Unraveling the magnetic carriers of igneous cores from the Atlantic, Pacific, and the southern Indian oceans with rock magnetic characterization

• Published in: Physics of the Earth and Planetary Interiors
• Main Authors: Zhao, XX, Riisager, Peter, Antretter, M, Carlut, J, Lippert, P, Liu, QS, Galbrun, B, Hall, S, Delius, H, Kanamatsu, T
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2006
• Subjects: Geology; serpentinized peridotite; basalt; low-temperature properties; curie temperature; hysteresis loop; Ocean Drilling Program; Kerguelen; Pacific; Indian; Broken Ridge; Newfoundland
• Online Access: https://lup.lub.lu.se/record/404350; https://doi.org/10.1016/j.pepi.2005.08.005

Previous rock magnetic investigations of oceanic basement samples have been mainly restricted by single drill holes of dredge collections. In this study, we present new and published data on the rock magnetic properties of igneous rock samples recovered during seven Ocean Drilling Program (ODP) legs in the Atlantic, Pacific, and the southern Indian oceans. The recovered igneous rocks from these legs are mainly basaltic flows (both submarine and subaerial), diabase sills, and serpentinized peridotites, with approximate ages of 140,000 years, 10-12, 34, 69, 100-108, and 110-121 Ma, which offers an opportunity to investigate magnetic properties and mineral changes attending alteration of basement rocks over a wide range of ages from variable tectonic settings. Titanomagnetite and titanomaghemite are commonly present in igneous rock samples of the Ontong Java Plateau, the Kerguelen Plateau/Broken Ridge, the eastern Equatorial Pacific, the middle Atlantic ridge (Trans-Atlantic Geotraverse area), and the Newfoundland-Iberia rifted margins. For basaltic rock samples, three general groups (A, B, and C, respectively) can be divided in terms of rock magnetic properties. Samples from group A have a single phase of Ti-poor titanomagnetite with Curie temperatures ranging between 480 and 580 degrees C and exhibit a strong Verwey transition in the vicinity of 110 K. Basalts from this group are most likely good paleomagnetic recorders and probably have preserved original and stable magnetic remanences. Group B is mainly observed in pillow lavas and is characterized by a Curie temperature of 260-280 degrees C, which is typical of low-temperature oxidized titanomaghemite or titanium rich titanomagnetite. The low-temperature curves for group B do not show the Verwey transition. Group C has more than one Curie temperature, which suggests the presence of multiple magnetic phases. The thermomagnetic signature indicates the inversion of titanomaghemite to a strongly magnetized magnetite, as shown by the irreversible cooling curves. ...