近日，丹麦哥本哈根大学William R. Hyde及其课题组成员取得一项新突破。他们研究报道了格陵兰西北部发现ca.1Ga超高速撞击事件的证据。相关论文于2024年4月12日发表在《地质学》杂志上。

据研究人员介绍，地球上可能有许多未被发现的撞击结构，一些挑战阻碍了人们对它们的探测，包括其可能隐藏在大冰盖之下。近年来，格陵兰西北部冰川下ca.58Ma撞击结构的地球物理、地球化学和微物理证据不断增加。

研究人员报告了该地区第二次，更古老的超高速撞击事件的证据，即从冰川河流沉积物中收集到撞击熔融的岩石样本。冲击变质锆石颗粒的二次离子质谱U-Pb分析得出了此前未记录的元古代最佳撞击年龄估计值，为1039±16Ma(加权偏差均方=2.9)。

根据从未受撞击的锆石颗粒获得的太古代-元古代目标岩石U-Pb年龄，以及沿冰缘的熔融岩石样本的位置，研究人员认为该样本来自于更深入内陆的超高速撞击结构，被格陵兰冰盖所掩盖。这项研究证明了人们在地球上一些最难以到达的地区发现新的撞击事件的能力，以及在检查非原位材料时从一个地点对多个撞击结构采样的可能性。研究结果对研究当前和未来返回的火星和月球样本具有重要意义，这些样本显然具有更复杂的撞击历史。

附：英文原文

Title: Evidence for ca. 1 Ga hypervelocity impact event found in northwest Greenland

Author: William R. Hyde, Gavin G. Kenny, Steven J. Jaret, Joseph A. MacGregor, Pierre Beck, Martin J. Whitehouse, Nicolaj K. Larsen

Issue&Volume: 2024-04-12

Abstract: There are likely many undiscovered impact structures on Earth, but several challenges prevent their detection, including possible concealment beneath large ice sheets. In recent years, geophysical, geochemical, and microphysical evidence has mounted for a ca. 58 Ma impact structure under the Hiawatha Glacier, northwest Greenland. Here, we report evidence for a second, much older hypervelocity impact event in this region, recorded in an impact melt rock sample collected from a glaciofluvial deposit in Inglefield Land. Secondary ion mass spectrometry U-Pb analyses of shock metamorphosed zircon grains yielded a previously unrecorded, Proterozoic best estimate impact age of 1039 ± 16 Ma (mean square of weighted deviates = 2.9). Based on ArcheanProterozoic target rock U-Pb ages obtained from unshocked zircon grains and the location of the melt rock sample along the ice margin, we suggest this sample was derived from a hypervelocity impact structure farther inland, concealed by the Greenland Ice Sheet. This study demonstrates the ability to uncover new impact events in some of the most inaccessible areas on Earth and the possibility of sampling multiple impact structures from one location when examining ex situ material. Our results have implications for current and future Martian and lunar returned samples that demonstrably bear complex impact histories.

DOI: 10.1130/G51876.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G51876.1/638076/Evidence-for-ca-1-Ga-hypervelocity-impact-event