New approaches to dealing with remanence: magnetic moment analysis using tensor invariants and remote determination of in situ magnetisation using a static tensor gradiometer

David A. Clark

doi:10.1071/ASEG2013ab049

ISSN: 2202-0586
E-ISSN:

oa New approaches to dealing with remanence: magnetic moment analysis using tensor invariants and remote determination of in situ magnetisation using a static tensor gradiometer
Authors David A. Clark^a
View Affiliations Hide Affiliations

^a CSIRO Materials Science and Engineering & CSIRO Earth Science and Resource Engineering, PO Box 218, Lindfield, , NSW, 2070, , Australia, [email protected]
Publisher: Australian Society of Exploration Geophysicists
Source: ASEG Extended Abstracts, Volume 2013, Issue ASEG2013 - 23rd Geophysical Conference, Dec 2013, p. 1 - 7
DOI: https://doi.org/10.1071/ASEG2013ab049
- Published online: 01 Dec 2013

Abstract

Assuming without evidence that magnetic sources are magnetised parallel to the geomagnetic field can seriously mislead interpretation and can result in drill holes missing their targets. I present two new methods for providing information about magnetisation of anomaly sources, independent of the geometry of the causative bodies. The first method is based on analysis of magnetic gradient tensor data. Integral moments of tensor invariants locate the horizontal and vertical centres of magnetisation and estimate the magnetisation direction. The depth estimate allows correction of the integral moments for the finite range of integration, which can accordingly be restricted to the main part of the anomaly. This reduces interference from neighbouring sources. This method provides information on location, total magnetic moment (magnetisation × volume), and magnetisation direction of a compact source, without making any assumptions about its shape.

The second method employs a single combined gradiometer/magnetometer, operating in base station mode within a magnetic anomaly of interest. The response to geomagnetic time variations allows the contributions of induced magnetisation and remanence to the anomaly to be separated. This method allows remote estimation, prior to drilling of (i) the total magnetisation direction of the source, which is a key to accurate modelling (ii) the remanence direction, which can provide geological information such as age of intrusion or alteration, (iii) the Koenigsberger ratio Q, which is indicative of the magnetic mineralogy of the source. If the source is compact, the method also provides a direct indication of the direction to its centroid.

Article metrics loading...

/content/journals/10.1071/ASEG2013ab049

2013-12-01

2026-01-14

From This Site

/content/journals/10.1071/ASEG2013ab049

dcterms_title,dcterms_subject,pub_keyword

-contentType:Journal -contentType:Contributor -contentType:Concept -contentType:Institution

10

5

Full text loading...

