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Geophysical and petrophysical characterisation of IOCG prospects in northern Sweden
Maersk Olie og Gas AS.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
2008 (English)Conference paper, Presentation (Other academic)
Abstract [en]

In the last decade the importance of Fe-oxide Cu-Au deposits has been increasing constantly and a relevant effort was put on the creation of efficient exploration models. Among the other disciplines, geophysics is a vital tool for the first definition of IOCG leads. Airborne/field geophysical surveys are widely used fro preliminary exploration and they can be further exploited to characterise mineral alterations and to indicate the presence of magnetic or density anomalies. The link between the geophysical signature of altered or mineralised rocks and the alterations/mineralisations themselves is given by the physical properties of rocks. In this study we review this link by investigating in very detail the petrophysical (i.e. magnetic and density) properties of the Tjårroåkka IOCG prospect together with its geophysical expression at the surface. Moreover, we put this prospect in a more regional context with a study that makes use of available airborne magnetic and radiometric data, coupled with ground gravity measurements and petrophysical databeses.Our study suggests that, at semi-regional scale, the Fe-Cu prospects are located at major gravity highs that bound granitic intrusions. The prospects appear to be linked to main faulting and to positive magnetic anomalies caused by magnetite enrichment. At prospect scale, the magnetic print of IOCG deposits may be subdivided as follows: the Fe-prospect is characterised by high magnetic anomalies due to a high content of magnetite, whereas the Cu-mineralised rocks show hematitisation of magnetite, which causes a decrease in magnetic susceptibility. The occurrence of IOCG mineralised rocks is also indicated by the associated potassic alteration, which can be mapped through analysis of airborne radiometric data. In this case, the potassium/thorium ratio has been proven to be a viable attribute to locate K-altered zones.

Place, publisher, year, edition, pages
Research subject
Applied Geophysics
URN: urn:nbn:se:ltu:diva-34238Local ID: 85fc5530-b0c7-11dd-9c9d-000ea68e967bOAI: diva2:1007488
International Geological Congress : 06/08/2008 - 14/08/2008
Godkänd; 2008; 20081112 (ysko)Available from: 2016-09-30 Created: 2016-09-30Bibliographically approved

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