Southwest Pacific Absolute Plate Kinematic Reconstruction Reveals Major Cenozoic Tonga‐Kermadec Slab Dragging

Abstract

Tectonic plates subducting at trenches having strikes oblique to the absolute subducting plate motion undergo trench‐parallel slab motion through the mantle, recently defined as a form of “slab dragging.” We investigate here long‐term slab‐dragging components of the Tonga‐Kermadec subduction system driven by absolute Pacific plate motion. To this end we develop a kinematic restoration of Tonga‐Kermadec Trench motion placed in a mantle reference frame and compare it to tomographically imaged slabs in the mantle. Estimating Tonga‐Kermadec subduction initiation is challenging because another (New Caledonia) subduction zone existed during the Paleogene between the Australia and Pacific plates. We test partitioning of plate convergence across the Paleogene New Caledonia and Tonga‐Kermadec subduction zones against resulting mantle structure and show that most, if not all, Tonga‐Kermadec subduction occurred after ca. 30 Ma. Since then, Tonga‐Kermadec subduction has accommodated 1,700 to 3,500 km of subduction along the southern and northern ends of the trench, respectively. When placed in a mantle reference frame, the predominantly westward directed subduction evolved while the Tonga‐Kermadec Trench underwent ~1,200 km of northward absolute motion. We infer that the entire Tonga‐Kermadec slab was laterally transported through the mantle over 1,200 km. Such slab dragging by the Pacific plate may explain observed deep‐slab deformation and may also have significant effects on surface tectonics, both resulting from the resistance to slab dragging by the viscous mantle.

Reconstruction of Subduction and Back‐Arc Spreading in the NW Pacific and Aleutian Basin: Clues to Causes of Cretaceous and Eocene Plate Reorganizations

“…It would require, however, that the Agattu slab underwent~2,000 km of roll-back from its location of subduction initiation to its modern mantle position. Roll-back of such magnitude may well be possible, but dragging a slab over such a distance through the mantle may be unrealistic-although we note that >1,200 km of slab dragging was recently shown for the Tonga slab (van de Lagemaat et al, 2018). Also, the implied rate of roll-back in our model of~10 cm/year is very high.…”

“…We test our reconstruction against the presence of slabs in the mantle at locations predicted, although we may in places provide different interpretations than van der Meer et al (2018), in the light of our new reconstruction. We assume that, after breakoff from surface plates, slabs sink vertically (Domeier et al, 2016;van der Meer et al, 2010), but that during their subduction they may roll back, or be dragged forward or sideways through the mantle (e.g., Chertova et al, 2014;Funiciello et al, 2008;Schellart et al, 2008;Spakman et al, 2018;van de Lagemaat et al, 2018). We therefore test whether slabs are present in the mantle at locations where our model predicts their break-off, at depths consistent with globally determined sinking rates of~1-2 cm/year (Butterworth et al, 2014;van der Meer et al, 2010van der Meer et al, , 2018.…”

“…Other candidates to have accommodated inception of Pacific subduction around 50 Ma is subduction initiation at the Izu-Bonin-Marianas Trench (Faccenna et al, 2012;Ishizuka et al, 2011;Seton et al, 2015) and the Tonga-Kermadec Trench (e.g., Sutherland et al, 2017). However, as there was only very minor Pacific-Australia convergence before 45 Ma, and most if not all such convergence was accommodated at the New Caledonia-Northland subduction zone between the modern Tonga Trench and Australia until 30 Ma Tonga-Kermadec subduction initiation is kinematically quite unlikely to have happened long before 30 Ma (van de Lagemaat et al, 2018). Subduction initiation at the Izu-Bonin-Marianas Trench is widely considered to have started simultaneously with the inception of forearc spreading at 51 Ma (Ishizuka et al, 2011), but this critically hinges on the assumption that subduction initiation was a spontaneous event (Arculus et al, 2015;Stern, 2004;Stern et al, 2012).…”

The Dynamic History of 220 Million Years of Subduction Below Mexico: A Correlation Between Slab Geometry and Overriding Plate Deformation Based on Geology, Paleomagnetism, and Seismic Tomography

“…From Figure it follows that since 190 Ma, the Vizcaíno Peninsula (now at ~28°N) has been between 25°N and 35°N, implying that correlating the Mexican geological subduction records to mantle structure at these same latitudes is warranted. In Late Triassic to Early Jurassic time, the North American Plate moved ~15° to the north relative to the mantle (Figure ), which may imply that the oldest, Upper Triassic geological records of subduction (at the North American Plate) may be offset relative to deep mantle structure by such a distance, assuming that the slab did not undergo lateral dragging (Spakman et al, ), which may offset slabs relative to their initial position of subduction laterally by >10° (Van de Lagemaat et al, ). We also note that the TPW calculations of Steinberger and Torsvik () and Torsvik et al () include a mantle‐fixed TPW‐Euler pole that pierces through the centers of mass of the Large Low Shear wave Velocity Provinces at the core‐mantle boundary.…”

Control of Subduction Zone Age and Size on Flat Slab Subduction

“…But the spatial correlation between ridge/plateau subduction and flat slab subduction has many exceptions, with regions of aseismic ridge subduction lacking flat slab subduction (e.g., Tonga with Louisville Ridge, New Hebrides with d'Entrecasteaux Ridge, Mariana with Marcus-Necker Ridge, Kamchatka with Emperor Ridge) and some flat slab subduction segments lacking an aseismic ridge/plateau (e.g., Mexico) Clayton, 2011, 2013;Manea et al, 2017). Others have proposed that flat slab subduction might result from forced trench retreat (e.g., van Hunen et al, 2004;Schepers et al, 2017), strong suction forces in the mantle wedge (e.g., Tovish et al, 1978), or slab-plume interaction (e.g., Betts et al, 2009). The latter mechanism has not generally been applied to Cenozoic examples of flat slab subduction, and recent geodynamic models of slabplume interaction for present-day Earth-like settings indicate that plumes generally do not affect slab geometry as their upward buoyancy flux can be more than two orders of magnitude smaller than the downward slab buoyancy flux (Mériaux et al, 2016).…”