Automatic identification of responses from porphyry intrusive systems within magnetic data using image analysis

Eun-Jung Holden, Shih Ching Fu, Peter Kovesi, Mike Dentith, B. Bourne, M. Hope

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Direct targeting of mineral deposits using magnetic data may be facilitated by hydrothermal alteration associated with the mineralising event if the alteration changes the magnetic properties of the host rock. Hydrothermal alteration associated with porphyry-style mineralisation typically comprises concentric near-circular alteration zones surrounding a roughly circular central intrusion. The intrusion itself and the proximal alteration zone are usually associated with positive magnetic anomalies whilst the outer alteration zones are much less magnetic. Because the country rocks are usually magnetic, this pattern of alteration produces a central magnetic 'high' surrounded by an annular magnetic 'low'.This paper presents an automatic image analysis system for gridded data that provides an efficient, accurate and non-subjective way to seek the magnetic response of an idealised porphyry mineralising system within magnetic datasets. The method finds circular anomalies that are associated with the central intrusion and inner alteration zone of the porphyry system using a circular feature detection method called the radial symmetry transform. Next, their boundaries are traced using deformable splines that are drawn to the locations of maximum contrast between the amplitudes of the central 'high' and surrounding area of lower magnetisation.Experiments were conducted on magnetic data from Reko Diq, Pakistan; a region known to contain numerous occurrences of porphyry-style mineralisation. The predicted locations of porphyry systems closely match the locations of the known deposits in this region.This system is suitable as an initial screening tool for large geophysical datasets, therefore reducing the time and cost imposed by manual data inspection in the exploration process. The same principles can be applied to the search for circular magnetic responses with different amplitude characteristics. (C) 2011 Elsevier B.V. All rights reserved.
Original languageEnglish
Pages (from-to)255-262
JournalJournal of Applied Geophysics
Volume74
DOIs
Publication statusPublished - 2011

Fingerprint

image analysis
porphyry
hydrothermal alteration
intrusion
mineralization
magnetic property
mineral deposit
detection method
country rock
magnetic anomaly
magnetization
host rock
targeting
rocks
symmetry
mineral deposits
Pakistan
transform
magnetic anomalies
splines

Cite this

@article{61de1871f2d145cab2597970f120a41d,
title = "Automatic identification of responses from porphyry intrusive systems within magnetic data using image analysis",
abstract = "Direct targeting of mineral deposits using magnetic data may be facilitated by hydrothermal alteration associated with the mineralising event if the alteration changes the magnetic properties of the host rock. Hydrothermal alteration associated with porphyry-style mineralisation typically comprises concentric near-circular alteration zones surrounding a roughly circular central intrusion. The intrusion itself and the proximal alteration zone are usually associated with positive magnetic anomalies whilst the outer alteration zones are much less magnetic. Because the country rocks are usually magnetic, this pattern of alteration produces a central magnetic 'high' surrounded by an annular magnetic 'low'.This paper presents an automatic image analysis system for gridded data that provides an efficient, accurate and non-subjective way to seek the magnetic response of an idealised porphyry mineralising system within magnetic datasets. The method finds circular anomalies that are associated with the central intrusion and inner alteration zone of the porphyry system using a circular feature detection method called the radial symmetry transform. Next, their boundaries are traced using deformable splines that are drawn to the locations of maximum contrast between the amplitudes of the central 'high' and surrounding area of lower magnetisation.Experiments were conducted on magnetic data from Reko Diq, Pakistan; a region known to contain numerous occurrences of porphyry-style mineralisation. The predicted locations of porphyry systems closely match the locations of the known deposits in this region.This system is suitable as an initial screening tool for large geophysical datasets, therefore reducing the time and cost imposed by manual data inspection in the exploration process. The same principles can be applied to the search for circular magnetic responses with different amplitude characteristics. (C) 2011 Elsevier B.V. All rights reserved.",
author = "Eun-Jung Holden and Fu, {Shih Ching} and Peter Kovesi and Mike Dentith and B. Bourne and M. Hope",
year = "2011",
doi = "10.1016/j.jappgeo.2011.06.016",
language = "English",
volume = "74",
pages = "255--262",
journal = "Journal of Applied Geophysics",
issn = "0926-9851",
publisher = "Elsevier",

}

Automatic identification of responses from porphyry intrusive systems within magnetic data using image analysis. / Holden, Eun-Jung; Fu, Shih Ching; Kovesi, Peter; Dentith, Mike; Bourne, B.; Hope, M.

In: Journal of Applied Geophysics, Vol. 74, 2011, p. 255-262.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Automatic identification of responses from porphyry intrusive systems within magnetic data using image analysis

AU - Holden, Eun-Jung

AU - Fu, Shih Ching

AU - Kovesi, Peter

AU - Dentith, Mike

AU - Bourne, B.

AU - Hope, M.

PY - 2011

Y1 - 2011

N2 - Direct targeting of mineral deposits using magnetic data may be facilitated by hydrothermal alteration associated with the mineralising event if the alteration changes the magnetic properties of the host rock. Hydrothermal alteration associated with porphyry-style mineralisation typically comprises concentric near-circular alteration zones surrounding a roughly circular central intrusion. The intrusion itself and the proximal alteration zone are usually associated with positive magnetic anomalies whilst the outer alteration zones are much less magnetic. Because the country rocks are usually magnetic, this pattern of alteration produces a central magnetic 'high' surrounded by an annular magnetic 'low'.This paper presents an automatic image analysis system for gridded data that provides an efficient, accurate and non-subjective way to seek the magnetic response of an idealised porphyry mineralising system within magnetic datasets. The method finds circular anomalies that are associated with the central intrusion and inner alteration zone of the porphyry system using a circular feature detection method called the radial symmetry transform. Next, their boundaries are traced using deformable splines that are drawn to the locations of maximum contrast between the amplitudes of the central 'high' and surrounding area of lower magnetisation.Experiments were conducted on magnetic data from Reko Diq, Pakistan; a region known to contain numerous occurrences of porphyry-style mineralisation. The predicted locations of porphyry systems closely match the locations of the known deposits in this region.This system is suitable as an initial screening tool for large geophysical datasets, therefore reducing the time and cost imposed by manual data inspection in the exploration process. The same principles can be applied to the search for circular magnetic responses with different amplitude characteristics. (C) 2011 Elsevier B.V. All rights reserved.

AB - Direct targeting of mineral deposits using magnetic data may be facilitated by hydrothermal alteration associated with the mineralising event if the alteration changes the magnetic properties of the host rock. Hydrothermal alteration associated with porphyry-style mineralisation typically comprises concentric near-circular alteration zones surrounding a roughly circular central intrusion. The intrusion itself and the proximal alteration zone are usually associated with positive magnetic anomalies whilst the outer alteration zones are much less magnetic. Because the country rocks are usually magnetic, this pattern of alteration produces a central magnetic 'high' surrounded by an annular magnetic 'low'.This paper presents an automatic image analysis system for gridded data that provides an efficient, accurate and non-subjective way to seek the magnetic response of an idealised porphyry mineralising system within magnetic datasets. The method finds circular anomalies that are associated with the central intrusion and inner alteration zone of the porphyry system using a circular feature detection method called the radial symmetry transform. Next, their boundaries are traced using deformable splines that are drawn to the locations of maximum contrast between the amplitudes of the central 'high' and surrounding area of lower magnetisation.Experiments were conducted on magnetic data from Reko Diq, Pakistan; a region known to contain numerous occurrences of porphyry-style mineralisation. The predicted locations of porphyry systems closely match the locations of the known deposits in this region.This system is suitable as an initial screening tool for large geophysical datasets, therefore reducing the time and cost imposed by manual data inspection in the exploration process. The same principles can be applied to the search for circular magnetic responses with different amplitude characteristics. (C) 2011 Elsevier B.V. All rights reserved.

U2 - 10.1016/j.jappgeo.2011.06.016

DO - 10.1016/j.jappgeo.2011.06.016

M3 - Article

VL - 74

SP - 255

EP - 262

JO - Journal of Applied Geophysics

JF - Journal of Applied Geophysics

SN - 0926-9851

ER -