近日，英国牛津大学R. Kounoudis团队研究了过去裂谷在大火成岩省发展中的重要性。2025年11月5日出版的《自然》杂志发表了这项成果。

通常认为，岩石圈薄弱带（如近期夭折的裂谷）是裂谷作用和大火成岩省发育过程中岩浆活动与变形集中的弱势区域。然而，东非Turkana坳陷作为6600万年前夭折的Anza裂谷所在地，虽在4500万年前区域遭遇地幔柱热物质时处于岩石圈薄弱位置，却未出现邻近埃塞俄比亚高原常见的广泛溢流岩浆活动。

研究组通过联合反演面波与接收函数数据，约束该坳陷下方地壳与上地幔地震结构，以评估岩石圈热力学改造程度。在隆升的埃塞俄比亚高原之下普遍存在的厚层下地壳侵入体证据，在正被东非裂谷系统绕避（而非利用）的Anza夭折裂谷下方相对缺失。该坳陷下方的岩石圈地幔仍保留着寒冷、高速的"盖层"特征，与埃塞俄比亚高原形成鲜明对比。Anza裂谷夭折过程中的挥发分耗竭可能使减薄岩石圈呈难熔态且未后期活化。因此，后续裂谷与岩浆活动转而发生在仍具肥沃性质的岩石圈区域——这些区域能够产生熔融并有效降低板块屈服强度。研究表明，岩石圈减薄区域未必都会持续发育重大伸展作用与岩浆省。

附：英文原文

Title: The importance of past rifting in large igneous province development

Author: Kounoudis, R., Bastow, I. D., Ebinger, C. J., Goes, S., Zhou, P., Musila, M., Ogden, C. S., Ayele, A.

Issue&Volume: 2025-11-05

Abstract: Lithospheric thin zones, such as recently failed rifts, are generally assumed to be weak spots where magmatism and deformation can concentrate during rifting and large igneous province development1,2,3. Yet, the Turkana Depression in East Africa, the site of the failed 66-million-year-old Anza Rift, did not experience the widespread flood magmatism seen on the adjacent Ethiopian Plateau, despite being a lithospheric thin spot when the region encountered hot plume material around 45million years ago4. Here we jointly invert surface-wave and receiver function data to constrain crustal and upper-mantle seismic structure below the Depression to evaluate lithospheric thermo-mechanical modification. Evidence for thick lower crustal intrusions, ubiquitous below the uplifted Ethiopian Plateau5,6, is comparatively lacking below the Depression’s failed Anza Rift system, which ongoing East African rifting is circumnavigating, not exploiting. The mantle lithosphere below the Depression has also retained its cool, fast-wavespeed ‘lid’ character, contrasting the Ethiopian Plateau. Volatile depletion during failed Anza rifting probably rendered the thinned lithosphere refractory without later rejuvenation. Subsequent rifting and magmatism thus initiated away from the still-thin Anza Rift, in regions where fertile lithosphere enabled melting and the sufficient lowering of plate yield strength. Areas of thinned lithosphere are thus not necessarily persistent weak zones where significant extension and magmatic provinces will develop.

DOI: 10.1038/s41586-025-09668-7

Source: https://www.nature.com/articles/s41586-025-09668-7