In this paper, we report a new metamorphic age for kyanite-bearing garnet-biotite gneiss collected from Akebono Rock, which is located on Prince Olav Coast, in the Lützow-Holm Complex (LHC), East Antarctica. The metamorphic P–T path estimated from pseudosection modeling, together with garnet compositional zoning and experimentally calibrated geothermobarometry, suggests that the gneiss underwent a clockwise amphibolite-facies P–T history. Two populations of U–Pb zircon ages of 1121–1014 Ma and 972–904 Ma (n = 65) were identified, with the latter population having a weighted mean age of 937 ± 6 Ma. The younger population was dated from overgrowth rims and single zircon grains interpreted as metamorphic in origin. Ti-in-zircon thermometry supports crystallization of these zircon domains and grains at a temperature close to the metamorphic peak of 642 °C at 937 Ma. Monazite EMP dating from the other four samples show an age between 977–917 Ma. These lines of evidence indicate that prograde metamorphism of the Akebono Rock gneiss occurred during the Tonian, that is, substantially earlier than the LHC regional metamorphic age of late Neoproterozoic to Cambrian. Our results indicate that a fundamental revision of the sequence of metamorphic events in the Prince Olav Coast area of the LHC is required. We also identified three possible relationships between Akebono Rock and other geological units that record Tonian metamorphism, although we cannot determine which relationship is most likely. In particular, linear magnetic anomalies were identified near the boundary between the LHC and the Western Rayner Complex/inland nunataks of western Enderby Land, suggesting the presence of geological discontinuities.

在本文中，我们报告了从位于南极洲东部吕佐霍姆复合体 (LHC) 奥拉夫王子海岸的曙光岩中收集的含蓝晶石的石榴石-黑云母片麻岩的新变质时代。从伪剖面模型估计的变质P-T路径，连同石榴石成分分区和实验校准的地温气压计，表明片麻岩经历了顺时针角闪岩相P-T历史。确定了两个年龄为 1121-1014 Ma 和 972-904 Ma（n = 65）的 U-Pb 锆石种群，后者的加权平均年龄为 937 ± 6 Ma。较年轻的种群从过度生长的边缘和被解释为变质起源的单个锆石颗粒确定年代。锆石中的钛测温支持这些锆石域和晶粒在接近 937 Ma 的 642 °C 变质峰的温度下结晶。其他四个样品的独居石 EMP 显示年龄在 977-917 Ma 之间。这些证据表明，曙光岩片麻岩的前行变质作用发生在托尼阶，即远早于晚新元古代至寒武纪的大型强子对撞机区域变质时代。我们的结果表明，需要对 LHC 的奥拉夫王子海岸地区的变质事件序列进行根本修订。我们还确定了曙岩与其他记录托尼安变质作用的地质单元之间的三种可能关系，尽管我们无法确定哪种关系最有可能。特别是，在 LHC 和西部雷纳复合体/恩德比地西部的内陆 nunatak 之间的边界附近发现了线性磁异常，表明存在地质不连续性。