1887
Volume 31, Issue 1-2
  • ISSN: 0812-3985
  • E-ISSN: 1834-7533

Abstract

Magnetic anomalies in the Palaeoproterozoic Willyama Supergroup in the Broken Hill region have a number of different sources, including stratiform magnetite, structurally controlled magnetite and magnetite in igneous rocks. Magnetic sedimentary units are relatively uncommon; most metasedimentary rocks are chemically reduced and host few stratiform anomalies. Exceptions include units within the Paragon Group and volumetrically minor banded iron formation. Structurally controlled anomalies are common across the region and are caused by magnetite in hightemperature shear zones, tectonic fabrics, or in high-strain zones developed along the contact between rocks of contrasting competency. Magnetite formation occurred more than once during the deformational history, during both high-grade and lower-grade metamorphism. Many of the observed linear anomalies coincide with the regional S3 fabric, which formed during upper greenschist to amphibolite-facies metamorphism. Retrograde shear zones are generally magnetite-destructive and form linear zones of low magnetic intensity. Amphibolite has a generally low magnetic susceptibility, although certain units have a high susceptibility, possibly due to alteration as a result of fluid flow. The abundance of structurally controlled anomalies and the relative paucity of stratigraphic anomalies hamper the detailed extrapolation of lithological units beneath cover and means that a ‘magnetic stratigraphy’ is difficult to construct for the Willyama Supergroup. Rather, aeromagnetic data are more useful in the delineation of high-strain zones that have acted as channels for fluid flow, resulting in the formation or destruction of magnetite. Tracing these zones of fluid flow has potential benefits for the reconstruction of mineralising systems and magnetite formed in these zones may have acted as a chemical trap for metals such as gold.

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2000-03-01
2026-01-16

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References

  1. Andrews, E.C., 1922, The geology of the Broken Hill district: Mem. Geol. Surv. NSW, 8, 1-432.
  2. Bradley, G.M., 1984, Mount Gipps 1:25 000 Geological Sheet, 7234-III-S: NSW Geol. Surv., Sydney.
  3. Brown, R.E., 1985, Gairdners Tank 1:25,000 Geological Sheet, 7234-IV-N: NSW Geol. Surv., Sydney.
  4. Gibson, G.M., Drummond, B., Fomin, T., Owen, A., Maidment, D.W., Gibson, D., Peljo, M. and Wake-Dyster, K., 1998a, Re-evaluation of crustal structure in the Broken Hill Inlier through structural mapping and seismic profiling: AGSO Record 1998/11.
  5. Gibson, G.M., Fomin, T., Drummond, B., Owen, A., Maidment, D. and Wake-Dyster, K., 1998b, Structure and tectonic evolution of Broken Hill Inlier revisited in the light of new structural mapping and seismic reflection data: Geol. Soc. Austral., Abstr., 49, 165.
  6. Gibson, G.M., Maidment, D.W. and Haren, R., 1996, Re-evaluating the structure of Broken Hill: AGSO Res. Newsletter, 25, 1-3.
  7. Gibson, G.M., Maidment, D.W. and Haren, R., 1997, Willyama Supergroup, Broken Hill, Australia: a 1600 Ma granulite terrane situated along the Neoproterozoic margin of Gondwana following continental rifting and breakup of Rodinia, in Bradshaw, J.D., Weaver, S.D., Eds., Terrane Dynamics 97, Abstracts of the International conference on Terrane Geology, Christchurch, N.Z., 71-74.
  8. Giddings, J.W., Gibson, G.M. and Maidment, D.W., 1999, Rock-property-structural geology synergy at work in Broken Hill: a case for structural control of linear magnetic anomalies: AGSO Res. Newsletter, 30, 7-10.
  9. Giddings, J., Ruszkowski, P., Gibson, G., Maidment, D. and Rokvic, U., 1998, Petrophysical studies in the Broken Hill Block: implications for magnetic modelling and the control mechanism of linear magnetic anomalies: Abstracts from the 1998 Broken Hill Exploration Initiative meeting. AGSO Record 1998/25, 41-45.
  10. Glen, R.A., Laing,W.P., Parker A.J. and Rutland R.W.R., 1977, Tectonic relationships between the Proterozoic Gawler and Willyama Orogenic Domains, Australia: J. Geol. Soc. Austral., 24, 125-140.
  11. Holser, W.T. and Schneer, C.J., 1953, Deposition of high temperature, non-magmatic magnetite: Econ. Geol., 48, 620.
  12. Laing, W.P., Marjoribanks, R.W. and Rutland, R.W.R., 1978, Structure of the Broken Hill Mine area and its significance for the genesis of the orebodies: Econ. Geol., 73, 1112-1136.
  13. McIntyre, J.I., 1980, Geological significance of magnetic patterns related to magnetite in sediments and metasediments - a review: Austral. Soc. Expl. Geophys. Bull., 11, 19-33.
  14. McPhail, D.C., 1993, The behaviour of iron in high-temperature chloride brines: Geol. Soc. Austral. Abstr., 34, 50-51.
  15. Maidment, D.W. and Gibson, G.M., 1999, Sources of magnetic anomalies in the Broken Hill region, NSW: AGSO Record 1999/6.
  16. Marjoribanks, R.W., Rutland, R.W.R, Glen, R.A. and Laing,W.P., 1980, The structure and tectonic evolution of the Broken Hill region, Australia: Precambrian. Res., 13, 209-240.
  17. Nutman, A.P., and Gibson G.M., 1998, Zircon ages from metasediments, granites and mafic intrusions: reappraisal of the Willyama Supergroup: Abstracts from the 1998 Broken Hill Exploration Initiative meeting. AGSO Record 1998/25, 86-88.
  18. Skirrow, R.G. and Ashley, P.M., 1998, Copper-gold mineral systems and regional alteration, Curnamona Craton: Abstracts from the 1998 Broken Hill Exploration Initiative meeting. AGSO Record 1998/25, 104-108.
  19. Stevens, B.P.J., 1997, Geological controls on magnetite in metasediments, Broken Hill. Broken Hill Exploration Initiative: Abstracts from 1997 Annual Meeting. AGSO Record 1997/49, 38-39.
  20. Stevens, B.P.J., 1998, Investigations of aeromagnetic anomalies at Broken Hill: NSW Dept. Min. Res. Minfo 58, 18-22.
  21. Stevens, B.P.J. and Capnerhurst, K.R.D., 1998, Magmatic and alteration trends identified from the NSWDMR Broken Hill whole rock geochemistry database: Geol. Soc. Austral., Abstr., 49, 14th Australian Geological Convention, Townsville, 430.
  22. Tucker, D.H., 1983, The characteristics and interpretation of regional magnetic and gravity fields in the Broken Hill district: Aus. I.M.M. Conference, Broken Hill. NSW, July 1983, 81-114.
  23. White, S.H., Rothery, E., Lips, A.L.W. and Barclay, T.J.R., 1995, Broken Hill area, Australia, as a Proterozoic fold and thrust belt: implications for the Broken Hill base-metal deposit: Inst. Min. Metall. Trans., 104, B1-B17.
  24. White, S.H., Rothery, E., Lips, A.L.W. and Barclay, T.J.R., 1996, Author's reply to discussion by Stevens, of White et al. 1995: Inst. Min. Met., Trans., 104. B90-98.
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  • Article Type: Research Article
Keyword(s): Broken Hill; geological structure; magnetics; modelling; petrophysics

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