Abstract Microstructural investigations of mantle xenoliths from the Mt. Melbourne area were undertaken to reveal the origin of S-wave splitting beneath northern Victoria Land, Antarctica. The six analyzed peridotites contain various deformation features. The rotated olivine maxima of [100] and [010] into horizontal and vertical orientations, respectively, are classified into five samples with a D-type crystallographic preferred orientation (CPO) and one sample as an A-type CPO. The D-type olivine fabric can be explained by multiple slip systems of {0kl}[100] at low-temperature and high-stress conditions; therefore, both compressional and extensional regimes during subduction and rifting, respectively, could be applied in this study. With an assumption that olivine a-axes are aligned along the direction of mantle flow to form maximum S-wave splitting, the observed delay time of 0.9–1.3 s beneath northern Victoria Land can be partially explained by the existence of mantle peridotites. The remaining seismic anisotropy can be explained by the presence of melt pockets trapped along tectonic faults that developed perpendicular to the fast S-wave splitting direction. This study therefore demonstrates that the NE–SW-trending S-wave splitting beneath northern Victoria Land, Antarctica, results from the existence of both mantle peridotites as well as melt pockets trapped along the tectonic faults.

中文翻译：

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从 Mt. 附近的橄榄岩捕虏体推断出北横贯南极山脉下的上地幔地震各向异性。墨尔本，维多利亚州北部，南极洲

摘要 山地幔包体的显微结构研究。墨尔本地区被用来揭示南极洲维多利亚地北部下方 S 波分裂的起源。六个分析的橄榄岩包含各种变形特征。[100] 和 [010] 的旋转橄榄石最大值分别为水平和垂直取向，分为五个具有 D 型晶体择优取向 (CPO) 的样品和一个作为 A 型 CPO 的样品。D型橄榄石织物可以用{0kl}[100]在低温和高应力条件下的多重滑移系统来解释；因此，俯冲和裂谷过程中的压缩和拉伸机制分别适用于本研究。假设橄榄石 a 轴沿地幔流动方向排列以形成最大 S 波分裂，在维多利亚州北部观察到的 0.9-1.3 秒延迟时间可以部分解释为地幔橄榄岩的存在。剩余的地震各向异性可以通过沿垂直于快速 S 波分裂方向发展的构造断层中存在的熔池来解释。因此，这项研究表明，南极洲维多利亚地北部下方的 NE-SW 向 S 波分裂是由于地幔橄榄岩和沿构造断层被困的熔体的存在。剩余的地震各向异性可以通过沿垂直于快速 S 波分裂方向发展的构造断层中存在的熔池来解释。因此，这项研究表明，南极洲维多利亚地北部下方的 NE-SW 向 S 波分裂是由于地幔橄榄岩和沿构造断层被困的熔体的存在。剩余的地震各向异性可以通过沿垂直于快速 S 波分裂方向发展的构造断层中存在的熔池来解释。因此，这项研究表明，南极洲维多利亚地北部下方的 NE-SW 向 S 波分裂是由于地幔橄榄岩和沿构造断层被困的熔体的存在。