern Uplands of Scotland, these analyses indicate resetting of the U–Pb systematics in metasedimentary rocks in the Grampian orogen prior to Ordovician erosion and redeposition. In the second case, from the Greenland Caledonides, discordant data provide additional constraints on previously proposed in situ resetting during Scandian deformation and fluid flow events. Supplementary material: The code used for writing the model, along with an instruction guide, is available at http://doi.org/10.6084/m9.figshare.c.2182197.