Non-destructive portable gamma ray spectrometry used in provenancing Romangranitoid columns from Leptis Magna, North Africa

Portable gamma ray spectrometry (PGRS) provides a non-destructive means to analyse quantitatively large artefacts, such as building stones for the rad ioelements K, U and Th. Nine Roman granitoid columns at the Leptis Magna Ru ins in Windsor Great Park, London, were measured in situ by PGRS. Correctio ns for the environmental background contribution to the gamma ray flux meas ured, and for the shape and size of the columns, are described. Comparison of the PGRS data with a radioelement data base for Roman granited sources i ndicates that most of the columns originated int he Troad area of Turkey. T wo columns could not be unambiguously provenanced using PGRS alone because there is insufficient difference between radioelement concentrations in cer tain sources. However, non-destructive measurements of magnetic susceptibil ity, used in conjunction with PGRS data, suggest that these two columns ori ginated int he Kozak Dag, also in Turkey.