Annealing kinetics of fission tracks in zircon: an experimental study
Annealing kinetics of fission tracks in zircon: an experimental study
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DOI：
10.1016/0009-2541(95)00006-8
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发表时间：
1995-05
期刊：
影响因子：
3.9
通讯作者：
R. Yamada;T. Tagami;S. Nishimura;Hisatoshi Ito
中科院分区：
文献类型：
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作者：
R. Yamada;T. Tagami;S. Nishimura;Hisatoshi Ito
在350-750°C加热条件下，对锆石裂变径迹进行了10 - 1- 103小时（即4.5分钟-1040天）的一系列实验室退火实验。利用日沙台英安岩中的锆石颗粒测定了自发裂变径迹的受限长度的变化。归一化平均径迹长度（r）的衰减等值线在阿氏图上显示为一组直线。我们进行了一系列的模型拟合，称为平行和扇形模型，以描述r随温度或加热时间的增加而降低。锆石部分退火区（ZPAZ）的最低温度极限为r ≥ 0.95，最高温度极限为r ≥ 0.4，大致相当于表面径迹的总衰退。将实验室实验结果外推到地质时间尺度，对于106年的加热持续时间，ZPAZ的估计值为210-320°C（± 60°C，2σ）与平行模型; ± 190-350°C（± 50°C，2τ）;（±50°C，2σ）。ZPAZ的温度降低了1020 °C，退火持续时间长了一个数量级。由于锆石裂变径迹分析估计的闭合温度大致对应于ZPAZ的中部，因此这些结果支持先前估计的闭合温度为240°C。通过改变蚀刻时间，发现在r = 0.93时，α辐射损伤被显著去除。
A series of laboratory annealing experiments on zircon fission tracks has been carried out under heating conditions of 350–750°C for 10−1–103hr (i.e. 4.5 min-∼40 days). Variation in the confined lengths of spontaneous fission tracks was determined using zircon grains from Nisatai Dacite. The fading contours of normalized mean track length (r) on the Arrhenius diagram showed as sets of straight lines. We performed a series of model fittings, called the parallel and fanning models, in order to describe the decrease in r with increasing temperature or heating time. The lowest temperature limit of the zircon partial annealing zone (ZPAZ) was defined as r ≈ 0.95, and the highest as r ≈ 0.4, which approximately corresponded to the total fading of surface tracks. Extrapolation of the results of the laboratory experiments to the geological timescale gives, for a heating duration of 106 yr, estimated values of the ZPAZ of ∼210–320°C (± 60°C, 2σ) with the parallel model; ∼190–350°C (± 50°C, 2τ) with the fanning model (critical temperature, T0= ∞); and ∼170–390°C (±50°C, 2σ) with the fanning model (T0≠ ∞). The temperatures of the ZPAZ decrease by ∼20°C for an annealing duration that is an order of magnitude longer. Because the estimated closure temperature of zircon fission-track analysis approximately corresponds to the middle of the ZPAZ, these results support the previously estimated closure temperature of ∼240°C. By varying the etching time it was revealed that significant removal of α-radiation damage occurs at r ≈ 0.93.