LIP formation and protracted lower mantle upwelling induced by rifting and delamination

Abstract

Large Igneous Provinces (LIPs) are commonly attributed to mantle plumes, hot upwellings from the deep lower mantle, apparently unrelated to plate motions. However, LIPs often form in association with rifting and breakup. Using numerical modelling, we introduce a novel idea that explains plume-like mantle upwelling by plate tectonic processes. Our model indicates that rifting-induced delamination of orogenic lithosphere can perturb the thermochemical mantle stratification and induce lower mantle upwelling which causes syn-rift LIP formation followed by protracted and enhanced mid ocean ridge basalt (MORB) generation. Our model provides an explanation for the geographical correlation between the Caledonian suture, the North Atlantic Igneous Province (NAIP) and present-day Icelandic magmatism.

Publisher’s Note

“…To date, there has been limited discussion of whether the rifting process in itself can account for the excess volcanism observed (Peace et al, 2017a). This is likely partly because there has been relatively little attention paid to modelling the volumes, and ranges in volume, of melt observed (Petersen et al, 2018). Where this has been done, the results are compelling.…”

“…A unifying genetic model must account for this variable spatiotemporal distribution (Lundin and Doré, 2005b;Peace et al, 2017a). Petersen et al (2018) recently proposed a mechanism to explain the two-phase igneous activity associated with the NAIP based on numerical modelling. They propose that lithospheric delamination triggered by destabilisation of thickened and metamorphosed, highdensity lower crust produced the first igneous peak by small scale convection induced by detachment of the lithosphere.…”

“…In addition, much previous work links continental rifts and breakup on a range of scales and tectonic environments to pre-existing structures (Wu et al, 2016;Petersen and Schiffer, 2016; Peace et al, 2018b;Schiffer et al, 2018;Collanega et al, 2019;Schiffer et al, this volume). A link between the intersection of propagating rifts with pre-existing suture zones and the production of magmatism has been suggested based primarily on geological observations from Atlantic margins and numerical modelling (Koopmann et al, 2014a;Schiffer et al, 2015;Peace et al, 2017a;Petersen et al, 2018). In these models, a barrier to rift propagation results in excess magmatism by blocking and diverting mantle flow beneath a propagating rift axis.…”

“…1). The processes that initiate the dispersal of these large continental accumulations remain controversial (Santosh et al, 2009;Audet and Bürgmann, 2011;Murphy and Nance, 2013;Nance et al, 2014;Petersen and Schiffer, 2016;Peace et al, 2017a;Petersen et al, 2018;Schiffer et al, 2018;Olierook et al, 2019). The debate primarily revolves around whether continental dispersal is driven by deep-rooted thermal anomalies (Morgan-type mantle plumes) or shallow plate tectonic processes (Storey, 1995;Dalziel et al, 2000;Beutel et al, 2005;Frizon De Lamotte et al, 2015;Pirajno and Santosh, 2015;Yeh and Shellnutt, 2016;Keppie, 2016;Petersen et al, 2018;Heron, 2018).…”

Structural inheritance in the North Atlantic

“…Despite the often-proposed deep, active, buoyant upwellings beneath the CNAR, factors like the thermal state and composition of the crust and mantle, small-scale convection, upwelling, volatile content, and general, pre-existing (inherited) lithospheric and crustal structure may play major roles in the magmatic and tectonic evolution (e.g. King and Anderson 1998;Asimow and Langmuir 2003;Korenaga 2004;Foulger et al , 2019Meyer et al 2007;Simon et al 2009;Hole and Millett 2016;Petersen et al 2018;Hole and Natland 2019).…”