MK‐1 Apatite: A New Potential Reference Material for (U‐Th)/He Dating
MK‐1 Apatite: A New Potential Reference Material for (U‐Th)/He Dating
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DOI：
10.1111/ggr.12258
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发表时间：
2019-03
影响因子：
3.8
通讯作者：
Lin Wu;G. Shi;M. Danišík;Zhiyong Zhang;Yinzhi Wang;Fei Wang
中科院分区：
文献类型：
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作者：
Lin Wu;G. Shi;M. Danišík;Zhiyong Zhang;Yinzhi Wang;Fei Wang
几十年来，(U-Th)/He测年技术被广泛应用，以限制低温地质作用的时间。最近的研究表明，常用的参考材料(杜兰戈磷灰石)经常产生超出分析不确定度的分散碎片日期。本文报道了一种新的磷灰石(U-Th)/He测年标准物质MK-1，它是从缅甸莫谷变质带中采集的。两个随机选择的碎片的电子探针显微分析和背散射电子图像表明，这种磷灰石在化学和结构上都是均匀的。我们对这种材料的30个随机选择的碎片进行了单颗粒(U-Th)/He测年。来自多个实验室的(U-Th)/He测年结果表明，MK-1磷灰石巨晶碎片具有重现性，平均年龄为18.0±0.2 Ma。该磷灰石的Th/U值比较均匀。随机选择的9个碎片记录的有效铀(Eu)质量分数范围较窄(32 6~35 4μg g−1)，平均值为336.6±10 3μg g−1。所有结果表明，该磷灰石有可能成为(U-Th)/He年代学的新参考物质。
The (U‐Th)/He dating technique has been widely used for several decades to constrain the timing of low temperature geological processes. Recent research has shown that the commonly used reference material (the Durango apatite) often yields dispersed fragment dates that are beyond analytical uncertainties. Here, we report a new apatite (U‐Th)/He dating reference material, MK‐1, which was collected from the Mogok metamorphic belt in Burma. Electron probe microanalysis and backscattered electron images of two randomly selected fragments indicate that this apatite is chemically and structurally homogeneous. We performed single‐grain (U‐Th)/He dating on thirty randomly selected fragments of this material. (U‐Th)/He dating results from multiple laboratories show that fragments of the MK‐1 apatite megacryst yielded reproducible results, with a mean date of 18.0 ± 0.2 Ma. The Th/U ratio of this apatite is homogeneous. Nine randomly selected fragments registered a narrow range of effective uranium (eU) mass fractions (326–354 μg g−1), with a mean value of 336.6 ± 10.3 μg g−1. Twenty‐four in situ (U‐Th)/He dates yielded a mean value of 18.0 ± 0.2 Ma (MSWD = 0.41), indistinguishable from the results obtained by the conventional method. All the results suggest that this apatite has the potential to become a new reference material for (U‐Th)/He geochronology.