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

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doi: 10.1016/j.pepi.2005.08.005
Author(s): Zhao, Xixi; Riisager, Peter; Antretter, Marie; Carlut, Julie; Lippert, Peter; Liu, Qingsong; Galbrun, Bruno; Hall, Stuart; Delius, Heike; Kanamatsu, Toshiya
Author Affiliation(s): Primary:
University of California at Santa Cruz, Center for Study of Imaging and Dynamics of the Earth, Santa Cruz, CA, United States
Other:
University of California at Davis, United States
Florida International University, United States
University of Hawaii at Manoa, United States
University of Lund, Sweden
University of München, Federal Republic of Germany
Ecole Normale Superieure, France
Université Paris VI, France
University of Houston, United States
University of Leicester, United Kingdom
JAMSTEC, Japan
Volume Title: ODP contributions to paleomagnetism
Volume Author(s): Sager, William W., editor; Acton, Gary D.; Clement, Bradford M.; Fuller, Michael
Source: ODP contributions to paleomagnetism, edited by William W. Sager, Gary D. Acton, Bradford M. Clement and Michael Fuller. Physics of the Earth and Planetary Interiors, 156(3-4), p.294-328. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0031-9201 CODEN: PEPIAM
Note: In English. 68 refs.; illus., incl. 1 table, sketch map
Summary: Previous rock magnetic investigations of oceanic basement samples have been mainly restricted by single drill holes or 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°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°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. For the serpentinized peridotites recovered from both sides of the Newfoundland-Iberia rifted margins, results from low-temperature measurements show that (titano)magnetites are present in the dark-colored peridotites, with a strong Verwey transition in the vicinity of 110 K, and with field- and frequency-dependent susceptibility curves that resemble those of synthetic TM0. In contrast to the magnetic properties observed from the dark-colored peridotites, the low-temperature curves for the yellow-brown-colored peridotites did not show any Verwey transition. Thermomagnetic analysis also failed to show evidence for titanomagnetites. The remanent magnetization is carried by a thermally unstable mineral that breaks down at about 420°C, probably maghemite. The magnetic signatures of the serpentinized peridotites recovered from both sides of the Newfoundland-Iberia rift appear not in conflict with the notion that conjugate margins will have generally similar crustal structure and evolution history. Our rock magnetic data indicate that the differences in the rock magnetic properties of basaltic rocks are mainly a function of mineralogy and alteration. There is no apparent coincidence between the age of the rocks and the degree of low-temperature alteration, as suggested by the presence of nearly unoxidized titanomagnetite in the Cretaceous aged basalts and by an examination of Curie temperature versus sample age that does not unambiguously show a positive relationship between the degree of low-temperature oxidation and crust ages. Abstract Copyright (2006) Elsevier, B.V.
Year of Publication: 2006
Research Program: ODP Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; Alteration; Atlantic Ocean; Basalts; Broken Ridge; Canada; Cenozoic; Characterization; Continental margin; Crust; Curie point; Eastern Canada; Europe; Iberian Peninsula; Igneous rocks; Indian Ocean; Intrusions; Kerguelen Plateau; Leg 158; Leg 173; Leg 183; Leg 192; Leg 203; Low temperature; Magnetic hysteresis; Magnetic minerals; Magnetic properties; Magnetic susceptibility; Magnetization; Metasomatism; Mid-Atlantic Ridge; Mid-ocean ridge basalts; Mossbauer spectra; Newfoundland; Newfoundland Island; Newfoundland and Labrador; North Atlantic; Ocean Drilling Program; Oceanic crust; Ontong Java Plateau; Ophiolite; Pacific Ocean; Paleomagnetism; Peridotites; Plate tectonics; Pleistocene; Plutonic rocks; Quaternary; Rifting; Serpentinization; Sills; Southern Europe; Spectra; TAG hydrothermal field; Temperature; Ultramafics; Volcanic rocks; West Pacific
Coordinates: N404000 N404800 W0110000 W0130000
N260812 N260814 W0444933 W0444935
N051800 N051800 W1100400 W1100500
S050100 N010000 E1643000 E1570000
S600000 S320000 E0980000 E0630000
Record ID: 2007053215
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands