Magnetic Mineral Populations in Lower Oceanic Crustal Gabbros (Atlantis Bank, SW Indian Ridge): Implications for Marine Magnetic Anomalies

• Published in: Geochemistry, geophysics, geosystems : G3 geophysics, geosystems : G3, 2020-03, Vol.21 (3), p.n/a
• Main Authors: Bowles, J. A., Morris, A., Tivey, M. A., Lascu, I.
• Format: Article
• Language: English
• Subjects: Anomalies; Drilling; Expedition 360; Gabbros; Hydrothermal alteration; IODP; JOIDES Resolution; Magnetic anomalies; Magnetic field; Magnetic fields; magnetic mineralogy; Magnetic properties; Magnetism; Magnetite; marine magnetic anomalies; Microscopy; Minerals; ocean crust magnetization; Ocean floor; Oceanic crust; Oceans; Olivine; Oxide minerals; Oxides; Plagioclase; Pyroxenes; Remanent magnetization; Rocks; Sediment samples; Volcanic eruptions
• ISSN: 1525-2027; 1525-2027
• DOI: 10.1029/2019GC008847

To learn more about magnetic properties of the lower ocean crust and its contributions to marine magnetic anomalies, gabbro samples were collected from International Ocean Discovery Program Hole U1473A at Atlantis Bank on the Southwest Indian Ridge. Detailed magnetic property work links certain magnetic behaviors and domain states to specific magnetic mineral populations. Measurements on whole rocks and mineral separates included magnetic hysteresis, first‐order reversal curves, low‐temperature remanence measurements, thermomagnetic analysis, and magnetic force microscopy. Characteristics of the thermomagnetic data indicate that the upper ~500 m of the hole has undergone hydrothermal alteration. The thermomagnetic and natural remanent magnetization data are consistent with earlier observations from Hole 735B that show remanence arises from low‐Ti magnetite and that natural remanent magnetizations are up to 25 A m−1 in evolved Fe‐Ti oxide gabbros, but are mostly