HR: 0800h
AN: MR11A-0933    [Abstracts]
TI: Physical Properties of Rocks and Geophysical Data as Tools for Targeting Fe-Oxide Cu-Au Mineralisations in Northern Sweden
AU: Berggren, R
EM: robert.berggren@ltu.se
AF: Division of Ore Geology and Applied Geophysics, Lulea University of Technology, Lulea, SE-97187 Sweden
AU: * Sandrin, A
EM: ALSA@geol.ku.dk
AF: Geological Institute, University of Copenhagen, Oster Voldgade 10, Copenhagen, DK-1350 Denmark
AU: Elming, S
EM: Sten-Ake.Elming@ltu.se
AF: Division of Ore Geology and Applied Geophysics, Lulea University of Technology, Lulea, SE-97187 Sweden
AB: It is well documented that ore mineralisations are frequently associated with various types of rock alterations. These rock alterations may affect in different extents the physical properties of rocks. The present work focuses on the petrophysical and geophysical properties of Fe-oxide Cu-Au mineralisations (IOCG) in the western Kiruna mining district, northern Sweden, with special attention to the Tjarrojakka IOCG mineralisations. Exploration models developed in different areas worldwide (e.g. Australia, Canada) show that IOCG mineralisations are preferentially located in proximity of faults associated with deformation zones of regional relevance, and that IOCG mineralisations are hosted in areas affected by potassic to sodic alteration. This study indicates that at semi-regional scale IOCG mineralisations are located within areas of high gravity anomalies, high values of calculated K content and high K/Th ratios (from airborne radiometric data), which is expression of potassic alteration. In addition to this, extremely high magnetic anomalies situate Fe-oxide (magnetite) occurrences, while low linear magnetic anomalies mark fault/shear zones, in proximity of which the majority of the IOCG-mineralisations are found. At local scale, the IOCG mineralisations of Tjarrojakka are associated with high magnetic and gravity anomalies and high values of the K/Th ratio. Combined petrophysical and geochemical analysis indicate that ferromagnetic minerals (Ti-magnetite) are widely present in the area, together with an alteration phase that is interpreted as Ti-haematite. Cu-sulphides occurrences seem to be related to potassic altered zones, as suggested by Ba enrichment.
DE: 8010 Fractures and faults
DE: 5199 General or miscellaneous
DE: 3665 Mineral occurrences and deposits
DE: 1219 Local gravity anomalies and crustal structure
DE: 1540 Rock and mineral magnetism
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting