Chapter 4: Crustal studies using magnetic data

The presented work examines application of an Augmented Iteratively Re-weighted and Refined Least Squares method (AIRRLS) to construct a 3D magnetic susceptibility property from potential field magnetic anomalies. This algorithm replaces an lp minimization problem by a sequence of weighted linear systems in which the retrieved magnetic susceptibility model is successively converged to an optimum solution, while the regularization parameter is the stopping iteration numbers. To avoid the natural tendency of causative magnetic sources to concentrate at shallow depth, a prior depth weighting function is incorporated in the original formulation of the objective function. The speed of lp minimization problem is increased by inserting a pre-conditioner conjugate gradient method (PCCG) to solve the central system of equation in cases of large scale magnetic field data. It is assumed that there is no remanent magnetization since this study focuses on inversion of a geological structure with low magnetic susceptibility property. The method is applied on a multi-source noise-corrupted synthetic magnetic field data to demonstrate its suitability for 3D inversion, and then is applied to a real data pertaining to a geologically plausible porphyry copper unit. The real case study located in Semnan province of Iran consists of an arc-shaped porphyry andesite covered by sedimentary units which may have potential of mineral occurrences, especially porphyry copper. It is demonstrated that such structure extends down at depth, and consequently exploratory drilling is highly recommended for acquiring more pieces of information about its potential for ore-bearing mineralization.

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Profiles of gamma-ray and magnetic data from aerial surveys over the conterminous United States

Data Series ◽

10.3133/ds31 ◽

1999 ◽

Cited By ~ 1

Author(s):

Joseph S. Duval ◽

Frederic E. Riggle

Keyword(s):

United States ◽

Gamma Ray ◽

Magnetic Data ◽

Aerial Surveys

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High-Resolution Seismic-Reflection and Marine Magnetic Data Along the Hosgri Fault Zone, Central California

Open-File Report ◽

10.3133/ofr20091100 ◽

2009 ◽

Author(s):

Ray W. Sliter ◽

Peter J. Triezenberg ◽

Patrick E. Hart ◽

Janet T. Watt ◽

Samuel Y. Johnson ◽

...

Keyword(s):

High Resolution ◽

Fault Zone ◽

Seismic Reflection ◽

Magnetic Data ◽

Central California

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High-resolution seismic data and bathymetric, gravimetric, and magnetic data from the northern Gulf of Mexico collected during R/V Gyre cruise G-81-6

Open-File Report ◽

10.3133/ofr82842 ◽

1982 ◽

Author(s):

J.L. Kindinger ◽

C.E. Stelting ◽

R.J. Miller

Keyword(s):

High Resolution ◽

Gulf Of Mexico ◽

Seismic Data ◽

Magnetic Data ◽

Northern Gulf Of Mexico

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Airborne geophysical surveys in Greenland in 1998

Geological Survey of Denmark and Greenland Bulletin ◽

10.34194/ggub.v183.5202 ◽

1999 ◽

pp. 34-38 ◽

Cited By ~ 2

Author(s):

Thorkild M. Rasmussen ◽

Leif Thorning

Keyword(s):

High Resolution ◽

Geophysical Data ◽

Digital Data ◽

Geological Survey ◽

Magnetic Data ◽

Magnetic Survey ◽

Original Series ◽

Geophysical Surveys ◽

The Government

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Rasmussen, T. M., & Thorning, L. (1999). Airborne geophysical surveys in Greenland in 1998. Geology of Greenland Survey Bulletin, 183, 34-38. https://doi.org/10.34194/ggub.v183.5202 _______________ Airborne geophysical surveying in Greenland during 1998 consisted of a magnetic project referred to as ‘Aeromag 1998’ and a combined electromagnetic and magnetic project referred to as ‘AEM Greenland 1998’. The Government of Greenland financed both with administration managed by the Geological Survey of Denmark and Greenland (GEUS). With the completion of the two projects, approximately 305 000 line km of regional high-resolution magnetic data and approximately 75 000 line km of detailed multiparameter data (electromagnetic, magnetic and partly radiometric) are now available from government financed projects. Figure 1 shows the location of the surveyed areas with highresolution geophysical data together with the area selected for a magnetic survey in 1999. Completion of the two projects was marked by the release of data on 1 March, 1999. The data are included in the geoscientific databases at the Survey for public use; digital data and maps may be purchased from the Survey.

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