International Journal of Scientific & Technology Research

IJSTR@Facebook IJSTR@Twitter IJSTR@Linkedin
Home About Us Scope Editorial Board Blog/Latest News Contact Us

IJSTR >> Volume 5 - Issue 3, March 2016 Edition

International Journal of Scientific & Technology Research  
International Journal of Scientific & Technology Research

Website: http://www.ijstr.org

ISSN 2277-8616

Comparing Seismic And Magnetic Responses To Copper Gold Deposits Under Different Cover Sequences

[Full Text]



Okan Evans Onojasun



Cu-Au deposits, exploration, magnetic method, resolution, seismic method



Appropriate application of geophysical techniques is required to effectively explore through the cover sequences that will allow the discovery of deep seated orebodies within the 1-3km depth range. Whilst potential field methods that are traditionally used for Cu-Au exploration seems effective, they lack the expected resolution required to detect deeper mineral deposits under >500 m cover. Seismic reflection techniques offers a distinct advantage over all other geophysical techniques because of its ability to penetrate deeper into the subsurface without losing its resolution. We present in this report modelling results from magnetic and seismic responses to Cu-Au deposits when located within 100-1000m depth range. In the case of magnetic modelling, we apply upward continuation filters which calculate the potential field that would have been recorded at (100m, 250m, 500m and 1000 m) levels by filtering away shallow anomalies from the initial data. For seismic modelling, simple but realistic geological model with varying cover thicknesses (100m, 250m, 500m and 1000m) were created, and then populate these models with petrophysical data. Simulated synthetic seismic responses from the models was processed using basic processing flows to obtained depth migrated images. Results show that for shower depths (0-100m), good correlation exist between the magnetic and the seismic responses. From 100-250m depth cover, though we can still see some magnetic anomalies within the target zone, its effectiveness decreases with depths whereas seismic responses was maintain within the depth range. From 500m to 1000m magnetic response becomes spear or fuzzy as much useful information is practically missed out. Similarly, high resolution power of seismic was ably demonstrated as the depth of even 2km did not degrade its resolution. Thus, both magnetic and seismic methods are very useful for shallow investigation but at greater depth, seismic method appears to be a more valid exploration tool to find Cu-Au deposits.



[1] M.D. Barton, and D.A. Johnson, “Footprints of Fe-oxide (-Cu-Au) systems.” SEG 2004 Predictive Mineral Discovery Under Cover – Extended Abstracts, Centre for Global Metallogeny, The University of Western Australia, v. 33, p. 112-116

[2] S.J. Daly, C.M. Fanning, and M.C. Fairclough, “Tectonic evolution and exploration potential of the Gawler Craton”, South Australia AGSO Journal of Australian Geology & Geophysics, 17: 145-168, 1998

[3] B.J. Drummond, B.R. Goleby, A.J. Own, A.N. Yeates, C. Swager, Y. Zhang, and J.K. Jackson, “Seismic reflection imaging of mineral systems”, Three case histories: Geophysics, 65, 1852- 1861, 2000

[4] W. Duweke, J.C. Trickett, K. Tootal, and M. Slabbert, “Three dimensional reflections seismic as a tool to optimize mine design, planning and development in the Bushveld igneous complex”, 64th EAGE Conference and Exhibition, Florence, Italy, May 27-30, Extended Abstracts, p. D-20, 2002

[5] K. Ehrig, J. McPhie, and V. Kamenetsky, “Geology and mineralogical zonation of the Olympic Dam iron oxide Cu-U-Au-Ag deposit”, South Australia. Society of Economic Geologists Special Publication, 16, 237-268, 2013

[6] G. Fraser, S. McAvaney, N. Neumann, M. Szpunar, and A. Reid, “Discovery of early Mesoarchaean crust in the eastern Gawler Craton”, South Australia; Precambrian Research, 179, 1-21, 2010

[7] M. Hand, A.J. Reid, and L. Jagodzinski, “Tectonic framework of the Gawler Craton, South Australia”, Economic Geology, 102, 1377-1395, 2007

[8] C. Juhlin, and H. Palm, “Experiences from Shallow Reflection Seismic over Gra-nitic Rocks”, in Sweden in Eaton, D.W., Milkereit, B. and Salisbury, M.H. (eds.) Hard rock Seismic Exploration. SEG Developments in Geophysics Series, 93-109, 2003

[9] Malehmir et al. Review paper in GP special issues, 2014

[10] A. Malehmir, C. Juhlin, C. Wijns, M. Urosevic, P. Valasti, and E. Koivisto, “3D reflection seismic imaging for open-pit mine planning and deep exploration in the Kevitsa Ni-Cu-PGE deposit”, northern Finland. Geophysics, 77(5): WC95-WC108, 2012

[11] A.J. Parker, “Precambrian provinces of South Australia; tectonic setting” In: Hughes, F.E. (Ed.) Geology of the mineral deposits of Australia and Papua New Guinea; Volume 2. Monograph Series - Australasian Institute of Mining and Metallurgy. Australasian Institute of Mining and Metallurgy, Melbourne, Victoria, Australia, pp. 985-990, 1990

[12] A.J. Parker, S.J. Daly, D.J. Flint, R.B. Flint, W.V. Preiss, and G.S. Teale, “Paleoproterozoic” In: J.F. Drexel, W.V. Preiss and A.J. Parker (Editors), the geology of South Australia; Volume 1, The Precambrian; Bulletin Geological Survey of South Australia. Geological Survey of South Australia, Adelaide, South Aust., Australia, pp. 50-105, 1993

[13] C.C. Pretorius, W.F. Trewick, A. Fourie, and C. Irons, “Application of 3-D seismic to mine planning at Vaal Reef's gold mine”, number 10 shafts, Republic of South Africa: Geophysics, 65, 1862-1870, 2000

[14] D.E. Roberts, and G.R.T Hudson, “The Olympic Dam copper-uranium-gold deposit”, Roxby Downs, South-Australia: Economic Geology and the Bulletin of the Society of Economic Geologists, v. 78, p. 799–822, doi:10.2113/gsecongeo.78.5.799, 1983

[15] M.H. Salisbury, B. Milkereit, G.L. Ascough, R. Adair, D. Schmitt, and L. Matthews, “Physical properties and seismic imaging of massive sulphides” in Canada, P.a.D.A.o., eds., Geophysics and Geochemistry at the Millennium, 383-390, GEO F/X Division of AG Information Systems Ltd., 1997

[16] J.J Vassallo, and C.J.L. Wilson, “Paleoproterozoic regional-scale non-coaxial deformation; an example from eastern Eyre Peninsula” South Australia Journal of Structural Geology, 24: 1-24, 2002

[17] P.J. Williams, and R.G. Skirrow, “Overview of iron oxide-copper gold deposits in the Curnamona Province and Cloncurry District (Eastern Mount Isa Block)”, in Porter, T.M., ed., Hydrothermal iron oxide copper-gold and related deposits: A global perspective: PGC Publishing, Adelaide, v. 1, p. 105-122, 2000