Evidence for slab material under Greenland and links to Cretaceous High Arctic magmatism

Shephard, Grace E.; Trønnes, Reidar G.; Spakman, Wim; Panet, I.; Gaina, Carmen

doi:10.1002/2016gl068424

Cited by 18 publications

(25 citation statements)

References 56 publications

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“…Also, the low-Vp zone beneath western Svalbard seems to be interrupted at depths of 460-610 km. Between 1,050 and 1,500 km depths beneath southwestern Greenland, we do not observe any large velocity anomalies, although many existing global tomography models (e.g., Ritsema et al, 2011;Simmons et al, 2010) show a common high-V region that has been interpreted as a subducted slab (Shephard et al, 2016). Toyokuni et al (2020) also revealed a high-Vp anomaly in the same region.…”

Section: Results Of Different Tomographic Inversionscontrasting

confidence: 56%

P Wave Tomography Beneath Greenland and Surrounding Regions: 1. Crust and Upper Mantle

2020

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We study the 3-D P wave velocity (Vp) structure of the crust and upper mantle beneath Greenland and surrounding regions using the latest P wave arrival time data. The Greenland Ice Sheet Monitoring Network (GLISN), initiated in 2009, is an international project for seismic observation in these regions using 34 stations. We use a regional seismic tomography method to simultaneously invert P wave arrival times of local earthquakes and P wave relative traveltime residuals of teleseismic events. These data are extracted from the ISC-EHB catalog; however, for the teleseismic data, we picked new arrival times from seismograms using a cross-correlation method. Our tomographic results clearly reveal the Iceland plume, the Jan Mayen plume, and a newly discovered "Svalbard plume," which merge together in the mantle transition zone. A high-Vp body exists beneath the Greenland Sea, which might act as an obstacle against the rising Svalbard plume. Furthermore, our results reveal a remarkable low-Vp anomaly elongated in the NW-SE direction at depths ≤250 km beneath central Greenland, which is connected with the Iceland and Jan Mayen hotspots. Although previous studies have suggested a similar feature, our result is the first to show the low-Vp zone existing at all depths in the Greenland lithosphere, and its spatial distribution coincides with a high heat flux region. These characteristics indicate that the low-Vp zone reflects residual heat from the Iceland plume when the Greenland lithosphere passed over this plume at~80-20 Ma. Our results also indicate the possible existence of residual heat from the Jan Mayen plume. Plain Language Summary Greenland is a stable land mass that has preserved~4 Gyr of Earth's history. In its vicinity, there are the Mid-Atlantic Ridge, the Iceland and Jan Mayen hotspots, and a geothermal area in Svalbard, which indicate the complexity of this region. We apply seismic tomography to analyze the latest data recorded by a new seismograph network, and we obtain detailed 3-D images of the crust and upper mantle. Our results clearly image the conduit-like Iceland plume, the Jan Mayen plume, and a newly discovered "Svalbard plume," which merge together in the mantle transition zone. These new findings will improve our understanding of the tectonic and thermal evolution of this region. We also find a low seismic velocity zone running in the NW-SE direction beneath central Greenland, which is connected with the Iceland and Jan Mayen hotspots. This zone is located within the Greenlandic plate, and its spatial distribution agrees well with an area of high geothermal heat flux. These results suggest that the low-velocity zone reflects residual heat from the Iceland plume when the Greenlandic plate passed over the plume at~80-20 Ma. Our model further suggests a possible heat track left by the Jan Mayen plume.

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Section: Results Of Different Tomographic Inversionscontrasting

confidence: 56%

P Wave Tomography Beneath Greenland and Surrounding Regions: 1. Crust and Upper Mantle

2020

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“…Our results show a remarkable high‐ Vp anomaly at depths of 1,200–1,500 km beneath southwestern Greenland (Figure 5 and the F‐F′ section in Figure 6). This feature corresponds well to a possible slab remnant suggested by Shephard et al (2016) using the existing global tomography models (section 1). This study provides a more detailed view of this high‐ Vp anomaly by enhancing the tomographic resolution beneath Greenland.…”

Section: Discussionsupporting

confidence: 87%

“…The lower mantle structure beneath Greenland has not been studied well. Shephard et al (2016) reported a high‐ V zone at depths of 1,050–1,500 km beneath southwestern Greenland, which is found to be a common feature in many global tomography models (e.g., Ritsema et al, 2011; Simmons et al, 2010) and is interpreted as a subducted slab.…”

Section: Introductionmentioning

confidence: 99%

P Wave Tomography Beneath Greenland and Surrounding Regions: 2. Lower Mantle

2020

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We study the 3-D P wave velocity (Vp) structure of the whole mantle beneath Greenland and surrounding regions using the latest P wave arrival time data. We use a new method of global seismic tomography by setting 3-D grid nodes densely in the study volume to enhance the resolution. We invert~5.6 million arrival times of P, pP, and PP waves from 16,257 earthquakes extracted from the ISC-EHB catalog, which were recorded at 12,549 seismic stations in the world. Our results reveal a hot plume rising from the core-mantle boundary beneath central Greenland, which is called the Greenland plume. This plume has the main conduit and two branches in the lower mantle, and the main conduit rises to the mantle transition zone (MTZ) beneath eastern Greenland, so it is distinguishable from the Iceland plume that appears to rise from a midmantle depth (~1,500 km) beneath Iceland. The Iceland plume itself is a powerful plume, but it may also be fed by hot mantle materials from three joints with other plumes: a branch of the Greenland plume at~1,500 km depth, a plume beneath Western Europe at~1,000 km depth, and the main conduit of the Greenland plume at the MTZ, leading to many active volcanoes in Iceland. We deem that the main conduit of the Greenland plume mixes with the Iceland plume incompletely and splits mainly into the Jan Mayen and Svalbard plumes in the upper mantle, which supply magma to the Jan Mayen hotspot and a geothermal area in western Svalbard, respectively. Plain Language Summary Greenland and its surrounding regions have many clues for understanding global-scale tectonics of the Earth. Seismic tomography is a well-established method for obtaining 3-D images of the underground structure by inverting a large number of seismic wave arrival times. We obtain detailed tomographic images of the whole mantle beneath Greenland and adjacent regions using the latest dataset. Our high-resolution results show that the so-called Iceland plume could be composed of two plumes. One is located directly beneath Iceland but rising from~1,500 km depth, which we call the Iceland plume. The other is rising from the core-mantle boundary beneath central Greenland, which we call the Greenland plume. The Greenland plume has the main conduit and two branches in the lower mantle, and the main conduit rises to the mantle transition zone beneath eastern Greenland. Although the Iceland plume itself is a powerful plume, it may also have three joints with other plumes: the main conduit and a branch of the Greenland plume, and a plume beneath Western Europe, resulting in many active volcanoes in Iceland. The main conduit of the Greenland plume may also supply magmas to the Jan Mayen hotspot and a geothermal area in western Svalbard.

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“…The recent use of seismically identified slabs to validate, test or refine regional relative plate motions includes slabs located under North America 9 , the Pacific 10 , the Indian Ocean region 11 – 13 , Australia 14 , Siberia 15 , and Greenland 16 , amongst others. However, these studies often focus on a subset of one, two, or a small selection of available tomography models, and are often restricted to a single class of tomography data (e.g.…”

Section: Introductionmentioning

confidence: 99%

On the consistency of seismically imaged lower mantle slabs

Shephard

Matthews

Hosseini

et al. 2017

Sci Rep

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The geoscience community is increasingly utilizing seismic tomography to interpret mantle heterogeneity and its links to past tectonic and geodynamic processes. To assess the robustness and distribution of positive seismic anomalies, inferred as subducted slabs, we create a set of vote maps for the lower mantle with 14 global P-wave or S-wave tomography models. Based on a depth-dependent threshold metric, an average of 20% of any given tomography model depth is identified as a potential slab. However, upon combining the 14 models, the most consistent positive wavespeed features are identified by an increasing vote count. An overall peak in the most robust anomalies is found between 1000–1400 km depth, followed by a decline to a minimum around 2000 km. While this trend could reflect reduced tomographic resolution in the middle mantle, we show that it may alternatively relate to real changes in the time-dependent subduction flux and/or a mid-lower mantle viscosity increase. An apparent secondary peak in agreement below 2500 km depth may reflect the degree-two lower mantle slow seismic structures. Vote maps illustrate the potential shortcomings of using a limited number or type of tomography models and slab threshold criteria.

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Evidence for slab material under Greenland and links to Cretaceous High Arctic magmatism

Cited by 18 publications

References 56 publications

P Wave Tomography Beneath Greenland and Surrounding Regions: 1. Crust and Upper Mantle

P Wave Tomography Beneath Greenland and Surrounding Regions: 1. Crust and Upper Mantle

P Wave Tomography Beneath Greenland and Surrounding Regions: 2. Lower Mantle

On the consistency of seismically imaged lower mantle slabs

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