Volcanic Structures and Magmatic Evolution of the Vesteris Seamount, Greenland Basin

Katharina A Unger Moreno,Janis Thal,Wolfgang Bach,Christoph Beier,Karsten M Haase

doi:10.3389/feart.2021.711910

Abstract

The formation of isolated seamounts distant from active plate boundaries and mantle plumes remains unsolved. The solitary intraplate volcano Vesteris Seamount is located in the Central Greenland Basin and rises ∼3,000 m above the seafloor with a total eruptive volume of ∼800 km3. Here, we present a new high-resolution bathymetry of Vesteris Seamount and a detailed raster terrain analysis, distinguishing cones, irregular volcanic ridges, volcanic debris fans, U-shaped channels and lava flows. The slope angles, ruggedness index and slope direction were combined with backscatter images to aid geologic interpretation. The new data show that the entire structure is a northeast to southwest elongated stellar-shaped seamount with an elongated, narrow summit surrounded by irregular volcanic ridges, separated by volcanic debris fans. Whole-rock geochemical data of 78 lava samples form tight liquid lines of descent with MgO concentrations ranging from 12.6 to 0.1 wt%, implying that all lavas evolved from a similar parental magma composition. Video footage from Remotely Operated Vehicle (ROV) dives shows abundant pyroclastic and hyaloclastite deposits on the summit and on the upper flanks, whereas lavas are restricted to flank cones. The seamount likely formed above a weak zone of the lithosphere possibly related to initial rifting parallel to the nearby Mohns Ridge, but the local stress field increasingly affected the structure of the volcano as it grew larger. Thus, we conclude that the evolution of Vesteris Seamount reflects the transition from deep, regional lithospheric stresses in the older structures to shallower, local stresses within the younger volcanic structures similar to other oceanic intraplate volcanoes. Our study shows how the combination of bathymetric, visual and geochemical data can be used to decipher the geological evolution of oceanic intraplate volcanoes.

Highlights

Volcanic seamounts are abundant bathymetric features on the seafloor and are typically related to island arcs, mid-ocean ridges, and hotspot chains and occur as solitary intraplate volcanoes (Wessel, 1997)
We suggest that Vesteris Seamount is a prime example of a large seamount growing above a lithospheric weak zone, which could be interpreted as an early indicator for a westward ridge jump of the Mohns Ridge
The initial formation of Vesteris Seamount was the result of deep, regional lithospheric stresses, whereas the current morphology of Vesteris is dominated by the local stress field within the volcanic edifice

Summary

Introduction

Volcanic seamounts are abundant bathymetric features on the seafloor and are typically related to island arcs, mid-ocean ridges, and hotspot chains and occur as solitary intraplate volcanoes (Wessel, 1997). Hotspot-related intraplate volcanoes frequently occur on relatively old and thick oceanic lithosphere and the magmas represent relatively low degrees of partial melting at Vesteris Seamount high pressures resulting in alkaline, enriched compositions (Haase, 1996; Humphreys and Niu, 2009). Well-studied examples are hotspot-related seamount chains like the Hawaiian-Emperor (Regelous et al, 2003; Buchs et al, 2015) and the Louisville Seamount Chains (Lonsdale, 1988; Koppers et al, 2004). These volcanic chains are explained by plate movement across a melting anomaly formed by a thermal deep mantle plume (Morgan, 1971; Duncan and Richards, 1991). Volatile-rich magmas may erupt explosively even at great water depth (Head and Wilson, 2003), and volcaniclastic rocks can be common contributors to the foundation of intraplate volcanoes (Clague et al, 1990; Helo et al, 2011)

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Conclusion