Tectono-metamorphic evolution and significance of shear-zone lithologies in Akebono Rock, Lutzow-Holm Complex, East Antarctica
Tectono-metamorphic evolution and significance of shear-zone lithologies in Akebono Rock, Lutzow-Holm Complex, East Antarctica
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东南极Lutzow-Holm杂岩曙岩构造变质演化及剪切带岩性意义
DOI：
10.1017/s0954102020000450
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发表时间：
2020
影响因子：
1.6
通讯作者：
Dashbaatar Davaa-Ochir
中科院分区：
文献类型：
--
作者：
Baba Sotaro;Hokada Tomokazu;Kamei Atsushi;Kitano Ippei;Motoyoshi Yoichi;Nantasin Prayath;Setiawan Nugroho Imam;Dashbaatar Davaa-Ochir
我们描述了一个主要的剪切带暴露在Akebono岩石，并讨论其变形和变质历史，以期提供一个更好地了解Lützow-Holm复杂的地质历史。三个变形幕被确认：D1产生开放的褶皱（F1），石香肠和区域韧性叶理，而相关的变质相的特点是稳定的石榴石。F1褶皱主要保存在研究区东部。在D2期间，在黑云母相退变质作用下，主要在该地区的西部发育等斜至致密不对称的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-构造岩组构，其发生在约610-660°C和4-5 kbar。大，S形石榴石核心域有S形夹杂物的痕迹，这表明同构造石榴石生长发生在剪切带形成之前。估计的P-T条件表明，S形石榴斜长角闪岩重结晶在地壳较深的水平，并在剪切带的形成过程中被带到更高的水平。涉及同构造重结晶和Akebono岩剪切的地壳规模变形是重新考虑Lützow-Holm杂岩演化的关键问题。
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.