Abstract
Controversy surrounds the fixity of both hotspots and large low shear velocity provinces (LLSVPs). Paleomagnetism, plate-circuit analyses, sediment facies, geodynamic modeling, and geochemistry suggest motion of the Hawaiian plume in Earth’s mantle during formation of the Emperor seamounts. Herein, we report new paleomagnetic data from the Hawaiian chain (Midway Atoll) that indicate the Hawaiian plume arrived at its current latitude by 28 Ma. A dramatic decrease in distance between Hawaiian-Emperor and Louisville chain seamounts between 63 and 52 Ma confirms a high rate of southward Hawaiian hotspot drift (~47 mm yr−1), and excludes true polar wander as a relevant factor. These findings further indicate that the Hawaiian-Emperor chain bend morphology was caused by hotspot motion, not plate motion. Rapid plume motion was likely produced by ridge-plume interaction and deeper influence of the Pacific LLSVP. When compared to plate circuit predictions, the Midway data suggest ~13 mm yr−1 of African LLSVP motion since the Oligocene. LLSVP upwellings are not fixed, but also wander as they attract plumes and are shaped by deep mantle convection.
Highlights
Controversy surrounds the fixity of both hotspots and large low shear velocity provinces (LLSVPs)
Geodynamic modeling of the entrainment and advection of a mantle plume conduit in mantle convection suggested southward Hawaiian hotspot motion[5,12]. This class of model tends to underestimate the latitudinal motion relative to that recorded by the Emperor seamount paleomagnetic data, and requires a change in plate motion to create the ~60° Hawaiian-Emperor Bend (HEB)[1], points we return to below
When combined with other global observations, these analyses indicate that LLSVPs are not fixed, but drift as they are affected by lower mantle flow
Summary
Controversy surrounds the fixity of both hotspots and large low shear velocity provinces (LLSVPs). Hotspot tracks on oceanic plates outside the Pacific Ocean basin had long been used to predict the trend of volcanic edifices emanating from the Hawaiian hotspot if it had been fixed[2] These non-Pacific hotspots must be tied to the Pacific plate via a plate circuit: a continuous linkage of plates separated only by spreading boundaries, with a history that can be reconstructed using marine magnetic anomalies. Geodynamic modeling of the entrainment and advection of a mantle plume conduit in mantle convection suggested southward Hawaiian hotspot motion[5,12] This class of model tends to underestimate the latitudinal motion relative to that recorded by the Emperor seamount paleomagnetic data, and requires a change in plate motion to create the ~60° Hawaiian-Emperor Bend (HEB)[1], points we return to below. Torsvik et al.[17] argue that Emperor paleomagnetic data could be anomalous because of non-dipole fields, quoting results from Hawaiian lavas of the last ~425 kyr (HSDP2)[18], which show an apþpa1r8e:n0t À12:9
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