Continental crust beneath southeast Iceland

Abstract

The magmatic activity (0–16 Ma) in Iceland is linked to a deep mantle plume that has been active for the past 62 My. Icelandic and northeast Atlantic basalts contain variable proportions of two enriched components, interpreted as recycled oceanic crust supplied by the plume, and subcontinental lithospheric mantle derived from the nearby continental margins. A restricted area in southeast Iceland—and especially the Öræfajökull volcano—is characterized by a unique enriched-mantle component (EM2-like) with elevated 87Sr/86Sr and 207Pb/204Pb. Here, we demonstrate through modeling of Sr–Nd–Pb abundances and isotope ratios that the primitive Öræfajökull melts could have assimilated 2–6% of underlying continental crust before differentiating to more evolved melts. From inversion of gravity anomaly data (crustal thickness), analysis of regional magnetic data, and plate reconstructions, we propose that continental crust beneath southeast Iceland is part of ∼350-km-long and 70-km-wide extension of the Jan Mayen Microcontinent (JMM). The extended JMM was marginal to East Greenland but detached in the Early Eocene (between 52 and 47 Mya); by the Oligocene (27 Mya), all parts of the JMM permanently became part of the Eurasian plate following a westward ridge jump in the direction of the Iceland plume.

Break-up and seafloor spreading domains in the NE Atlantic

“…The position of interpreted COBs is not sufficient to infer the presence of an additional continental tectonic block, as COB interpretations could be subjective. However, the gap in the reconstruction, plus evidence of buried continental crust under present-day SE Iceland, led Torsvik et al (2015) to suggest that the JMMC is much larger and its southern fragment, which is possibly buried under presentday SE Iceland, was rifted from the Greenland continental margin situated south of the Blosseville Coast (Fig. 5).…”

Geochemical stratigraphy and correlation within large igneous provinces: The final preserved stages of the Faroe Islands Basalt Group

“…Alternatively, a situation could be envisaged whereby the High-Ti melts were being produced within a more continuous melting region, with the LowTi lavas initially being fed into the High-Ti flow fields from an area of progressively thinning lithosphere to the west (e.g. The proposed site of the proto-Icelandic anomaly under either central (Lawver & Müller, 1994), or central east (Torsvik et al, 2015) Greenland at the time, could also potentially raise questions as to the presence of symmetrical melt columns on either side of the rift system. Upwelling mantle material convecting along the base of the lithosphere from the anomaly source (e.g.…”

A review of the NE Atlantic conjugate margins based on seismic refraction data

“…Foulger & Anderson (2005) proposed the presence of a microplate that may contain oceanic crust submerged beneath younger lavas. Recently, Torsvik et al (2015) suggested the presence of a sliver of continental crust beneath SE Iceland that links with the JMMC. This interpretation is based on geochemistry data.…”