Quantifying Periodic Variations in Hotspot Melt Production

• Published in: Journal of geophysical research. Solid earth 2021-07, Vol.126 (7), p.n/a
• Main Authors: Morrow, T. A., Mittelstaedt, E. L.
• Format: Article
• Language: English
• Subjects: Anomalies; Chains; Chemical reactions; Dynamics; Earth; Earth mantle; Elastic plates; Entrainment; Flexing; flexure; Fluctuations; Flux; Geophysics; gravity; Gravity anomalies; Heterogeneity; Hot spots; Hot spots (geology); hotspot; Lithosphere; Mantle plumes; Ocean basins; Ocean circulation; Ocean floor; Oceanic crust; Oceans; Periodic variations; Periodicities; plume; Plumes; Rheological properties; Seamounts; Spectral analysis; Spectral methods; Spectrum analysis; Statistical analysis; Upper mantle; Upwelling; Variation
• ISSN: 2169-9313; 2169-9356
• DOI: 10.1029/2021JB021726

Fluctuations in estimated mantle plume melt production rates suggest complex dynamics in the upper mantle including changes in plume upwelling, compositional heterogeneity within plume stems, entrainment of anomalous mantle, or other processes. Despite the implications for mantle dynamics, differences between previous studies including the methods, study areas, and types of melt volumes estimated, limit inter‐hotspot comparisons and assessment of global variability. Here, we use a consistent methodology to calculate igneous melt production through time across a suite of 12 hotspot chains located in the Pacific, Indian, and Atlantic Ocean basins. Using global data sets of topography, gravity, sediment cover, and seafloor age along with spectral methods for calculating elastic plate flexure and gravity anomalies, we estimate the total volume of igneous material at each hotspot in three components: (a) volcanic edifices, (b) flexural infill, and (c) intrusions (underplating) within the upper mantle and lower crust. Results indicate time‐averaged melt production rates across all studied hotspots range from 3.44 m3 s−1 (Cobb) to 14.75 m3 s−1 (Kerguelen), with underplating making up the largest component. Through time, melt production rates vary from 0.1 to 2.5 times average values with statistically significant periodic fluctuations of 1.1–71.5 Myr. Spectral analysis of estimated melt volumes shows total melt production varies periodically at all 12 hotspots. Excepting Galápagos, the studied hotspots exhibit multiple periodicities of melt production variability, implying complex dynamic, thermal, and/or chemical processes within the plume conduit. Moreover, we find several groups of hotspots exhibiting similar periods of melt production variability. Plain Language Summary Mantle plumes are buoyant, ascending columns of material from deep within the Earth’s mantle. The rate of ascent and volume flux of material ascending in a mantle plume is thought to vary over time, due to rheologic conditions inside the Earth or complex fluid dynamic interactions in the rising column of material. When a mantle plume reaches the surface of the planet, plume‐derived partial melts are extracted onto the surface or emplaced in the brittle lithosphere in the form of seamounts and ocean islands, forming a quasi‐linear chain of volcanic material known as a hotspot. However, the influence of variations in plume flux on the amount of melt produced at hotspots is poorly understood. Her