Non-destructive potassium measurement in minerals by gamma-ray spectrometry: Toward an enhanced K-Ar dating method

Abstract

Copyright © 2015 by The Geochemical Society of Japan. (McDougall, 1985); and quantifying volcanic risk up to historical times (Gillot et al., 1982; Quidelleur et al., 2001). One of the main sources of uncertainties in the K-Ar dating method is that K and Ar are measured on two separated aliquots of the same sample. Potassium is separated by chemical way and measured by atomic absorption spectroscopy (AAS), while argon is measured by gas source mass spectrometry. This method creates a large undeterminable internal error if the sample is chemically heterogeneous or zoned. To minimize sources of uncertainties, fresh rock specimen have to be selected and a strict mineralogical control has to be carried out to homogenize, as possible, the sample (Gillot et al., 2006). Here we present a different non-destructive technique to measure the K amount at 2s confidence level in minerals and groundmass. Measurement of potassium is carried out with the last generation of high-purity Germanium gamma-ray spectrometer with no chemical preparation of the sample. This non-destructive technique has the advantage to use the same sample aliquot to measure K and 40Ar*. Our approach consists in measuring directly Non-destructive potassium measurement in minerals by gamma-ray spectrometry: Toward an enhanced K-Ar dating method