Transport of mafic magma through the crust and sedimentary basins: Jameson Land, East Greenland

Abstract

Igneous sheet-complexes transport magma through the crust, but most studies have focused on single segments of the magma transport system or have low resolution. In the Jameson Land Basin in East Greenland, seismic reflection data and extensive outcrops give unparalleled constraints on mafic intrusions down to 15 km. This dataset shows how sill-complexes develop and how magma is transported from the mantle through sedimentary basins. The feeder zone of the sill-complex is a narrow zone below a basin, where a magmatic underplate body impinges on thinned crust. Magma is transported through the crystalline crust through dykes. Seismic data and published geochemistry indicate that magma is supplied from a magmatic underplate without perceptible storage in crustal magma chambers and crustal assimilation. As magma enters the sedimentary basin, it forms distributed, bowl-shaped sill-complexes throughout the basin. Large magma volumes in sills (4–20 times larger than the Skaergaard Intrusion) and the presence of few dykes highlight the importance of sills in crustal magma transport. On scales smaller than 0.2 km, host-rock lithology, and particularly mudstone tensile strength anisotropy, controls sill architecture in the upper 10 km of the basin, whereas sills are bowl-shaped below the brittle–ductile transition zone. On scales of kilometres and towards basin margins, tectonic stresses and lateral lithological changes dominate architecture of sills.Supplementary material: An uninterpreted and unwarped version of the seismic line in Fig. 4 (DR1), a spreadsheet showing thickness of sills and width of dykes in the study area (DR2), and assumptions and calculations of magma volume (DR3) are available at https://doi.org/10.6084/m9.figshare.c.5670470

Seismic Volcanostratigraphy: The Key to Resolving the Jan Mayen Microcontinent and Iceland Plateau Rift Evolution

“…Similar observations have been reported for the Jameson Land Basin and Scoresby Sund area by Eide et al. (2021) in East Greenland.…”

“…The Vøring margin is interpreted to contain a high-velocity lower crustal body that was generated by magmatic underplating, possibly associated with magma leaking along a large-scale fracture zone (e.g., Abdelmalak, et al, 2016;Gernigon et al, 2019Gernigon et al, , 2021. Similar observations have been reported for the Jameson Land Basin and Scoresby Sund area by Eide et al (2021) in East Greenland.…”

“…Fault trends and the SW‐NE‐striking magnetic anomaly interpreted across the Geikie plateau appear to terminate against the JMMC (Figures 11a and 14; Supplement 8 in Supporting Information ). This is interpreted as indirect evidence for intrusive complexes located within pre‐breakup sediments just north of Kap Brewster at the mouth of the Scoresby Sund and observed on seismic reflection data throughout the Jameson Land Basin (e.g., Blischke & Erlendsson, 2018; Eide et al., 2021) (Figure 11a). The Geikie plateau structures have distinct magnetic trends associated with pre‐breakup and breakup lava flows that cover the area.…”

“…The marked north‐to‐south increase in thickness of the pre‐breakup lower series and plateau basalt sections of the Blosseville Kyst, from ‘absent’ to up to 6–7 km suggests a deep‐seated source located at the intersection of the Blosseville Kyst and the proto‐Iceland‐Faroe Fracture Zone (Figure 11a). Furthermore, large deep‐seated igneous sources appear to be located close to the Scoresby Sund and Geikie plateau as distinct magnetic anomalies are present adjacent to the southern end of the Jameson Land Basin, and alongside extensive intrusive systems within the sedimentary basins of Jameson Land, Liverpool Land and the continental margin of the Blosseville Kyst (Figure 11a; Supplement 8 in Supporting Information ) (e.g., Blischke & Erlendsson, 2018; Eide et al., 2021; Franke et al., 2019; Guarnieri et al., 2016).…”

Magnetic fabrics reveal three-dimensional flow processes within elongate magma fingers at the margin of the Shonkin Sag laccolith (MT, USA)

“…Magma transport in the Earth's upper crust is facilitated by networks of interconnected sheet intrusions (i.e., sills and dykes) (e.g., Anderson, 1937Anderson, , 1951Elliot and Fleming, 2004;Leat, 2008;Muirhead et al, 2012;Magee et al, 2016a;Schofield et al, 2017;Eide et al, 2021). These sills and dykes commonly form via the coalescence of discrete, laterally restricted elements, such as magma fingers and segments (Fig.…”