Magnetic state of 10–40 Ma old ocean basalts and its implications for natural remanent magnetization

Matzka, Jürgen; Krása, David; Kunzmann, Thomas; Schult, A.; Petersen, N.

doi:10.1016/s0012-821x(02)01094-4

Cited by 48 publications

(58 citation statements)

References 35 publications

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“…Petersen et al 1979, Zhou et al 2001, Matzka et al 2003. This increase in z is well established by microprobe determinations of titanomagnetite compositions and lattice parameters.…”

Section: Discussionsupporting

confidence: 56%

“…The age dependence of magnetic properties of MORBs, i.e. their lateral variation with regard to oceanic spreading centres, has received particular attention (Bleil and Petersen 1983, Xu et al 1997, Tivey and Tucholke 1998, Zhou et al 1999b, Zhou et al 2001, Matzka et al 2003. The variation of magnetic properties with depth below seafloor has been described with much less detail, also because of the technical difficulties to obtain an undisturbed and complete section of oceanic basement.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic Mineralogy of a Complete Oceanic Crustal Section (IODP Hole 1256D)

Krása

Herrero‐Bervera²,

Rodriguez

2011

The Earth's Magnetic Interior

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Oceanic crust is the carrier of the marine magnetic anomalies and is therefore a valuable archive of geomagnetic information. ODP/IODP Hole 1256D was the first to sample an entire sequence of oceanic crust down to the gabbro. We studied the vertical variation of magnetic remanence carriers by means of scanning electron microscopy, microanalysis and rock magnetic measurements. The extrusive layer contains dendritic, low-temperature oxidized titanomagnetites (TMs), i.e. titanomaghemite, with initial compositions close to values previously reported for mid-ocean ridge basalts (MORB). The degree of low-temperature oxidation (maghemitisation) remains fairly constant across the extrusives. We explain the observed increase in Curie temperature with depth by submicron inversion of titanomaghemite to intergrowths of titanomagnetite and nonmagnetic phases, where the Ti-content of titanomagnetite is decreasing with depth. In the underlying sheeted dikes, TMs are again the primary magnetic mineral. Due to slower cooling, they are in most cases oxy-exsolved into lamellar intergrowths of Ti-poor TMs and ilmenite. The magnetominerals are altered to a much higher degree than in the extrusives. In the gabbroic part of the section, TMs reach sizes up to several mm, although the magnetic grain size remains consistently in the pseudo-single-domain range because of grain subdivision by exsolution lamellae. The extrusives carry a thermoremanent magnetisation (TRM), retaining the primary paleomagnetic direction but with a reduced remanence intensity. The sheeted dikes hold a thermo-chemical remanent magnetization (TCRM) or secondary TRM acquired during hydrothermal alteration, whereas the underlying gabbro acquired a TCRM significantly after emplacement due to slow cooling at this depth.

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“…Petersen et al 1979, Zhou et al 2001, Matzka et al 2003. This increase in z is well established by microprobe determinations of titanomagnetite compositions and lattice parameters.…”

Section: Discussionsupporting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Magnetic Mineralogy of a Complete Oceanic Crustal Section (IODP Hole 1256D)

Krása

Herrero‐Bervera²,

Rodriguez

2011

The Earth's Magnetic Interior

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“…If this is true, the stronger "maghemitized" (altered) sample (ST101.0) 721 shows much higher NRM intensity and χ, which opposes studies of e.g. Matzka et al (2003). 722…”

Section: High Temperature Deuteric Oxidation 608mentioning

confidence: 84%

The Stardalur magnetic anomaly revisited—New insights into a complex cooling and alteration history

Vahle

Kontny

Gunnlaugsson

et al. 2007

Physics of the Earth and Planetary Interiors

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“…In these two cases, the magnetizations in rocks are lowered, leading to underestimation of paleointensity. Low-temperature oxidation of titanomagnetites in ocean basalts is ubiquitous [e.g., Matzka et al, 2003;Bleil and Petersen, 1983;Johnson et al, 1996]. Even though primary TRMs in rocks are fortunately preserved in rocks [e.g., Zhou et al, 1999], one cannot determine the paleointensity from temperature intervals over 300°C when using the Thellier-Coe method, because magnetomineralogical inversion start.…”

Section: Discussionmentioning

confidence: 99%

Thermally induced inversion of Al‐substituted titanomagnetite in basalts: Evidence for partial self‐reversal

et al. 2006

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[1] We report properties of laboratory-induced thermoremanence combined with detailed rock magnetic experiments on basaltic samples which contain aluminum-substituted titanomagnetite (Fe 2.24 Ti 0.64 Al 0.12 O 4 ). Prior to Thellier-Coe paleointensity experiments, specimens were first demagnetized using an alternating field with a peak field of 90 mT and were then imparted an anhysteretic remanent magnetization (ARM) to represent a natural remanent magnetization (NRM). Results show that the partial thermal remanent magnetization (pTRM) gain and ARM remaining are linearly correlated up to 300°C. Between 300 and 460°C, specimens acquire thermoremanence with a direction antiparallel to the external field direction, leading to intensity decreases. This coincides with the onset of the mineral transformation from Al-titanomagnetite to a magnetic phase with higher T c . Our results support that phase interaction with distinct T c values in partially oxidized titanomagnetite can produce partial self-reversal thermoremanence in rocks.Citation: Pan, Y., Q. Liu, C. Deng, H. Qin, and R. Zhu (2006), Thermally induced inversion of Al-substituted titanomagnetite in basalts: Evidence for partial self-reversal,

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Magnetic state of 10–40 Ma old ocean basalts and its implications for natural remanent magnetization

Cited by 48 publications

References 35 publications

Magnetic Mineralogy of a Complete Oceanic Crustal Section (IODP Hole 1256D)

Magnetic Mineralogy of a Complete Oceanic Crustal Section (IODP Hole 1256D)

The Stardalur magnetic anomaly revisited—New insights into a complex cooling and alteration history

Thermally induced inversion of Al‐substituted titanomagnetite in basalts: Evidence for partial self‐reversal

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