Maximum size and distribution in time and space of mantle plumes: evidence from large igneous provinces

Our recently published database of 304 possible large igneous provinces (LIPs) extending back to 3.8 Ga is used to explore the maximum size and distribution in time and space of large mantle plume heads. Maximum plume head size has been estimated using various techniques for two of the largest continental LIPs, the 1.27 Ga Mackenzie, and 0.20 Ga CAMP events, as well as two of the largest oceanic LIPs, Ontong Java and Manihiki. Each is consistent with an underlying flattened plume head radius of about 1000 km, a value considered normal for a plume rising from the deep mantle, and suggesting that even plumes associated with major mantle upwellings are normal size. The LIP record is semi-continuous back to at least 3.0 Ga, and there is no obvious periodicity, indicating that plume activity is probably not cyclic. Apparent increases in plume activity between 0.15 Ga and present, and perhaps, between 2.8 and 2.7 Ga, can be explained by increased preservation of oceanic LIPs. Clusters of plumes in time and space are common in the LIP record. At 6 times since 1.3 Ga, multiple LIPs whose ages span 10 Myr or less are linked to more than one plume centre. At an additional 37 times since 3.0 Ga, LIPs are found on more than one continental block and may represent multiple plumes. However, better-constrained continental reconstructions are required in order to determine which of these are due to a single plume and which require more than one plume. Some synchronous plume centers are clustered regionally suggesting a common mantle perturbation at depth while others are widely separated and, if genetically linked, would imply a global core-mantle event. In addition, some regional clusters of LIPs show a range in age greater than 10 Myr. However, in most such cases it is unknown whether these represent linked events or whether they are random associations in a dense age spectrum of LIPs. Crown Copyright (C) 2002 Published by Elsevier Science Ltd. All rights reserved.