Magneto-mineralogy and magnetic properties of ocean floor basalts

Author(s): Petersen, Nikolai; Körner, Ulrike
Author Affiliation(s): Primary:
Ludwig-Maximilians Universität München, Institut für Geophysik, Munich, Germany
Volume Title: Magnetism; rocks to superconductors
Volume Author(s): Subbarao, K. V., editor
Source: Magnetism; rocks to superconductors, edited by K. V. Subbarao. Memoir - Geological Society of India, Vol.29, p.1-25. Publisher: Geological Society of India, Bangalore, India. ISSN: 0435-4001 CODEN: GSINAZ
Note: In English. 61 refs.; illus., incl. 1 table
Summary: The correlation between submarine weathering and magnetic properties of ocean floor basalts has been studied on basalt samples from the Atlantic and Pacific Oceans and the Mediterranean Sea. The natural magnetization of ocean floor basalts is carried by small grains of titanomagnetite with an average volume content of 1%. The primary titanomagnetite composition in oceanic basalts varies only within narrow limits. Under suboceanic conditions the primary titanomagnetites are gradually oxidized and form thereby cation deficient spinels. The process underlying this form of oxidation is Fe-migration out of the spinel lattice of the titanomagnetites. Submarine titanomagnetite oxidation causes the magnetic properties of ocean floor basalts to change in a characteristic way. Curie temperature increases with increasing titanomagnetite oxidation state z, i.e. with increasing age of the oceanic crust, whereas the intensity of magnetization decreases first, until z = 0.6 and increases thereafter at high z-values. The variation of the natural remanent magnetization of oceanic ballasts can qualitatively be explained by a simple model of Fe-migration: For titanomagnetite oxidation states up to z = 0.6 vacancies are preferentially formed on the octahedral sites of the spinel lattice. Beyond this z-value vacancies are formed only on the tetrahedral sites.
Year of Publication: 1994
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; Atlantic Ocean; Basalts; Chemical composition; Crust; Curie point; DSDP Site 395; DSDP Site 524; Deep Sea Drilling Project; IPOD; Igneous rocks; Iron; Lattice; Leg 73; Magnetic field; Magnetic properties; Magnetization; Mediterranean Sea; Metals; Migration of elements; Mineral composition; Natural remanent magnetization; ODP Site 648; Ocean Drilling Program; Ocean floors; Oceanic crust; Oxidation; Oxides; Pacific Ocean; Paleomagnetism; Remanent magnetization; Spinel structure; Temperature; Tholeiitic composition; Titanomagnetite; Volcanic rocks
Coordinates: N224521 N224521 W0460454 W0460454
S292904 S292902 W0023044 W0023045
N225518 N225520 W0445649 W0445650
Record ID: 2015110353
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.