References

Beiki, M., Clark, D.A., Austin, J.R. and Foss, C.A., 2012a, Estimating source location using normalized magnetic source strength calculated from magnetic gradient tensor data: Geophysics, 77(6), J23-J37.
Caratori Tontini, F. and Pedersen, L.B., 2008, Interpreting magnetic data by integral moments: Geophysical Journal International, 174, 815-824.
Clark, D.A., 2012a, New methods for interpretation of magnetic gradient tensor data: ASEG 22nd International Geophysical Conference and Exhibition, 26-29 February 2012, Brisbane, Australia, Expanded Abstracts, 11p.
Clark, D.A., 2012b, New methods for interpretation of magnetic vector and gradient tensor data I: eigenvector analysis and the normalised source strength: Exploration Geophysics, 43, 267-282, doi:10.1071/EG12020.
Clark, D.A., 2012c, Interpretation of the magnetic gradient tensor and normalized source strength applied to the Tallawang magnetite skarn deposit, New South Wales, Australia: Society of Exploration Geophysicists Annual Meeting, Las Vegas, Expanded Abstracts, 4p.
Clark, D.A., Schmidt, P.W., Coward, D.A. and Huddleston, M.P., 1998. Remote determination of magnetic properties and improved drill targeting of magnetic anomaly sources by Differential Vector Magnetometry (DVM): Exploration Geophysics, 29, 312-319.
Clark, D.A., Young, J.A. and Schmidt, P.W., 2009, Magnetic Tensor Gradiometry in the Marine Environment: Correction of Electric And Magnetic Field And Gradient Measurements in a Conductive Medium and Improved Methods for Magnetic Target Location Using the Magnetic Gradient Tensor: MARELEC (Marine Electromagnetics) Conference, Stockholm, July, 2009, 10p.
Foss, C., 2006. Strategies to manage remanence effects in magnetic inversion. SEG Expanded Abstracts, 25, 938-942. Helbig, K., 1963. Some integrals of magnetic anomalies and their relation to the parameters of the disturbing body: Zeitschrift für Geophysik, 29, 83-96.
Li, Y., Shearer, S., Haney, M. and Dannemiler, N., 2004. Comprehensive approaches to the inversion of magnetic data with strong remanent magnetization: SEG Expanded Abstracts, 23, 1191-1194.
Pedersen, L.B. and Rasmussen, T.M., 1990. The gradient tensor of potential field anomalies: Some implications on data collection and data processing of maps: Geophysics, 55, 1558- 1566.
Phillips, J.D., 2005. Can we estimate total magnetization directions from aeromagnetic data using Helbig’s integrals?: Earth Planets Space, 57, 681-689.
Phillips, J.D., Nabighian, M.N., Smith, D.V. and Li, Y., 2007. Estimating locations and total magnetization vectors of compact magnetic sources through combined Helbig and Euler analysis: SEG Expanded Abstracts, 26, 770-774.
Pilkington, M. and Beiki, M., 2012. Mitigating remanent magnetization effects in magnetic data using the normalized source strength. SEG Technical Program Expanded Abstracts 2012, 4p.
Pratt, D.A., McKenzie, K.B. and White, A.S., 2012. The remote determination of magnetic remanence. ASEG 22nd International Geophysical Conference and Exhibition, 26-29 February 2012, Brisbane, Australia, Expanded Abstracts, 5p.
Schmidt, P.W. and Clark, D.A., 1997. Directions of magnetization and vector anomalies derived from total field surveys. Preview, 70, 30-32.
Schmidt, P.W. and Clark, D.A., 1998. The calculation of magnetic components and moments from TMI: A case history from the Tuckers igneous complex, Queensland. Exploration Geophysics, 29, 609-614.
Young, J.A., S.T. Keenan, D.A. Clark, K.E. Leslie, P. Sullivan, P. Fairman, C. Williams, C.P. Foley and S.D. Billings, 2010. A Superconducting Magnetic Tensor Gradiometer for Underwater UXO Detection [Extended Abstract]: 21st International Geophysical Conference & Exhibition (ASEG-PESA 2010); Sydney, 4p.

/content/journals/10.1071/ASEG2013ab049

Article Type: Research Article

Keyword(s): geomagnetic variations; magnetisation; normalised source strength; remanence; tensor invariants

Most Cited This Month Most Cited RSS feed

- Inversion of data from electrical imaging surveys in water-covered areas
  
  Authors M. H. Loke and J. W. Lane
- Inversion of Magnetic Data from Remanent and Induced Sources
  
  Authors Robert G. Elllis, Barrry de Wet and Ian N. Macleod
- A comparison of smooth and blocky inversion methods in 2-D electrical imaging surveys
  
  Authors M. H. Loke, Ian Acworth and Torleif Dahlin
- Designing matched bandpass and azimuthal filters for the separation of potential-field anomalies by source region and source type
  
  Authors Jeffrey D. Phillips
- Bad Colour Maps Hide Big Features and Create False Anomalies
  
  Authors Peter Kovesi
- Practical 3D EM inversion – the P223F software suite
  
  Authors Art Raiche, Fred Sugeng and Glenn Wilson
- Estimating Noise Levels in AEM Data
  
  Authors Andy Green and Richard Lane
- Target delineation using Full Tensor Gravity Gradiometry data
  
  Authors Colm A. Murphy and James Brewster
- Transdimensional Monte Carlo Inversion of AEM Data
  
  Authors Ross C Brodie and Malcolm Sambridge
- The geotech VTEM time domain helicopter em system
  
  Authors Ken Witherly, Richard Irvine and Edward Morrison
More Less

oa New approaches to dealing with remanence: magnetic moment analysis using tensor invariants and remote determination of in situ magnetisation using a static tensor gradiometer

Abstract

Most Read This Month

Most Cited This Month Most Cited RSS feed