Kumar Prakash, Yuan Xiaohui, Kumar M Ravi, Kind Rainer, Li Xueqing, Chadha R K
National Geophysical Research Institute, Hyderabad 500 007, India.
Nature. 2007 Oct 18;449(7164):894-7. doi: 10.1038/nature06214.
The breakup of the supercontinent Gondwanaland into Africa, Antarctica, Australia and India about 140 million years ago, and consequently the opening of the Indian Ocean, is thought to have been caused by heating of the lithosphere from below by a large plume whose relicts are now the Marion, Kerguelen and Réunion plumes. Plate reconstructions based on palaeomagnetic data suggest that the Indian plate attained a very high speed (18-20 cm yr(-1) during the late Cretaceous period) subsequent to its breakup from Gondwanaland, and then slowed to approximately 5 cm yr(-1) after the continental collision with Asia approximately 50 Myr ago. The Australian and African plates moved comparatively less distance and at much lower speeds of 2-4 cm yr(-1) (refs 3-5). Antarctica remained almost stationary. This mobility makes India unique among the fragments of Gondwanaland. Here we propose that when the fragments of Gondwanaland were separated by the plume, the penetration of their lithospheric roots into the asthenosphere were important in determining their speed. We estimated the thickness of the lithospheric plates of the different fragments of Gondwanaland around the Indian Ocean by using the shear-wave receiver function technique. We found that the fragment of Gondwanaland with clearly the thinnest lithosphere is India. The lithospheric roots in South Africa, Australia and Antarctica are between 180 and 300 km deep, whereas the Indian lithosphere extends only about 100 km deep. We infer that the plume that partitioned Gondwanaland may have also melted the lower half of the Indian lithosphere, thus permitting faster motion due to ridge push or slab pull.
约1.4亿年前,超级大陆冈瓦纳大陆分裂成非洲、南极洲、澳大利亚和印度,印度洋随之开启,这一过程被认为是由一个大型地幔柱从下方加热岩石圈所致,其遗迹如今是马里恩、凯尔盖朗和留尼汪地幔柱。基于古地磁数据的板块重建表明,印度板块在从冈瓦纳大陆分裂后达到了非常高的速度(白垩纪晚期为18 - 20厘米/年),然后在约5000万年前与亚洲大陆碰撞后减缓至约5厘米/年。澳大利亚和非洲板块移动的距离相对较小,速度也低得多,为2 - 4厘米/年(参考文献3 - 5)。南极洲几乎保持静止。这种移动性使印度在冈瓦纳大陆的碎片中独一无二。我们提出,当冈瓦纳大陆的碎片被地幔柱分开时,它们岩石圈根部向软流圈的穿透对于确定其速度很重要。我们利用剪切波接收函数技术估算了印度洋周围冈瓦纳大陆不同碎片的岩石圈板块厚度。我们发现,冈瓦纳大陆中岩石圈明显最薄的碎片是印度。南非、澳大利亚和南极洲的岩石圈根部深度在180至300公里之间,而印度岩石圈仅延伸至约100公里深。我们推断,分裂冈瓦纳大陆的地幔柱可能也熔化了印度岩石圈的下半部分,从而由于洋中脊推力或板块拉力而允许更快的移动。