Plume‐Induced Sinking of Intracontinental Lithospheric Mantle: An Overlooked Mechanism of Subduction Initiation?

Abstract

Although many different mechanisms for subduction initiation have been proposed, only few of them are viable in terms of consistency with observations and reproducibility in numerical experiments. In particular, it has recently been demonstrated that intra‐oceanic subduction triggered by an upwelling mantle plume could greatly contribute to the onset and operation of plate tectonics in the early and, to a lesser degree, modern Earth. On the contrary, the initiation of intra‐continental subduction still remains underappreciated. Here we provide an overview of 1) observational evidence for upwelling of hot mantle material flanked by downgoing proto‐slabs of sinking continental mantle lithosphere, and 2) previously published and new numerical models of plume‐induced subduction initiation. Numerical modeling shows that under the condition of a sufficiently thick (>100 km) continental plate, incipient downthrusting at the level of the lowermost lithospheric mantle can be triggered by plume anomalies of moderate temperatures and without significant strain‐ and/or melt‐related weakening of overlying rocks. This finding is in contrast with the requirements for plume‐induced subduction initiation within oceanic or thinner continental lithosphere. As a result, plume‐lithosphere interactions within continental interiors of Paleozoic‐Proterozoic‐(Archean) platforms are the least demanding (and thus potentially very common) mechanism for initiation of subduction‐like foundering in the Phanerozoic Earth. Our findings are supported by a growing body of new geophysical data collected in various intra‐continental areas. A better understanding of the role of intra‐continental mantle downthrusting and foundering in global plate tectonics and, particularly, in the initiation of “classic” ocean‐continent subduction will benefit from more detailed follow‐up investigations.

Connection Between a Subcontinental Plume and the Mid‐Lithospheric Discontinuity Leads to Fast and Intense Craton Lithospheric Thinning

“…Subduction-and plume-induced lithospheric thinning could also be intrinsically linked. While the causes of subduction initiation remain highly debated (e.g., Stern & Gerya, 2018), plume-lithosphere interaction within thick continents has been suggested to be the least demanding mechanism to initiate subduction during the Phanerozoic (Cloetingh et al, 2021). Continental lithospheric thinning and delamination can potentially occur during plume-lithosphere interaction, with downthrusting of the lowermost lithospheric mantle finally leading to subduction initiation (Cloetingh et al, 2021).…”

“…While the causes of subduction initiation remain highly debated (e.g., Stern & Gerya, 2018), plume-lithosphere interaction within thick continents has been suggested to be the least demanding mechanism to initiate subduction during the Phanerozoic (Cloetingh et al, 2021). Continental lithospheric thinning and delamination can potentially occur during plume-lithosphere interaction, with downthrusting of the lowermost lithospheric mantle finally leading to subduction initiation (Cloetingh et al, 2021). There is some evidence that could imply the existence of mantle downwelling in intra-continental settings (Cloetingh et al, 2021 and references therein), for example, beneath the Caucasus Mountains at the intersection of the Europe and Asia, or the Tianshan orogenic belt in the northwest China.…”

“…Continental lithospheric thinning and delamination can potentially occur during plume-lithosphere interaction, with downthrusting of the lowermost lithospheric mantle finally leading to subduction initiation (Cloetingh et al, 2021). There is some evidence that could imply the existence of mantle downwelling in intra-continental settings (Cloetingh et al, 2021 and references therein), for example, beneath the Caucasus Mountains at the intersection of the Europe and Asia, or the Tianshan orogenic belt in the northwest China. Therefore, after plume-induced lithospheric thinning, subsequent subduction could occur that further enhances the lithospheric thinning process.…”

Plume-Induced Subduction Initiation: Revisiting Models and Observations

“…Numerical and observational evidence have shown that sinking of lithosphere into mantle induced by plume head is irrelevant to the nature of the overlying plate, it can be oceanic or continental lithosphere (e.g., Ueda et al, 2008;Burov and Cloetingh, 2009;Burov and Cloetingh, 2010;Gerya et al, 2015). Plume-induced sinking of intracontinental lithospheric mantle has been reviewed by Cloetingh et al (2021). Here, we focus on plume-induced oceanic subduction initiation and briefly revisit plume-induced sinking of intracontinental lithospheric mantle.…”

Microcontinent subduction and S-type volcanism prior to India–Asia collision

“…Besides, thermomechanical study reveals that the thermal and buoyancy effects of mantle plume impingement on the bottom of the continental part of a subducting plate can also induce the separation of microcontinents from the main body of the continent 59 . With the initiation of the northward subduction of the Neo-Tethys crust in early Mesozoic 60 , possibly induced by the impingement of mantle plume at the transition zone between oceanic and continental lithosphere 61 , these microcontinents are thought to have accreted to the Lhasa block along the IYSZ in the early Cenozoic, similar to the Burma terrane 62 and the Oaxaquia in North America 63 . However, no geological records have been reported to document the accretion in the IYSZ.…”