PDF(Pubmed)
Abstract：
As relics of ancient ocean lithosphere, ophiolites are the most important petrological evidence for marking the sutures and also play a key role in reconstructing plate configuration. They also provide valuable windows for studying crustal accretion and mantle processes occurring at modern ocean ridges. Abundant ophiolites are distributed along the Yarlung-Tsangpo suture and represent the relics of ocean lithosphere of the Neo-Tethys. They are characterized by an incomplete litho-stratigraphy, of which the mantle section is much thicker than the crustal section. Ocean crustal rocks outcropped in the Yarlung-Tsangpo ophiolites are much thinner than normal ocean crusts (~ 7 km) or even absent. Tectonic settings from which the Yarlung-Tsangpo ophiolites originated remain highly controversial, although an origin of the supra-subduction zone is prevailing. Moreover, their incomplete litho-stratigraphy has been commonly attributed to tectonic dismemberment during the late-stage emplacement after their formation. Nevertheless, such an incompleteness resembles the ocean lithosphere generated at modern ultraslow spreading ridges, such as the Southwest Indian Ridge (SWIR). In this paper, we present several lines of evidence that support the formation of the Yarlung-Tsangpo ophiolites at ultraslow spreading ridges, during which detachment faults were developed. This suggests that the Yarlung-Tsangpo ophiolites might represent the ocean core complexes (OCC) in the Neo-Tethys Ocean. The OCC with high topography in the seafloor were clogged in the trench and preserved as ophiolites through Indo-Eurasia collision. The clogging resulted in the demise of an old subduction and a new subduction was re-initiated beneath the clogged OCC.
摘要：
作为古代海洋岩石圈的遗迹，蛇绿岩是标记缝合线的最重要的岩石学证据，并且在重建钢板配置中也起着关键作用。它们还为研究现代洋脊上发生的地壳增生和地幔过程提供了宝贵的窗口。大量的蛇绿岩沿着雅鲁藏布缝合线分布，代表了新特提斯海洋岩石圈的遗迹。它们的特征是不完整的岩石地层学，其中地幔部分比地壳部分厚得多。Yarlung-Tsangpo蛇绿岩中出现的海洋地壳岩石比正常的海洋地壳（〜7km）薄得多，甚至没有。雅鲁藏布蛇绿岩起源的构造环境仍然存在很大争议，尽管上俯冲带的起源盛行。此外，它们不完整的岩性地层通常归因于它们形成后后期的构造分裂。然而，这种不完整性类似于在现代超缓慢扩张的山脊上产生的海洋岩石圈，例如西南印度岭（SWIR）。在本文中,我们提供了几行证据，支持在超缓慢扩张的山脊上形成Yarlung-Tsangpo蛇绿岩，在此期间形成了分离断层。这表明Yarlung-Tsangpo蛇绿岩可能代表了新特提斯海洋中的海洋核心复合物（OCC）。海底高地形的OCC在海沟中被堵塞，并通过印度-欧亚大陆碰撞保存为蛇绿岩。堵塞导致旧俯冲的消亡，并在堵塞的OCC下方重新开始了新的俯冲。
