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.
| Original language | English |
|---|---|
| Article number | jgs2021-043 |
| Number of pages | 20 |
| Journal | Journal of the Geological Society |
| Volume | 179 |
| Issue number | 3 |
| Early online date | 28 Oct 2021 |
| DOIs | |
| Publication status | Published - 1 May 2022 |
Bibliographical note
Acknowledgements:We thank reviewers Sam Poppe, Janine Kavanagh and Christian Tegner for thorough reviews that significantly improved this paper. Funding for data acquisition was provided from the Research Council of Norway through the PETROMAKS project 193059 and the FORCE Safari project.
Funding for data analysis provided from PETROMAKS through the ISBAR project 267689. Dougal Jerram is partly funded through the Research Council of Norway through its Centre of Excellence funding scheme, project number 223272, CEED. We acknowledge Geological Survey of Denmark and Greenland (GEUS) for access to, and permission to publish images of, onshore seismic data acquired by Atlantic Richfield Company (ARCO). Schlumberger are acknowledged for an academic license for Petrel which was used for seismic interpretation and visualization. Gijs Henstra, Bjørn Nyberg and Simon Buckley are thanked for assistance with fieldwork and data processing. The virtual outcrop was visualized and interpreted using LIME (http://virtualoutcrop.com/lime; Buckley et al 2019). The outcrop dataset at Hurry Inlet is available from the VOG group at
https://v3geo.com/model/61.
Data Availability Statement
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.5670470Proprietory seismic data are available from GEUS for a fee. The outcrop dataset for Hurry Inlet is available from the VOG group at https://v3geo.com/model/61. Scientific editing by Renjie Zhou