Mantle Transition Zone Receiver Functions for Bermuda: Automation, Quality Control, and Interpretation

Abstract

Intraplate, or hot-spot, volcanism is typically interpreted as the result of plate motion over a spatially localized region of long-lived deep-mantle upwelling (Morgan, 1971). Arguably the most famous example of this process is the Hawaiian-Emperor Seamount Chain (e.g., Steinberger et al., 2004). Whether Bermuda belongs in this category of an intraplate volcano originating from a deep-mantle plume source remains uncertain. The island of Bermuda, situated atop a roughly 10 6 km 2 bathymetric swell in the Western Atlantic Ocean (Figure 1), lacks an age-progressive seamount chain and present-day active volcanism. Radiometric dating of borehole samples from the island and adjacent swell area revealed that the volcanic pedestal was formed during the Middle Eocene (ca. 48-45 Ma), and reached subaerial extent in the Late Eocene, approximately 40-36 Ma (Vogt & Jung, 2007). The pedestal has remained volcanically dormant since, and is now overlain by a fossiliferous carbonate platform. In spite of these facts, which suggest an isolated volcanic episode leading to Bermuda's formation, the region is included in some plume-hot-spot catalogs (King & Adam, 2014; Sleep, 1990), though it fails to meet others' definitions of a mantle plume (Courtillot et al., 2003) due to its lack of a hotspot track and weak evidence for a significant upper mantle low velocity anomaly from seismic tomography. Additionally, several studies suggest a link between the igneous activity which formed Bermuda and other volcanic events, such as the formation of the Mississippi Embayment (Cox & Van Arsdale, 2002; L. Liu et al., 2017) and the reactivation of the New Madrid rift system (Chu et al., 2013), though it may not be linked to all the magmatism along its purported track (Mazza et al., 2014). Recent work in whole mantle seismic tomographic imaging has facilitated the observation and interpretation of several of these deep-mantle plume structures (e.g., French & Romanowicz, 2015), particularly in association with the Pacific and African LLSVPs (Lekić et al., 2012). The presence of a strong, high temperature mantle upwelling should be visible in tomographic images of mantle velocity. To explore this hypothesis in the context of Bermuda, we made cross sections through two seismic tomography models (Figure 2), the joint P and S velocity model LLNL_G3D_JPS (Simmons et al., 2015) and the radially anisotropic S velocity model SEMUCB_WM1 (French & Romanowicz, 2014). Both models display a low velocity anomaly beneath Bermuda relative to the one-dimensional (1-D) average velocity of the profile interrogated. This anomaly extends as a continuous feature to roughly 1,500 km depth, and then is deflected eastward

Improving Constraints on Planetary Interiors With PPs Receiver Functions

“…In principle, an ideal RF represents the impulse response due to structure directly beneath a seismic station, because signature of the source and source‐side structure is removed through deconvolution (e.g., Ammon, 1991). Thus, unlike many other seismic methodologies that require a network of seismometers, RF analysis can extract useful structural constraints even when a single three component seismic station is available (e.g., Burky et al., 2021; Kim and Lekić, 2019; Panning et al., 2017). Extraction of rich information contained in RFs at a single station can be achieved by incorporating many independent measurements from both Ps ‐RFs and the corresponding free‐surface reverberations contained in the same record.…”

Seismic evidence for a 1000 km mantle discontinuity under the Pacific

“…The variable mantle transition zone thickness is interpreted, within the context of mineralogical composition 13,14 , as sensitive to temperature differences from the ambient mantle 8 . Using average mantle properties and published estimates for the relevant Clapeyron slopes 15 , a 100 K temperature increase implies a ~15 km thinning of the mantle transition zone (hereafter: MTZ).…”

Data-space cross-validation of global tomographic models to assess mantle structure underneath the Pacific Ocean

“…(IV) Can mantle plumes that rise from broad upwelling regions anchored at the CMB, as is apparently the case beneath Marquesas (Lei et al 2020;French & Romanowicz 2015), stall in the lower mantle? (V) Do some hotspots originate from within or just below the mantle transition zone (Benoit et al 2013;Burky et al 2021), as suggested by the structure beneath Tahiti and Louisville, or does that reflect a lack of resolution? Does the Large Low Shear-Velocity Province at the CMB beneath Samoa and Tahiti give rise to multiple plume conduits (Garnero et al 2016), as beneath La Réunion (Wamba et al 2023)?…”