North Atlantic hotspot-ridge interaction near Jan Mayen Island

Abstract

At slow to ultraslow spreading rates along mid-ocean ridges, thicker lithosphere typically impedes magma generation and tectonic extension can play a more significant role in crustal production (Dick et al., 2003). The source of anomalously high magma supply thus remains unclear along ridges with ultraslow-spreading rates adjacent to Jan Mayen Island in the North Atlantic (Neumann and Schilling, 1984;Mertz et al., 1991; Haase et al., 1996;Schilling et al., 1999;Trønnes et al., 1999; Haase et al., 2003;Mertz et al., 2004;Blichert-Toft et al., 2005; Debaille et al., 2009). Here we show that Jan Mayen volcanism is likely the surface expression of a small mantle plume, which exerts significant influence on nearby mid-ocean ridge tectonics and volcanism. Progressive dilution of Jan Mayen geochemical signatures with distance from the hotspot is observed in lava samples from the immediately adjacent Mohns Ridge, and morphological indicators of enhanced magma supply are observed on both the Mohns Ridge and the nearby Kolbeinsey Ridge, which additionally locally overlies a highly heterogeneous, eclogite-bearing mantle source. These morphological and geochemical influences underscore the importance of heterogeneous mantle sources in modifying melt supply and thus the local expression of tectonic boundaries. LetterThe normal accretion process along divergent plate boundaries can be notably altered in hotspot-ridge interaction settings, where elevated mantle temperature anomalies enhance mantle melting, generating unusually thick oceanic crust (e.g., Schilling et al., 1985;Schilling, 1991; Gale et al., 2013 Gale et al., , 2014. Jan Mayen and its immediate environs in the North Atlantic (Fig. 1) include an intraplate, volcanically-active island or hotspot (Jan Mayen Island), positioned at the northern terminus of a small, rifted microcontinent (Jan Mayen Ridge; Johnson and Heezen, 1967; Kodaira et al., 1997; Gaina et al., 2009) and adjacent to two second-order ultraslow-spreading (Dick et al., 2003) ridge segments, the Northern Kolbeinsey Ridge (NKR) and Southern Mohns Ridge (SMR), and the Jan Mayen Fracture Zone, a major fracture zone with ~200 km of transform offset. Although different in key ways, broad geochemical similarities between Jan Mayen Island and Icelandic lavas have suggested the influence of a mantle plume (either a unique Jan Mayen plume or emplaced Icelandic material) on mantle melting beneath Jan Mayen Island (Schilling et al., 1999;Trønnes et al., 1999; Debaille et al., 2009). The absence of a clear hotspot track has led to conflicting, alternate interpretations for Jan Mayen's high magma production rate and enriched chemistry (Imsland, 1986;Maaløe et al., 1986;Thy et al., 1991): cold edge effects near the fracture zone (Mertz et al., 1991; Haase et al., 1996), variably melting source heterogeneities (Mertz et al., 1991; Haase et al., 2003;Mertz et al., 2004), upwelling along a mantle chemical discontinuity (Blichert-Toft et al., 2005), or a locally wet mantle (Haase et al., 2003;Mertz et al., 2004)....

Lithospheric Control on Asthenospheric Flow From the Iceland Plume: 3‐D Density Modeling of the Jan Mayen‐East Greenland Region, NE Atlantic

“…A sensitivity test shows that if the Moho depth of western NKR domain is decreased by 3 km, then this would make the uppermost mantle density more symmetrical over the NKR. However, with a symmetrical low-density distribution, the present magmatism along the NKR would show melting under elevated mantle temperature, but this is inconsistent with geochemical studies (e.g., Elkins et al, 2016;Haase et al, 2003). Also, the eastern displacement of the negative uppermost mantle density anomaly under the NKR is continuous with that of the better constrained MKR domain to the south, as well as to that of the southern Mohn's Ridge to the north, suggesting that our preferred model is reasonable.…”

“…This redirection of the plume flow could also help to explain why the present spreading at the NKR does not appear to be influenced by elevated mantle temperature. Rather, it is known to be sourced from an enriched mantle component different from the MKR (e.g., Elkins et al, , ; Haase et al, ). Thus, neither geochemical data nor our results can confirm a model where ponding of northward plume flow occurs against a lithospheric thickness increase at the northern end of the Kolbeinsey Ridge.…”

“…Previous studies, including (i) the interpretation of reflection seismic data (Blischke et al, 2016;Peron-Pinvidic et al, 2012a, 2012b, (ii) wide-angle refraction seismic data (Breivik, Mjelde, Faleide, Murai, 2012;Hermann & Jokat, 2016;Kandilarov et al, 2012Kandilarov et al, , 2015Klingelhöfer, Géli, & White, 2000;Klingelhöfer, Géli, Matias, et. al., 2000;Kodaira et al, 1997Kodaira et al, , 1998bTan et al, 2017;Voss & Jokat, 2007;Weigel et al, 1995), and (iii) studies of dredged samples (e.g., Elkins et al, 2011Elkins et al, , 2016Haase et al, 2003;Klingelhöfer, Géli, & White, 2000;Mertz et al, 2004;Schilling, 1999), show that the study area is characterized by large variations in terms of crustal structure as well as mantle composition, and mantle melting degree. Table 1 and Figure 1 provide an overview of the data types and sources used to develop a 3-D structural and density model for the crystalline crust and sedimentary cover.…”

“…Such steps in the lithosphere-asthenosphere boundary have been postulated to control the emplacement of plume material (plume ponding; Sleep, 1997) and could potentially accumulate plume material from a northward flow out from the Iceland plume under the Eggvin Bank, if the flow was strongly directed by the spreading ridge. Elkins et al (2016) and Schilling (1999) argue that excess magmatism in the NKR domain is caused by a putative Jan Mayen plume. However, Mertz et al (2004) argue that the plume does not follow a simple time-transgressive track and cannot explain the radiogenic Nd-Pb isotope compositions of basalts from the NKR.…”

Crustal structure and origin of the Eggvin Bank west of Jan Mayen, NE Atlantic

“…None of the seamounts along Profile‐1 have been sampled, although several studies have sampled younger seamounts nearby as well as the seafloor spreading axis (Figure ). The dredged samples from NKR, near‐axis, and off‐axis seamounts at the Eggvin Bank are enriched in incompatible elements [ Campsie et al , ; Haase et al , ; Mertz et al , ; Elkins et al , , ]. This indicates elevated proportions of enriched source components under the NKR and surrounding Eggvin Bank at the present and probably also in the past.…”