Geology Department, Juniata College, Huntingdon, PA, USA.
Earth and Environmental Science, James Cook University, Townsville, QLD, Australia.
Nat Commun. 2021 Jul 5;12(1):4128. doi: 10.1038/s41467-021-24419-8.
Numerous geochemical anomalies exist at the K-Pg boundary that indicate the addition of extraterrestrial materials; however, none fingerprint volatilization, a key process that occurs during large bolide impacts. Stable Zn isotopes are an exceptional indicator of volatility-related processes, where partial vaporization of Zn leaves the residuum enriched in its heavy isotopes. Here, we present Zn isotope data for sedimentary rock layers of the K-Pg boundary, which display heavier Zn isotope compositions and lower Zn concentrations relative to surrounding sedimentary rocks, the carbonate platform at the impact site, and most carbonaceous chondrites. Neither volcanic events nor secondary alteration during weathering and diagenesis can explain the Zn concentration and isotope signatures present. The systematically higher Zn isotope values within the boundary layer sediments provide an isotopic fingerprint of partially evaporated material within the K-Pg boundary layer, thus earmarking Zn volatilization during impact and subsequent ejecta transport associated with an impact at the K-Pg.
在 K-Pg 边界存在许多地球化学异常，表明有天外物质的加入；然而，没有一种物质能标记挥发作用，这是在大型陨石撞击过程中发生的关键过程。稳定的锌同位素是与挥发作用相关过程的一个特殊指标，其中锌的部分蒸发会使残留物富含重同位素。在这里，我们提供了 K-Pg 边界沉积岩层的锌同位素数据，这些数据显示，与周围的沉积岩、撞击地点的碳酸盐台地以及大多数碳质球粒陨石相比，这些沉积岩层的锌同位素组成更重，锌浓度更低。火山活动或风化和成岩作用过程中的次生变化都不能解释目前存在的锌浓度和同位素特征。边界层沉积物中系统地更高的锌同位素值为 K-Pg 边界层中部分蒸发物质提供了一个同位素指纹，从而标记了撞击过程中的锌挥发作用以及随后与 K-Pg 撞击相关的喷射物运输。
