Keel of the eastern North China craton weakened by Proterozoic large igneous provinces

Abstract

ABSTRACT Cratons are the most mature parts of the continents on Earth and can remain stable for billions of years. Cratonic keels may be destroyed, for which a prime example is the eastern North China craton (NCC), which was removed during the Mesozoic. However, the critical stable state of the keel and the destroying mechanism of the rigid and buoyant cratonic roots remain enigmatic. Here, rhenium-osmium and neodymium isotope datasets from the eastern NCC open up a possible approach to reveal its evolution prior to the destruction. Two Re (rhenium) -depletion model age peaks of the peridotite xenoliths entrained by Phanerozoic basalts reconcile the ages of the large igneous provinces (LIPs) of Yanliao (ca. 1.3 Ga) and Xuhuai (ca. 0.92 Ga), respectively. This indicates that the mantle lithosphere of the eastern NCC has undergone metasomatism and growth during the emplacement of the two LIPs. The Proterozoic LIPs probably produced buoyant mantle residues that were then captured beneath thinned lithosphere regions. Such igneous processes occur at a depth of ~100 km and may induce the formation of weak zones (e.g. palaeo-mid-lithosphere discontinuity) partially within the rigid mantle lithosphere. The palaeo-weak zones might be rheologically unstable structures and probably reduced the stability of the craton, presenting as foci for potential later keel destruction. This provides evidence that LIP event may be another key factor for the intra-cratonic mantle lithosphere destruction.