Hot mantle plumes and ancient cold slabs have been observed beneath modern mid-ocean ridges, but their specific and detailed effects on mid-ocean ridge crustal accretion are poorly understood. The oceanic lithosphere beneath the Southeast Indian Ocean displays unique morphological, geophysical, and geochemical characteristics, which may reflect the influence of both mantle anomalies and upwelling plumes on seafloor spreading. In this study, we combined gravity-derived oceanic crustal thickness with plate tectonic reconstructions to investigate patterns of asymmetry in thickness of crust accreted at the Southeast Indian Ridge over the last 50 m.y. Our results reveal several distinct features: (1) small-scale, short-lived asymmetries in the thickness of crustal accretion of up to 0.75 km are alternatively distributed on the southern and northern flanks of the 90°–120°E Southeast Indian Ridge segment. These can be explained by variations in mantle depletion or mantle temperature. (2) Two large-scale, long-lived (duration of ∼50 m.y.) asymmetries in crustal accretion of >2.5 km are observed around the Kerguelen Plateau and Balleny Islands, which we attribute to excess crust from the off-axis Kerguelen and Balleny mantle plumes. (3) Two large-scale, long-lived (duration of ∼50 m.y.) asymmetries in crustal accretion of 0.75–2.5 km are observed on the northern flank of the westernmost (70°–80°E) Southeast Indian Ridge and the southern flank of the eastern (120°–140°E) Southeast Indian Ridge segment, respectively. We attribute these to asymmetry in mantle temperature of up to 20–53 °C. We suggest these asymmetric temperatures across the Southeast Indian Ridge are associated with the foundered lithospheric fragments of the Indian Craton triggered by the African Large Low-Shear-Velocity Province during the breakup of Gondwanaland and an intraplate subducted slab of the Paleo-Tethys Ocean, respectively. The remnant craton fragments and subducted oceanic slab may have moved north in concert with the northward-migrating Southeast Indian Ridge beginning at 50 m.y. ago.

中文翻译：

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由于地幔深部异常，东南印第安海脊地壳增厚的大规模不对称性

在现代中洋海脊之下已经观察到热的地幔柱和古老的冷平板，但是人们对它们对中洋海脊地壳增生的具体和详细的​​影响知之甚少。东南亚印度洋下面的海洋岩石圈显示出独特的形态，地球物理和地球化学特征，这可能反映出地幔异常和上升流羽对海床扩散的影响。在这项研究中，我们将重力衍生的海洋地壳厚度与板块构造重建相结合，以研究过去50年来印度洋东南脊积聚的地壳厚度的非对称性模式。我们的结果揭示了几个明显的特征：（1）小规模，地壳增厚厚度的短时不对称性最高为0。在90°–120°E东南印度洋脊段的南部和北部侧面，也有75 km分布。这些可以通过地幔消耗或地幔温度的变化来解释。（2）在Kerguelen高原和Balleny群岛周围观察到两个大于2.5 km的地壳长距离的长寿命（持续时间约50 my）不对称现象，我们认为这是由于离轴的Kerguelen和Balleny地壳过多所致。地幔柱。（3）在最西端（70°-80°E）东南印度洋脊的北翼和0.75°-2.5 km的地壳增生中观测到两个大规模，长寿命（持续时间约50 my）的不对称现象。东南部（120°–140°E）东南印度洋脊段的侧面。我们将这些归因于地幔温度高达20–53°C的不对称性。我们认为这些东南印度洋脊的不对称温度分别与冈瓦纳大陆破裂和古特提斯洋板内俯冲板块在非洲大范围低剪切速度省份引发的印度克拉通的碎裂的岩石圈碎片有关。 。残余的克拉通碎片和俯冲的海洋板块可能已经与我北上50年前开始向北迁移的东南印第安海岭一起向北移动。