Toward a better theory of thermal remanent magnetization

Merrill, Ronald T.

doi:10.1029/jb086ib02p00937

Cited by 38 publications

(12 citation statements)

References 58 publications

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“…They showed that due to such stress centres PSD bulk moments could exist. Furthermore, Merrill (1981) showed that the maximum degree of screening is 75 per cent, which is less than previously assumed.…”

Section: Psd Effectsmentioning

confidence: 68%

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TRM, ARM and Isr of two natural magnetites of MD and PSD grain size

Hartstra¹

1983

Geophysical Journal International

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Summary. TRM, ARM and Isr stabilities with respect to alternating fields and high‐ and low‐temperature treatment are compared for a set of artificial rock specimens. The specimens contain grain‐size fractions of a homogeneous natural magnetite and a natural magnetite showing exsolution lamellae. The grain‐size fractions are in the PSD‐MD range and vary between < 5 and 250 μm. For large MD grains the coercivity spectra of ARM are similar to those of Isr but differ from those of TRM particularly in the lower part of the spectrum. For small (< 5μm) grains the coercivity spectrum of ARM is similar to that of TRM, and both spectra are different from the coercivity spectrum of Isr. The use of ARM instead of TRM to determine palaeo‐intensities is discussed in relation to the results obtained. During high‐ and low‐temperature treatment ARM behaves similarly to Isr but unlike TRM for all grain sizes studied. The results of this study are discussed in terms of a remanence composed of PSD surface moments and MD and PSD bulk moments.

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Section: Psd Effectsmentioning

confidence: 68%

“…where it is assumed that these bulk moments are screened by as much as 75 per cent (Merrill 1981). For the MD TRM contiibution, Stacey & Banerjee (1974, p. 109) derive:…”

Section: (5)mentioning

confidence: 99%

TRM, ARM and Isr of two natural magnetites of MD and PSD grain size

Hartstra¹

1983

Geophysical Journal International

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“…Relaxing the idealized assumptions in Runcorn's analysis has subsequently indicated that remanent magnetization may nonetheless be important. The remanent magnetization is not simply proportional to the magnetizing field (Merrill 1981;Merrill and McElhinny 1983), and this non-linearity will yield an external field even for uniform spherical shells (Lesur and Jackson 2000). In addition, Aharonson et al (2004) demonstrated that non-uniformity in the magnetized crustal shell thickness produced by latitudinal and longitudinal thermal variations at Mercury could result in a detectable external field even when the susceptibility is linear.…”

Section: Introductionmentioning

confidence: 96%

The Magnetometer Instrument on MESSENGER

et al. 2007

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The Magnetometer (MAG) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission is a low-noise, tri-axial, fluxgate instrument with its sensor mounted on a 3.6-m-long boom. The boom was deployed on March 8, 2005. The primary MAG science objectives are to determine the structure of Mercury's intrinsic magnetic field and infer its origin. Mariner 10 observations indicate a planetary moment in the range 170 to 350 nT R 3 M (where R M is Mercury's mean radius). The uncertainties in the dipole moment are associated with the Mariner 10 trajectory and variability of the measured field. By orbiting Mercury, MESSENGER will significantly improve the determination of dipole and higher-order moments. The latter are essential to understanding the thermal history of the planet. MAG has a coarse range, ±51,300 nT full scale (1.6-nT resolution), for pre-flight testing, and a fine range, ±1,530 nT full scale (0.047-nT resolution), for Mercury operation. A magnetic cleanliness program was followed to minimize variable and static spacecraft-generated fields at the sensor. Observations during and after boom deployment indicate that the fixed residual field is less than a few nT at the location of the sensor, and initial observations indicate that the variable field is below 0.05 nT at least above about 3 Hz. Analog signals from the three axes are low-pass filtered (10-Hz cutoff) and sampled simultaneously by three 20-bit analog-to-digital converters every 50 ms. To accommodate variable telemetry rates, MAG provides 11 output rates from 0.01 s −1 to 20 s −1 . Continuous measurement of fluctuations is provided with a digital 1-10 Hz bandpass filter. This fluctuation level is used to trigger high-time-resolution sampling in eight-minute segments to record events of interest when continuous high-rate sampling is not possible. The MAG instrument will provide accurate characterization of the intrinsic planetary field, magnetospheric structure, and dynamics of Mercury's solar wind interaction.

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“…An additional complication is the growth of new metamorphic mineralogy in metamorphic rocks under variable metamorphic conditions. Furthermore rocks with certain magnetic mineralogies and grain sizes (multiple domain material) are not necessarily suitable for paleomagnetic investigation (Merrill, 1981). Thus the major task in studying metamorphic rocks is to find a suitable magnetic mineralogy and of sufficiently small grain size (single domain) to have recorded a fossil remanence (Watts, 1982).…”

Section: Introductionmentioning

confidence: 99%

A systematic approach to radiometric and paleomagnetic studies in a mobile orogenic belt: I. The waning phase of activity in the southern Appalachians of South Carolina

Dooley

Manzoni

Nairn

1984

Geophysical Surveys

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Abstract. The survey of radiometric and paleomagnetic work on the mafic rocks of South Carolina is consistent with, and amplifies the studies on the acidic rocks of the southeast by Ellwood (1982). The westerly post-early Mesozoic tilt of the southeastern Appalachians proposed by Dooley and Smith (1982) over most of the Piedmont balances out the post-late Paleozoic southeastern tilt of Ellwood (1982). Only in the Elberton-Sparta block is the tilting important and here the interpretation proposed is of a greater initial tilt (approximately 25-30 ~ reduced by the post-early Mesozoic tilt.There is no evidence of displaced terrains as far as the King's Mountain, Charlotte, and Slate belts are concerned at least since 300 m.y. ago and perhaps as early as 350 m.y. ago. The anomalous paleomagnetic data from the Kiokee belt is best interpreted as due to tectonic displacements associated with the late Paleozoic event described by Secor and Snoke (1978) and Snoke et al, (1980). The paleopoles of the mafic rocks are in agreement with paleopoles on the North American apparent polar wander path (APWP) at about 300m.y. The resolution of K-Ar apparent ages of 350m.y. or older will require 4~ studies and such age relationships are critical to the reasonable application of tilt corrections in the southern Appalachians.

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Toward a better theory of thermal remanent magnetization

Cited by 38 publications

References 58 publications

TRM, ARM and Isr of two natural magnetites of MD and PSD grain size

TRM, ARM and Isr of two natural magnetites of MD and PSD grain size

The Magnetometer Instrument on MESSENGER

A systematic approach to radiometric and paleomagnetic studies in a mobile orogenic belt: I. The waning phase of activity in the southern Appalachians of South Carolina

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