Dyke architecture, mineral layering, and magmatic convection; new perspectives from the Younger Giant Dyke Complex, S Greenland

• Published in: Geochemistry, Geophysics, Geosystems
• Main Authors: Koopmans, L., McCarthy, W., Magee, C.
• Other Authors: University of St Andrews. School of Earth & Environmental Sciences, University of St Andrews. St Andrews Isotope Geochemistry
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2022
• Subjects: Anisotropy of magnetic susceptibility; Layered igneous systems; Rock magnetics; Magma chamber processes; Mesoproterozoic; Sheet segmentation; QE Geology; DAS; MCC; QE; Courtauld; Greenland; Scott Polar Research Institute
• Online Access: http://hdl.handle.net/10023/24978; https://doi.org/10.1029/2021GC010260

The expedition was funded by the Mining Institute of Scotland Trust, the Institute of Materials, Minerals and Mining, the Society of Economic Geologists Hickok-Radford Fund, the Edinburgh Geological Society, the Augustine Courtauld trust and the Scott Polar Research Institute. Igneous sheet intrusions are a fundamental component of volcano plumbing systems. Identifying how sheet intrusion emplacement and geometry controls later magmatic processes is critical to understanding the distribution of volcanic eruptions and magma-related ore deposits. Using the Younger Giant Dyke Complex, a Mesoproterozoic suite of large (< 800 m wide) mafic dykes in southern Greenland, we assess the influence sheet of emplacement and geometry on subsequent magma flow and mush evolution. Through structural mapping, petrographic observations, and anisotropy of magnetic susceptibility fabric analyses, we show that the Younger Giant Dyke Complex was emplaced as a series of individual dyke segments, which following coalescence into a sheet intrusion remained largely isolated during their magmatic evolution. Through petrographic evidence for liquid-rich growth of cumulus phases, concentric magnetic fabrics, and the detailed study layered zones within the Younger Giant Dyke Complex, we infer magma convection occurred within the cores of each dyke element. We particularly relate layering to hydrodynamic sorting processes at a magma-mush boundary towards the base of each convection cell. Overall, our work demonstrates that the initial geometry of sheet intrusions can constrain magma flow patterns and affect the distribution of crystallisation regimes. Publisher PDF Peer reviewed