Evidence and implications for a widespread magmatic shutdown for 250 My on Earth

Analysis of the global distribution of U/Pb ages of both subduction-related granitoids and of detrital zircons suggests that a widespread reduction in magmatic activity on Earth beginning about 2.45 Ga and lasting for 200-250 My. There are no arc-type greenstones or tonalite-trondhjemite-granodiorite (TTG) suites and only one large igneous province (LIP) reported in this time window. There is little Nd or Hf isotopic evidence to support significant additions to the continental crust at convergent plate margins between 2.45 and 2.2 Ga. Also during this time, there are major unconformities on most cratons and a gap in deposition of banded iron formation (BIF), both consistent with a major drop in sea level. Oxygenation of the atmosphere at: 2.4 Ga followed by widespread glaciation at 2.4-2.3 Ga also may be related to the initiation of the global magmatic lull. We suggest that an episodic mantle thermal regime, during which a large part of the plate circuit effectively stagnates, may explain the 250-My magmatic age gap on Earth and a remarkable feature of the Paleoproterozoic record. (C) 2009 Elsevier B.V. All rights reserved.