Rock-magnetic properties, oxide mineralogy, and mineral chemistry in relation to aeromagnetic interpretation and the search for ilmenite reserves

Abstract

The understanding of the rock-magnetic properties of the various oxide ores and country rocks in the vicinity of the Tellnes Deposit is a first step toward a successful interpretation of the aeromagnetic maps (NGU Report 96.059) Specifically it has been made obvious that the region contains rocks with very high magnetic susceptibility and low remanence giving rise to large positive induced aeromagnetic anomalies, and it also contains rocks with very strong reversed remanent magnetization giving rise to large negative magnetic anoma- lies. Measured Q values in the region range from 0.1 to 159, supporting the interpretation that both remanent and induced aeromagnetic anomalies were recorded in the region. Samples from selected anomalies were further measured to characterize their rock magnetic properties and to aid in identifying the magnetic minerals in the different rock bodies that are attributed to creating the magnetic anomalies. In selected samples detailed reflected-light micros- copy was performed to identify the magnetic minerals. A subset of these samples was chosen for microprobe analyses. The chemical composition of the samples were correlated with the mineral phases, exsolution and oxidation- exsolution phases.