A new oil-window indicator? The magnetic assemblage of claystones from the Baffin Bay volcanic margin (Greenland)

• Published in: AAPG Bulletin
• Main Authors: Mansour Abdelmalak, Mohamed, Aubourg, Charles, Geoffroy, Laurent, Laggoun-Défarge, Fatima
• Other Authors: Laboratoire de Planétologie et Géodynamique UMR 6112 (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), 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), Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Bureau de Recherches Géologiques et Minières (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2012
• Subjects: [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; [SDE.MCG]Environmental Sciences/Global Changes; Baffin Bay; Baffin; Greenland
• Online Access: https://insu.hal.science/insu-00687471; https://doi.org/10.1306/07121111008

International audience Identifying independent parameters to bracket the oil window in sedimentary basins is of first importance for petroleum exploration. We investigate the magnetic assemblage of Cretaceous claystones collected from the western volcanic margin of Greenland. These claystones experienced low-grade burial (<5 km). To assess the maturity of organic matter, we measured the vitrinite reflectance (Ro) and the temperature at maximum release of hydrocarbons (Tmax) that occurs during Rock-Eval pyrolysis. These data (0.37% ≤ Ro ≤ 2%, 422°C ≤ Tmax ≤ 604°C) show that most claystones are immature to mature with respect to the oil window. We suggest that magnetic minerals can be an indication of burial temperature. The magnetic assemblage of the same samples is elucidated by lowtemperature (<300 K) and high-temperature (>300 K) properties of isothermal remanent magnetization. The magnetic assemblage of immature claystones (lower Ro) resides in goethite, greigite, and some magnetite. The magnetic assemblage of immature to early mature claystones (higher Ro) resides in stoichiometric magnetite and fine-grained pyrrhotite. By comparing these results with those from claystones from the Paris Basin (France) and the Jura Mountains (Switzerland), we suggest the existence of similar mechanisms for the formation of magnetic minerals during burial. If confirmed by further studies, the magnetic assemblage of claystones may be diagnostic of oil windows.