Pacific plate slab pull and intraplate deformation in the early Cenozoic

Abstract

Abstract. Large tectonic plates are known to be susceptible to internal deformation, leading to a range of phenomena including intraplate volcanism. However, the space and time dependence of intraplate deformation and its relationship with changing plate boundary configurations, subducting slab geometries, and absolute plate motion is poorly understood. We utilise a buoyancy-driven Stokes flow solver, BEM-Earth, to investigate the contribution of subducting slabs through time on Pacific plate motion and plate-scale deformation, and how this is linked to intraplate volcanism. We produce a series of geodynamic models from 62 to 42 Ma in which the plates are driven by the attached subducting slabs and mantle drag/suction forces. We compare our modelled intraplate deformation history with those types of intraplate volcanism that lack a clear age progression. Our models suggest that changes in Cenozoic subduction zone topology caused intraplate deformation to trigger volcanism along several linear seafloor structures, mostly by reactivation of existing seamount chains, but occasionally creating new volcanic chains on crust weakened by fracture zones and extinct ridges. Around 55 Ma, subduction of the PacificIzanagi ridge reconfigured the major tectonic forces acting on the plate by replacing ridge push with slab pull along its northwestern perimeter, causing lithospheric extension along pre-existing weaknesses. Large-scale deformation observed in the models coincides with the seamount chains of Hawaii, Louisville, Tokelau and Gilbert during our modelled time period of 62 to 42 Ma. We suggest that extensional stresses between 72 and 52 Ma are the likely cause of large parts of the formation of the Gilbert chain and that localised extension between 62 and 42 Ma could cause late-stage volcanism along the Musicians volcanic ridges. Our models demonstrate that early Cenozoic changes in Pacific plate driving forces only cause relatively minor changes in Pacific absolute plate motion directions, and cannot be responsible for the Hawaiian-Emperor bend (HEB), confirming previous interpretations that the 47 Ma HEB does not primarily reflect an absolute plate motion event.

Pacific plate motion change caused the Hawaiian-Emperor Bend

“…In our exercise (Fig. 3a), the Hawaiian hotspot drifts ∼1,800 km to the west in addition to ∼1,000 km to the south, which is in good qualitative agreement with the estimates of hotspot drift inferred from kinematic models that do not feature a prominent change in the Pacific plate motion around the time of the bend242627 (Fig. 4, see Methods).…”

“…4 were obtained by reconstructing the eruption sites of radiometrically dated seamounts of the Hawaiian-Emperor Chain (Fig. 1) using finite rotations describing the motions of the Pacific plate in three absolute reference frames242739 that do not feature prominent directional changes of the Pacific plate motion at the time of the formation of the HEB (47 Ma); see the caption of Fig. 4 for the sources for these reference frames.…”

“…(WK08-D). ( b ) The geodynamic APM model of Butterworth et al 24. (42–72 Myr ago), augmented by the rotations from Wessel and Kroenke52 (WK08-A) for the younger ages, and extrapolated to 83 Ma as in Wessel & Müller53.…”

“…The idea that the hotspot was mobile during this time interval has been generally accepted by the geoscientific community, although with some dissenting voices10. Most geodynamic models also predict a drift of the hotspot to the south, and several recent studies argue that a rapid southward motion of the Hawaiian hotspot that ceased at ∼47 Ma can explain the formation of the HEB without requiring a significant change in the Pacific plate motion around that time12142324.…”

Ridge‐spotting: A new test for Pacific absolute plate motion models

“…Our new method will be tested using a representative mix of published APM models. Specifically, we have selected the two fixed hot spot models DC85 [ Duncan and Clague , ] and WK08A [ Wessel and Kroenke , ], a partially fixed hot spot model (WK08D) that allows just the Hawaii hot spot to migrate rapidly during the Emperor stage so that no HEB is predicted [ Chandler et al ., ], a moving hot spot model (OMS05) determined for the Indo‐Atlantic realm but projected into the Pacific via the Africa‐India‐Antarctica‐Pacific plate circuit [ O'Neill et al ., ], a global moving hot spot model (D2012) fitting five prominent hot spot chains from the world's major ocean basins [ Doubrovine et al ., ], and finally an APM model (B2014) not obtained by fitting seafloor data but predicted by geodynamic modeling of slab pull and ridge push [ Butterworth et al ., ]. Because our study is restricted to examining crustal seafloor ages and locations only, the hot spot locations needed to establish some of the above APM models are not required.…”