1. Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA

Correspondence to: Shu-Chuan Lin¹ Correspondence and requests for materials should be addressed to S. C. L. (Email: skylin@umich.edu).

Abstract

The hypothesis that a single mushroom-like mantle plume head can generate a large igneous province within a few million years has been widely accepted¹. The Siberian Traps at the Permian–Triassic boundary² and the Deccan Traps at the Cretaceous–Tertiary boundary³ were probably erupted within one million years. These large eruptions have been linked to mass extinctions. But recent geochronological data^{4, 5, 6, 7, 8, 9, 10, 11} reveal more than one pulse of major eruptions with diverse magma flux within several flood basalts extending over tens of million years. This observation indicates that the processes leading to large igneous provinces are more complicated than the purely thermal, single-stage plume model suggests. Here we present numerical experiments to demonstrate that the entrainment of a dense eclogite-derived material at the base of the mantle by thermal plumes can develop secondary instabilities due to the interaction between thermal and compositional buoyancy forces. The characteristic timescales of the development of the secondary instabilities and the variation of the plume strength are compatible with the observations. Such a process may contribute to multiple episodes of large igneous provinces.

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