The Qmeter – a portable tool for remanence and susceptibility

Abstract

Breiner (1973) described a method to separate induced magnetisation from remanent magnetisation of a drill core or hand sample using a total field magnetometer, thereby allowing the Königsberger ratio (Q) to be calculated. However, the method does not seem to be in general use, and nor has there been any improvement to the method despite recent developments that greatly facilitate data acquisition using handheld devices or notebook computers. Here a new fluxgate based pendulum instrument is described that allows a more controlled implementation of Breiner (1973)'s method. The instrument accommodates samples of varying sizes although best results are yielded using regular, cubic or cylindrical, shaped samples. The instrument is portable and powered from a USB port of a notebook or similar computer. Sensitivity is high enough to yield accurate results for rocks that cause significant magnetic anomalies (~Am-1). However, for high Q rocks susceptibility is lost in the noise, and likewise for low Q rocks, remanence is lost in the noise. The instrument is designed to quickly screen core samples at the drill site, or in a core shed, to alert the exploration team if significant remanence is present in which case the magnetic model of the target may require reconsidering. The instrument is not a replacement for laboratory measurements but potentially should save exploration costs by indicating when laboratory measurements should be undertaken.