MINERALOGY OF MAGNETIC SOILS AT A UXO REMEDIATION SITE IN KAHO'OLAWE HAWAII

Magnetic characteristics of soils can have a profound influence on electromagnetic sensors for the detection of unexploded ordnance (UXO) and may cause false alarms in the case of spatially variable concentrations. In particular, the performance of several electromagnetic sensors is hampered by viscous remanent magnetism, which is caused by the presence of ferrimagnetic iron oxide minerals of different sizes and shapes. Tropical soils formed on basaltic substrates commonly have large concentrations of iron oxide minerals. To improve detection and discrimination of UXO in these soils it is crucial to have a better understanding of the types of minerals responsible for the magnetic behavior, as well as their distribution in space. In this paper we present the results of recent field and laboratory studies of soil magnetic properties and soil mineralogy at the former Naval training range on Kaho'olawe Island, Hawaii. We discuss the role of environmental controls such as parent material, age and precipitation on the magnetic properties.