Magnetization Estimation for Nonuniformly Magnetized Seamounts

Emilia, David A.; Massey, Robert L.

doi:10.1190/1.1440423

Cited by 26 publications

(10 citation statements)

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“…By fixing the moment orientation, it is then natural to require the individual moments to always be nonnegative ( m j ≥ 0 for all j ). This magnetization, which is unidirectional (uniform in direction) but nonuniform in intensity [ Emilia and Massey , 1974; McNutt , 1986; Parker , 1991], has and where the entries in A are now given by: We see that for all j , so that although we still have M = P measurements, we now have only N = Q parameters to fit because of the 2 Q additional constraints imposed by (9). Note that by requiring the moments to be unidirectional and nonnegative, there is no longer a guarantee that a solution exists whose residual RMS is less than our measurement uncertainty [ Parker , 1991].…”

Section: Least Squares Methodsmentioning

confidence: 99%

Paleomagnetic analysis using SQUID microscopy

et al. 2007

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[1] Superconducting quantum interference device (SQUID) microscopes are a new generation of instruments that map magnetic fields with unprecedented spatial resolution and moment sensitivity. Unlike standard rock magnetometers, SQUID microscopes map magnetic fields rather than measuring magnetic moments such that the sample magnetization pattern must be retrieved from source model fits to the measured field data. Here we present the first direct comparison between paleomagnetic analyses on natural samples using joint measurements from SQUID microscopy and moment magnetometry. We demonstrate that in combination with a priori geologic and petrographic data, SQUID microscopy can accurately characterize the magnetization of lunar glass spherules and Hawaiian basalt. The bulk moment magnitude and direction of these samples inferred from inversions of SQUID microscopy data match direct measurements on the same samples using moment magnetometry. In addition, these inversions provide unique constraints on the magnetization distribution within the sample. These measurements are among the most sensitive and highest resolution quantitative paleomagnetic studies of natural remanent magnetization to date. We expect that this technique will be able to extend many other standard paleomagnetic techniques to previously inaccessible microscale samples.

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Section: Least Squares Methodsmentioning

confidence: 99%

Paleomagnetic analysis using SQUID microscopy

et al. 2007

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“…The performance of this method is highly dependent on the correct position of the centre and on the determination of the major and minor axes of the body. Emilia and Massey (1974) developed an iterative method for estimating the vertical magnetization distribution of seamounts. This method approximates the seamounts by vertically juxtaposed right prisms with polygonal horizontal cross sections, which have the same magnetization direction and different magnetization intensities.…”

Section: C Oliveira Jr Et Al: Magnetization Direction Of Spherimentioning

confidence: 99%

Estimation of the total magnetization direction of approximately spherical bodies

Oliveira

Sales

Barbosa

et al. 2015

Nonlin. Processes Geophys.

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Abstract.We have developed a fast total-field anomaly inversion to estimate the magnetization direction of multiple sources with approximately spherical shapes and known centres. Our method is an overdetermined inverse problem that can be applied to interpret multiple sources with different but homogeneous magnetization directions. It requires neither the prior computation of any transformation-like reduction to the pole nor the use of regularly spaced data on a horizontal grid. The method contains flexibility to be implemented as a linear or non-linear inverse problem, which results, respectively, in a least-squares or robust estimate of the components of the magnetization vector of the sources. Applications to synthetic data show the robustness of our method against interfering anomalies and errors in the location of the sources' centre. Besides, we show the feasibility of applying the upward continuation to interpret non-spherical sources. Applications to field data over the Goiás alkaline province (GAP), Brazil, show the good performance of our method in estimating geologically meaningful magnetization directions. The results obtained for a region of the GAP, near to the alkaline complex of Diorama, suggest the presence of non-outcropping sources marked by strong remanent magnetization with inclination and declination close to −70.35 and −19.81 • , respectively. This estimated magnetization direction leads to predominantly positive reduced-to-the-pole anomalies, even for other region of the GAP, in the alkaline complex of Montes Claros de Goiás. These results show that the non-outcropping sources near to the alkaline complex of Diorama have almost the same magnetization direction of those ones in the alkaline complex of Montes Claros de Goiás, strongly suggesting that these sources have been emplaced in the crust within almost the same geological time interval.

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“…The determination of magnetic paleopoles from seamount magnetic anomalies constitutes the major data source for the Pacific Apparent Polar Wander Path (APWP); Emilia & Massey (1974); Hilderbrand & Parker (1987); Gee et al (1989); Sager & Koppers (2000); Lee et al (2003); Kubota & Uchiyama (2005). In these cases the bathymetry provides an immediate constrain for the geometry of the magnetic sources, i.e., the submarine volcanic cones.…”

Section: Introductionmentioning

confidence: 99%