Abstract Interpretation of apatite fission-track length data rests on the assumptions that etching fully reveals latent tracks, and that laboratory annealing of induced tracks constitutes a good proxy for geological annealing of spontaneous tracks. Recent work using improved step-etching procedures questions both of these assumptions. Step etching experiments interrogating the etching structure of tracks near and beyond their tips have shown that tracks are often not etched to their full extent of latent track damage in a standard single-step, 20-s etch, and that the etching structure in this outer region differs between fossil and induced tracks. In this study, we develop a more complete picture of track revelation for fossil and unannealed and annealed induced tracks in Durango apatite. Using first steps as early as 10 s after the beginning of etching, we discern differences in etching structure between various track types, and document a gradual fall-off in etching velocity from the track interior toward its tips. When effective etching time is constrained by selecting earlier-etching confined tracks for later analysis, mean lengths are longer, but length dispersion is not diminished. Although some proportion of unannealed tracks are under-etched after 20 s of etching, with increased levels of annealing the probability of an induced track being fully etched increases. We use an etch-anneal-etch procedure, consisting of partially etching tracks, annealing the apatite grains, and then continuing etching, to establish bulk etching rates at track tips. Bulk etching is effectively isotropic, as is etching velocity in the central portions of tracks, away from their tips. We use our data to compare two end-member possibilities for along-track etching structure, which provides a first step toward a deeper understanding of annealing and development of a more robust standard etching protocol.

中文翻译：

---

磷灰石裂变径迹的顺径蚀刻结构：观察和启示

摘要 磷灰石裂变径迹长度数据的解释基于蚀刻完全揭示潜在径迹的假设，并且诱导径迹的实验室退火构成了自发径迹地质退火的良好代表。最近使用改进的阶梯蚀刻程序的工作对这两个假设提出了质疑。询问接近和超出其尖端的轨迹的蚀刻结构的步进蚀刻实验表明，在标准的单步 20 秒蚀刻中，轨迹通常不会被蚀刻到其潜在的轨迹损坏的全部范围，并且该外部的蚀刻结构化石轨迹和诱发轨迹之间的区域不同。在这项研究中，我们对杜兰戈磷灰石中化石、未退火和退火诱发轨迹的轨迹揭示进行了更完整的描述。最早在蚀刻开始 10 秒后使用第一步，我们辨别出各种轨道类型之间蚀刻结构的差异，并记录了从轨道内部到其尖端的蚀刻速度逐渐下降。当有效蚀刻时间因选择较早蚀刻的受限轨迹用于后期分析而受到限制时，平均长度会更长，但长度离散并不会减少。尽管在蚀刻 20 秒后，一定比例的未退火轨道蚀刻不足，但随着退火水平的增加，诱导轨道被完全蚀刻的可能性也会增加。我们使用蚀刻-退火-蚀刻程序，包括部分蚀刻轨迹、对磷灰石晶粒进行退火，然后继续蚀刻，以在轨迹尖端建立体蚀刻速率。体蚀刻实际上是各向同性的，轨道中心部分的蚀刻速度也是如此，远离它们的尖端。我们使用我们的数据来比较沿轨道蚀刻结构的两种终端成员的可能性，这为更深入地了解退火和开发更强大的标准蚀刻协议迈出了第一步。