Temporal Evolution of the Swell and Magmatic Fluxes Along the Louisville Hotspot Chain

Adam, Claudia; Smith, Madison N.; Kempton, Pamela D.; Brueseke, Matthew E.

doi:10.1029/2022gc010568

Cited by 2 publications

(1 citation statement)

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“…Data from hotspots not included in the above study, such as Amsterdam St Paul (∼6 Myr; Maia et al 2011;Sibrant et al 2019) andIceland (∼8 Myr, Parnell-Turner et al 2014), also show evidence of similar periods of melt flux variability. Additionally, Adam et al, 2022 suggest that ∼5-10 Myr signals observed from estimates of magmatic and swell flux variations at the Louisville hotspot are likely caused by shallow phenomena, in particular to instabilities within tilted plume conduits.…”

Section: Plume Periodicity and Viscosity Ratiomentioning

confidence: 96%

Temporal variations in plume flux: characterizing pulsations from tilted plume conduits in a rheologically complex mantle

Neuharth

Mittelstaedt

2022

Geophysical Journal International

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Summary Along age-progressive hotspot volcano chains, the emplacement rate of igneous material varies through time. Time-series analysis of changing emplacement rates at a range of hotspots finds that these rates vary regularly at periods of a few to several tens of millions of years, indicative of changing melt production within underlying mantle plumes. Many hotspots exhibit at least one period between ∼2–10 Myr, consistent with several proposed mechanisms for changing near-surface plume flux, and thus melting rate, such as small-scale convection, solitary waves, and instability formation in tilted plume conduits. Here, we focus on quantifying instability growth within plumes tilted by overlying plate motion. Previous studies using fluids with constant or temperature-dependent viscosity suggest that such instabilities should not form under mantle conditions. To test this assertion, we use a modified version of the finite element code ASPECT to simulate 400 million years of evolution of a whole-depth mantle plume rising through the transition zone and spreading beneath a moving plate. In a two-dimensional spherical shell geometry, ASPECT solves the conservation equations for a compressible mantle with a thermodynamically consistent treatment of phase changes in the mantle transition zone and subject to either a temperature-, and depth-dependent linear rheology or a temperature-, depth-, and strain-rate dependent non-linear rheology. Additionally, we examine plume evolution in a mantle subject to a range of Clapeyron slopes for the 410 km (1 to 4 MPa/K) phase transitions. Results suggest that plume conduits tilted by > 67° become unstable and develop instabilities that lead to initial pulses in the transition zone followed by repeated plume pulsing in the uppermost mantle. In these cases, pulse size and frequency depend strongly on the viscosity ratio between the plume and ambient upper mantle. Based upon our results and comparison with other studies, we find that the range of statistically significant periods of plume pulsing in our models (∼2–6 Myr), the predicted increase in melt flux due to each pulse (5–15 × 10−4 km3 km−1 yr−1), and the time estimated for a plume to tilt beyond 67° in the upper mantle (10–50 Myr) are consistent with observations at numerous hotspot tracks across the globe. We suggest that pulsing due to destabilization of tilted plume conduits may be one of several mechanisms responsible for modulating the melting rate of mantle plumes as they spread beneath the moving lithosphere.

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Section: Plume Periodicity and Viscosity Ratiomentioning

confidence: 96%