Detecting the thermal aureole of a magmatic intrusion in immature to mature sediments: a case study in the East Greenland Basin (73◦N)

• Published in: Geophysical Journal International
• Main Authors: Aubourg, Charles, Techer, Isabelle, Geoffroy, Laurent, Clauer, Norbert, Baudin, François
• Other Authors: Laboratoire des Fluides Complexes et leurs Réservoirs (LFCR), TOTAL FINA ELF-Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Hydrologie et de Géochimie de Strasbourg (LHyGeS), Ecole et Observatoire des Sciences de la Terre (EOST), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Nationale du Génie de l'Eau et de l'Environnement de Strasbourg (ENGEES)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre de Paris (iSTeP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: Continental margins: divergent; Magnetic mineralogy and petrology; Pluton emplacement; Arctic region; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics; Arctic; Greenland; Greenland Basin; East Greenland
• Online Access: https://hal.science/hal-00903412; https://hal.science/hal-00903412/document; https://hal.science/hal-00903412/file/2013_Aubourg_Groenland%20GJI_ADep.pdf; https://doi.org/10.1093/gji/ggt396

International audience The Cretaceous and Triassic argillaceous rocks from the passive margin of Greenland have been investigated in order to detect the thermal aureole of magmatic intrusions, ranging from metric dyke to kilometric syenite pluton. Rock-Eval data (Tmax generally <468 ◦C), vitrinite reflectance data (R₀ < 0.9 per cent) and illite cristallinity data (ICI > 0.3), all indicate a maximum of 5km burial for the argillaceous rocks whatever the distance to an intrusion. The K-Ar dating of the clays <2 μm fraction suggests that illites are mostly detrital, except near magmatic intrusions where younger ages are recorded. To get more information about the extent of the thermal aureole, rock magnetism data were determined. At distance away from the thermal aureole of the syenite intrusion, Triassic argillaceous rocks reveal a standard magnetic assemblage compatible with their burial (R₀ ∼ 0.4 percent). It is constituted essentially by neoformed stoichiometric magnetite (Fe₃O₄. In contrast, within the thermal aureole of the magmatic intrusions, the Cretaceous argillaceous rocks contain micron-sized pyrrhotite (Fe₇S₈, firmly identified through the recognition of Besnus transition at 35K. The thermal demagnetization of natural remanence carried by this pyrrhotite shows a diagnostic 'square shouldered' pattern, indicating a narrow grain size distribution of pyrrhotite. The extension of this diagnostic pyrrhotite maps a ∼10-km-thick aureole around the syenitic pluton. Away from this aureole, the magnetic assemblage is diagnostic of those found in argillaceous rocks where organic matter is mature.