Imaging downward granitic magma transport in the Rogaland Igneous Complex, SW Norway |
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Authors: | OlivierBolle,Ricardo I. F. Trindade,JeanLuc Bouchez,& Jean-ClairDuchesne |
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Affiliation: | Equipe de Pétrophysique, Tectonique et Géomorphologie, LMTG/OMP, UMR CNRS #5563, UniversitéPaul-Sabatier, 31400 Toulouse, France,;L.A. Géologie, Pétrologie et Géochimie, Universitéde Liège, 4000 Sart Tilman, Belgium |
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Abstract: | Combining geological mapping and petrological, structural and geophysical (gravity and seismic) data already available for the late Proterozoic Rogaland Igneous Complex of Norway allows the 3D shape of the Bjerkreim–Sokndal layered intrusion to be modelled as a thick cumulate series capped by massive granitic rocks. Using the latter data, along with the spectacular convergent linear flow pattern that covers both the cumulates and the felsic rocks of this chamber, evidence is presented to show that the granitic material was down-dragged through the sinking of its high-density mafic floor into lower density anorthosites and granulitic gneisses. This example illustrates that downward gravity-driven flows of rocks were active, in addition to upward flows, in the building of the early crust up to late-Proterozoic times, helping to explain the geochemical and structural complexities of the old crust. |
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