Continental Magmatism: The Surface Manifestation of Dynamic Interactions Between Cratonic Lithosphere, Mantle Plumes and Edge‐Driven Convection

Abstract

Several of Earth's intra‐plate volcanic provinces lie on or adjacent to continental lithosphere. Although many are believed to mark the surface expression of mantle plumes, our limited understanding of how buoyant plumes interact with heterogeneous continental lithosphere prevents further progress in identifying mechanisms at the root of continental volcanism. In this study, using a suite of 3‐D geodynamical models, we demonstrate that the magmatic expression of plumes in continental settings is complex and strongly sensitive to the location of plume impingement, differing substantially from that expected beneath more homogeneous oceanic lithosphere. Within Earth's continents, thick cratonic roots locally limit decompression melting. However, they deflect plume conduits during their ascent, with plume material channeled along gradients in lithospheric thickness, activating magmatism away from the plume conduit, sometimes simultaneously at locations more than a thousand kilometres apart. This magmatism regularly concentrates at lithospheric steps, where it may be difficult to distinguish from that arising through edge‐driven convection. At times, the flow field associated with the plume enhances melting at these steps long before plume material enters the melting zone, implying that differentiating geochemical signatures will be absent. Beneath regions of thinner lithosphere, plume‐related flow can force material downwards at lithospheric steps, shutting off pre‐existing edge‐related magmatism. Additionally, variations in lithospheric structure can induce internal destabilization of ponding plume material, driving intricate magmatic patterns at the surface. Our analysis highlights the challenges associated with linking continental magmatism to underlying mantle dynamics, motivating an inter‐disciplinary approach in future studies.

Mantle Plume‐Lithosphere Interactions Beneath the Emeishan Large Igneous Province

“…Yet, regardless of the process that produced a shallow LAB beneath and around the INZ, it is likely that such lithospheric structure influenced asthenospheric dynamics by acting as a focus point for subsequent mantle upwellings (Duvernay et al., 2022). The deep high‐temperature anomaly (>1400°C) in profile B‐B’ (Figure 3) shows evidence of large‐scale mantle upwelling that is focused by thin lithosphere beneath southwestern ELIP.…”

Coupled Geodynamical‐Geochemical Perspectives on the Generation and Composition of Mid‐Ocean Ridge Basalts

“…Specifically, their database includes starting compositions that deviate from fertile mantle peridotites (Hirschmann, 2000;McDonough & Sun, 1995), such as HK-66 (Hirose & Kushiro, 1993) and PHN-1611(Kushiro, 1996, which likely shift isobaric melt productivity curves toward lower temperatures before clinopyroxene exhaustion (Figure 1; Hirschmann, 2000). Such a change in peridotite solidus and, thus, in the pressure-temperature conditions at which the first few per cent of melting occur can substantially affect melt volume predictions in geologic settings where only low-degree partial melting takes place, such as certain intra-plate volcanic regions (Ball et al, 2019;Duvernay et al, 2021Duvernay et al, , 2022; investigating this effect will be the focus of a later study.…”

Lithospheric structure and melting processes in southeast Australia: new constraints from joint probabilistic inversions of 3D magnetotelluric and seismic data

“…If EDC/SDU cells are the main driver for the leucitite volcanism, they need to be able to produce melts for a relatively short period of time (non regenerative) to explain the punctuated nature of this volcanism. Indeed, numerical simulations clearly show that ED/SD instabilities are ephemeral in nature and can be hindered by small perturbations in the sublithospheric flow (e.g., King & Anderson, 1995;Duvernay et al, 2021bDuvernay et al, , 2022.…”

“…The presence of an anomalously hot upwelling or plume can also enhance or shut down melting near lithospheric steps (Mather et al, 2020;Duvernay et al, 2022), making it difficult to separate the two mechanisms without further knowledge on the underlying mantle dynamics. Thus, while our results provide a firm ground for interpretations on the origin of the EAVP and the roles that lithospheric structure and composition played, we cannot assess the deep mantle processes that controlled the large-scale sublithospheric flow.…”