We describe a major shear zone exposed at Akebono Rock and discuss its deformation and metamorphic history, with a view to providing a better understanding of the geological history of the Lützow-Holm Complex. Three deformation episodes are recognized: D1 produced open folds (F1), boudinage and a regional ductile foliation, whilst the related metamorphic facies is characterized by stable garnet. F1 folding is dominantly preserved in the eastern part of the study area. During D2, an isoclinal to tight asymmetric F2 folds developed mainly in the west part of the region, accompanied by an S2 shear, under biotite facies retrograde metamorphism. The D3 episode involved the formation of the major shear zone, characterized by mylonite and L-tectonite fabrics, which took place at ~610–660°C and 4–5 kbar. Large, sigmoidal garnet core domains have S-shaped inclusion trails, suggesting that syntectonic garnet growth occurred before the formation of the shear zone. Estimated P-T conditions suggest that the sigmoidal garnet-bearing amphibolite was recrystallized at a deeper crustal level and was brought to a higher level during the formation of the shear zone. Crustal-scale deformation involving syntectonic recrystallization and shearing of Akebono Rock is a key issue for reconsidering the evolution of the Lützow-Holm Complex.

中文翻译：

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东南极洲Lützow-Holm杂岩体Akebono岩的构造-变质演化及剪切带岩性意义

我们描述了曙光岩暴露的一个主要剪切带，并讨论了它的变形和变质历史，以期更好地了解 Lützow-Holm 复合体的地质历史。识别出三个变形阶段：D1 产生开放褶皱（F1）、布丁和区域韧性叶理，而相关的变质相以稳定的石榴石为特征。F1褶皱主要保存在研究区东部。D2期，在黑云母相逆行变质作用下，主要在该地区西部发育等斜到致密的非对称F2褶皱，并伴有S2剪切。D3 事件涉及主要剪切带的形成，其特征是糜棱岩和 L-构造岩织物，发生在 ~610-660°C 和 4-5 kbar。大，S形石榴石核心域具有S形包裹体轨迹，表明同构造石榴石生长发生在剪切带形成之前。估计的PT条件表明，含S形石榴石的角闪岩在更深的地壳水平上再结晶，并在剪切带的形成过程中上升到更高的水平。涉及曙光岩同构造再结晶和剪切的地壳尺度变形是重新考虑吕措-霍尔姆杂岩演化的关键问题。