Open AccessDyke Architecture, Mineral Layering, and Magmatic Convection; New Perspectives From the Younger Giant Dyke Complex, S Greenland
Author(s) -
Koopmans L.,
McCarthy W.,
Magee C.
Publication year - 2022
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2021gc010260
Subject(s) - geology , magma chamber , igneous rock , petrography , layering , layered intrusion , magma , petrology , igneous differentiation , geochemistry , dike , volcano , sill , large igneous province , geophysics , mafic , magmatism , seismology , tectonics , botany , biology
Abstract 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 (YGDC), 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 YGDC 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 YGDC, 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 toward 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 crystallization regimes.